NORMAL DEVELOPMENT
neurulation - at 2wks neural plate appears dorsal on disk
neural groove at 18 days, lat neural folds then thicken
neural tube closes at hindbrain and zippers to both ends
Tube consticts & bends into 3 then 5 parts
Telencephalon to cerebral heispheres
Diencephalon to thalami
Mesencephalon to midbrain (remains undivided thruout)
Metencephalon to pons & cb
Myelencephalon to medulla

1. Disjunction - neural & cutaneous ectoderm seperate at 7wks

2. Germinal Matrix - forms neurons & glia from 7 to 30 wks
develops from lining of lat & 3rd vents
neurons migrate to layer 6 first & layer 2 last
Lissencephaly, schizencephaly, heterotopia, polymicrogyr

3. Commisures - form at 8-17wks, lamina term most important
Corpus largest, forms front to back except rostrum last

4. Myelination - Oligodendrocytes production peak 30wk to 8mo
best seen on T2 - myelin is darker than adjacent gray
Birth - dorsal medulla, Cb peduncles & internal capsule
3mo - ventral medulla, deep Cb white matter, corticospinal tracts
4mo - first appearance of myelin in splenium of corpus callosum
6mo - deep cerebral white matter in predominately front to back pattern
8mo - near adult, only frontal tracts & association tracts near trigone left

DISORDERS OF NEURAL TUBE CLOSURE
Dorsal induction - 4-7wks

CHIARI MALFORMATIONS
1. Chiari I - congenital tonsilar ectopia, present as adults
Peglike cb tonsils extend into spinal canal
<6mm N in kids, decreases to 4mm in elderly
5-10mm often asym, >12mm always symtomatic
sx mimic demylinating dz in brainstem & cb deficeincy
not assoc w other brain anomalies, cord anomalies poss
Syrinx - seen in 50%, 90% if symptomatic
Hydromyelia - fluid distention of central canal
Syringomyelia - CSF dissected into paracentral cav
Skull Base Anomalies - 25%, platybasia, basilar invag
atlatooccipital fusion, fused cerv vert (Klippel-Feil)
Hydrocephalus - mild to moderate in 25%, much less than Chiari II
Sx - 40% have Nystagmus, Ataxia & Cb signs
Downbeat Nystagmus most specific, least common
Cranial Nerve Compression - often presenting Sx in Adults
DDx - Tumor of cord, can have cystic portion sim to syrinx
10% have ectopic tonsils

2. Chiari II - complex w skull, dura, brain, spine & cord
Mylomeningocele virtually always present
caused by dorsal openings left during tube closure
embryonic vent system collapses from leaks
low P causes poor distention, sm post fossa results
Dysplastic Tentorium caused by downward hern of cb & stem
dysplastic & fenestrated falx
Tonsils & choroid cascade to C4, Cb extends ant
Lg foramen magnum from downward hern of vermis & stem
Hindbrain Dysfunction - 30% symptomatic, cause death in 10%
CN palsy assoc w stem compression
Kink in medulla & spur formation as low as T1
Syrinx present in >50%
Diastematomyelia - 40% have split spinal cord
Brain Abnormalities - Tectal beaking, lg massa intermedia
Callosal Agenesis - gyri radiate like spokes & Interdigitate
Polymicrogyria & ectopia are common, tethered cord freq
Hydrocephalus in 90%, 4th vent elongated & tubelike
Macrocephaly assoc
Lukenschadel - Lacunar skull in 85%, prom at torcula herophili, gone by 6mo
Segmentation anomalies of C-spine less common than Chiari I
C2-3 fusion most common, bony post arch of C1 absent in 70%
atlanto-occipital fusion rare

3. Chiari III - Chiari II + hindbrain herniation
cb, occip lobes, medulla & pons freq in encephalocele
tissue grossly abn w nec, gliosis & heterotopias
MR good for delineating venous drainage & anatomy
4th & lat vents can be included
AFIP says it should occur at craniovert jxn below occ
CEPHALOCELE'S
A skull defect w herniated intercranial contents
meningocele - leptomeninges & CSF only
meningoencephalocele - brain included, usually abn
Meckle syndrome - only syn assoc w cepaloceles, occiput
cystic dysplastic kidneys & cardiac anom also
congenital always midline, amniotic bands & trauma lat
contain ependyma lined CSF spaces often

1. Occipital Cephaloceles - 70-80%, female predominance
occur between foramen magnum & lambda suture
assoc w Chiari, Dandy, Kippel-Feil, diastematomyelia,
lobar holoprosencephaly & cb dysplasias (tube closure)

2. Parietal Cephaloceles - 10-15%, male predominance
occur between lambda suture & bregma
assoc w Ciari, Dandy, lobar holoprosencephaly &
Corpus Callosum defects (midline brain anomalies)

3. Transphenoidal Cephalocele - 10%, assoc w sellar abn
endocrine abn & callosal agenesis also freq assoc
Coloboma of retina, incomplete closure of choroidal fissure assoc

4. Sincipital or Nasoethmoidal Cephaloceles - 15%, #1 in Asians
between nasal & ethmoid bones, NO syndrome assoc
Crista galli absent, foramen cecum enlarged
orbits displaced lat, ethmoids displaced inf
may enlarge rapidly if lg cystic component
Embryology - a dural divertic connects ectoderm of nose & brain
if this fails to regress this & other anomalies occur
dermoid, dermal sinus, nasal gliomas also
If crista galli present but split it is a dermoid
If crista galli absent & foramen cecum enlarged = cephalocele
Lucent midline N at birth due to cartilage

5. Nasofrontal Cephaloceles - V shaped defect in frontal bones
Mass projects directly into soft tissues
Cribiform plate, Nasal bones & Orbits not displaced
other CNS anomalies more likely
6. Atretic Cephaloceles - Subcutaneous ectopic CNS tissue
assoc w cerbrooculomuscular Walker-Warburg syndrome
Glioma can form in ectopic tissue, glabella #1 site
DDx from dermoid cyst or sinus pericranii (venous blood)
Sinus Pericranii does not occur in midline

Nasal Glioma - ectopic glial tissue at root of nose at birth
30% intranasal, usually midline med to middle turbinate
60% extranasal, never midline
CT - isodense, rare calc, cannot DDx cephalocele
No CSF spaces like usual cephalocele
pedicle connection to brain in 15%
continuum of Dz w cephalocele, NOT a neoplasm
DDx - inflammatory polyp, inf lat to mid turbinate, >5y/o

7. Nasal Dermal Sinus & Cyst - ectoderm trapped by tube closure
Diverticula persists w attachment to ectoderm
Dermoid Cyst develops at the foramen cecum (ant to crista galli)
May become infected, drain from sinus to glabella
60% of nasal dermoids confined to the skin, 10% to cribiform
Nasal Dermal Sinuses resected due to infection & meningitis
No assoc w squa cell ca
Widened f. cecum & split crista galli poss w/o intracranial extention
Fibrous cord may extend thru w no Sx
patent sinus or dermoid elements indicate intracranial resection

DISORDERS OF DIVERTICULATION & CLEAVAGE
Ventral Induction - 5-10wks

HOLOPROSENCEPHALIES
complete or partial failure of cerebrum to divide
failure of lat cleavage into hemispheres
failure of transverse cleavage into dienceph & telenceph
this is all done at about the 5th wk
origin w same prechordal mesoderm which forms face
all have pachygyri

1. Alobar Holoprosencephaly - most severe, no cleavage
primitive horseshoe monoventricle, fused thalami
severe craniofacial anomalies, no septum pellucidum
NO interhemispheric fissure or falx
polydactyly, renal dysplasia, omphalocele & hydrops also
DDx - Hydrancephaly, vasc accident involving bi carotid
only thalami remain but N facies, N falx & N septum pellucidum

2. Semilobar Holoprosencephaly - intermediate severity
H shaped monoventricle, partial occipital & temp horns
incomplete fissure & rudimentery falx, fused basal gang
facial anomalies absent or mild, hypotelorism or cleft

3. Lobar Holoprosencephaly - nearly complete brain cleavage
Septum Pellucidum absent creating boxlike frontal horns
all but most ant falx, azygous ant cerebral art poss
Rare variant has fused central portion of fissure
assoc w neuronal migration abn & Callosal dysgenesis
Hypotelorism poss but rare, hypoplastic optic vesicles

4. Septooptic Dysplasia - De Morseir Syndrome, mild lobar
Absent sep pellucidum w squared frontal horns
Optic nerve hypoplasia, 50% assoc w schizencephaly
Thin Corpus Callosum

5. Arhinenecephaly - olfactory bulbs & tracts absent
holoprosencephalies include this, other syn as well
CORPUS CALLOSUM ANOMALIES
forms ant to post except rosturm last

1. Corpus Callosum Agenesis - occurs from insult at 18-20wks
Cingulate gyrus & sulcus also absent
Gyri form spokes extending out from a lg high 3rd vent
Probst bundles - longitudinal white tracts along lat ven
occur because unable to travel transversally
Lat Ventricles widely spread, pointed frontal horns
Colopocephaly - dilated occipital horns common

2. Partial agenesis - rostrum & splenium always absent
body & genu variable

3. Assoc Abnormalities - 60% assoc w other abn
Schizencephaly, interhemispheric cysts, heterotopias
Skeletal & midline facial anomalies
Cardiac, GI & GU anomalies also

4. Corpus Callosum Lipoma - assoc w 10% of callosal agenesis
fat incorporated into neural tube at 3-5wks
30% of intracranial lipomas occur here
50% assoc w various degrees of dysgenisis
Tubulonodular type seen w forebrain & rostral anomalies
may see lg vessels thru the more bulky ones
Ribbonlike curvilinear lipoma seen post, more often w N

POSTERIOR FOSSA MALFORMATIONS AND CYSTS

DANDY-WALKER COMPLEX
Cystic dilation of 4th vent, Vermian hypo or aplasia
Upward displacement of lat sinuses, torcula & tent

1. Dandy-Walker Malformation - etiology uncertain
Outflow Obstruction - atresia of Magendie & Lushka
possible cause of insult to Cb
post fossa enlarged by cyst which also displaces veins
Vermian Agenesis - 25%, remenant rotated sup to cyst
cb hemispheres have varying hypoplasia, ant lat disp
Obs Hydrocephalus - 80%, other CNS abn seen in 70%
hypoplastic brainstem, heterotopias, cephaloceles
Agenesis of Corpus Callosum assoc in 25%
if present also see colopocephaly
PICA hypoplastic, blood supply from AICA
Polydactyly & cardiac anomalies also assoc

2. Dandy-Walker Variant - mild vermian agenesis
"Key-hole" communication between 4th vent & cisterna mag
N size post fossa, N brainstem, hydroceph possible


OTHER CAUSES OF POST FOSSA CYSTS
must R/O cerebellar atrophy

1. Mega Cisterna Magna - N cb & 4th vent, lg post fossa
cisterna extends around & over vermis
prominent occipital scalloping may be noted
communicated openly w lumbar subarachnoid space

2. Post Fossa Arachnoid Cyst - CSF enclosed in split arach
Normally formed but displaced 4th vent & cb
can cause hydrocephalus which is never seen w lg cisterna magna
No comm to lumbar subarachnoid space
Retrocerebellar most common post fossa location, CP angle #2
can extend thru tentorial notch as can epidermoids


CEREBELLAR HYPOPLASIA'S & DYSPLASIAS

1. Cerebellar Atrophy - most II' to alchoholism, vermis disproportionally so
Shy-Drager Dz - autonomic sys dysfxn, occurs in middle age
temperature, sweat regulation & BP control abn assoc
Freidreich's Ataxia - auto dom presenting in 2nd decade
late childhood w lower ext ataxia most common
signal intensity N, dec AP diameter, cervicomedullary jxn atrophy
Down's, fragile X syn, Olivopontocerebellar degen, dilantin etc

2. Chiari IV Malformation - sever cerebellar hypoplasia, rare
sm brainstem & large post fossa CSF space assoc
Hydocephalus & other anomalies rarly seen in assoc

3. Jouberts Syndrome - Auto rec, split & disorganized vermis
inf & sup cb peduncles small, 4th vent superiorly convex
assoc w collosal dysgen, retinal dystrophy & occulomotor
also polydactyly, cystic kidneys & pulm disorders

4. Rhombencephalosynapsis - rare, vermian agenesis
Midline fusion of cb peduncles, dentate & colliculi
Assoc ventriculomegaly common as well as mult other abn

5. Tectocerebellar Dysraphia - rare, vermian hypoplasia
Occipital cephalocele & dorsal traction of brainstem
cb hemispheres rotated & lie ventrolat to brainstem

6. Lhermitte-Duclos Disease - Dysplastic Gangliocytoma of cb
hypertrophied granular cell neurons & axonal hypermyelin
gross thickening of cb folia w freq mass effect
hydroceph & calc poss, sim post fossa malig

SULCATION & CELLULAR MIGRATION DEFECTS
Migration - 2-5mo, nuerons follow radial glial fibers

1. Lissencephaly - absent or poor sulcation
colpocephaly, thickened cortex w smooth gray-white line
shallow sylvian fissure gives a figure 8 app on CT
may see calc in parenchyma if II' to intrauterine infec
Hypomylination & poor corticomedullary demarcation poss
Cerebrocerebellar type - hypoplastic cb & stem, no fig 8
assoc w Miller-Dieker, Walker-Warburg & musc dystrophy

2. Nonlissencephalic Cortical Dysplasias
Pachygyria - focal areas of flattened, thickened cortex
sulci >1cm in width

Polymicrogyria - diffusly thickend cortex, bumpy gyri
diff to distinguish the two by MRI, Histo for DDx
25% have underlying white matter abn, usually gliosis
Assoc w mult heterotopia's

3. Heterotopias - N neurons in abn place, 3 types
Laminar - Band Heterotopia, diffuse arrest, bands of alt gray & white

Nodular - mult subependymal collections of gray matter
can sim tuberous sclerosis but no calc, no enhance

Focal - isolated island of gray, often w schizencephaly
may protrude into vent, lg draining V if more periph
can have part or all of a hemisphere involved, no vent
may sim a gangliocytoma on bx

4. Schizencephaly - gray lined cleft to ependyma, 80% bilat
type I - closed-lip w walls closely apposed
type II- open lip w walls seperated, 80%
heterotopic gray lining more apparent, CSF in cleft
NO vasc thrombosis or glial scar in the seam
ependymal lining fused to pia at outer edge, covers cleft
may see a nipple of tissue at ependymal surface
DDx includes porencephalic cyst - P trauma, glial lining

5. Unilateral Megaloencephaly - hamartomatous overgrowth
involves all or part of one hemisphere
assoc w localized neuronal migration & white mat abn
ipsilat ventricle enlarged w freq midline shift

DISORDERS OF HISTOGENESIS: NEUROCUTANEOUS SYNDROMES
Neuronal prolif, differentiation & histogenesis - 2-5mo

1. Neurofibromatosis
Von Recklinghousen Dz - Type I, 90% of all cases, auto dom
Long arm of chrom 17 w 50% spontaneous mutation
60% have lesions of cord, dura, nerve roots or vert
Dx if two or more of the following is present
6 or more cafe-au-lait spots, I' relative w NF-1
2 or more neurofibromas or 1 plexiform neurofibroma
2 or more lisch nodules, pigmented iris hamartomas
Axillary or Inguinal freckles, Optic nerve Glioma
presence of a characteristic bone lesion
pseudoarthrosis, sphenoid dysplasia, unilat ant dist bow
Hamartomas - CNS deep WM & Cord, occur in 20%
4x more likely to develop neoplasm, esp optic N glioma
plexiform neurofibroma - mult worm-like masses along N
freq along trigeminal I branch
Neurofibromas - usually isointense w muscle, benign
90% of white matter lesions show no mass effect
basal ganglia lesions hyperintense on T1 & T2
Dural Ecatasia - Scalloping of post vert body II' to dural dysplasia
can cause int auditory canal enlargment
enlarged foramen II' to root neurofibroma, dumbbell
Kyphoscoliosis & meningoceles, esp in thoracic vert
mult aracnoid cysts can protrude along roots
cord lesions are typically low grade astrocytomas
Pulsitile Exophthalmos - sphenoid errosion allows temp lobe hern
Vascular Anomalies - esp in renal & GI, CNS rare
progressive cerebral art occlusive Dz & aneurysms
Renal art stenosis leads to hypertention, renal art aneurysms also
Tumors - meningioma, optic chiasm glioma & pheochromocytoma, rare

Neurofibromatosis Type II - bilat acoustic schwannomas
auto dom w defect in chrom 22, much less common than NF1
assoc w tumors of cranial nerves and meninges
trigeminal 2nd most affected, 2 or more on any CN = NF2
nonneoplastic choroid plexus & cb calc also seen
spinal cord & nerve root lesions very common
ependymomas also assoc w NF2

Segmental Neurofibromatosis - rare, genetically distinct
cutaneous & neural changes confined to one area of body
pain & puritus II' to mast cells in neurofibromas
2. Bourneville Dz (TS) - hamartomatous growths in mult organs
auto dom w high penetrance, variable expressivity
classic triad seen in 50% - Zits, Fits & Nitwits
4 major CNS manifestations poss II' to migration anomali
1) Cortical Tubers - 95% of TS pts, 20% cause local distortion
hypointense to WM on T1, hyper on T2, only malig enhance
rare malig deg, calc inc w age, 50% have calc by 10y/o
2) White Matter Lesions - can have four distinct patterns
bands extending from vent to cortex, wedge lesions
conglomerate foci & cerebellar radial bands
sim signal to tubers, unmyelinated infants opposite
3) Subependymal Nodules - 95% of pts, irreg bumps in lat v
60% near caudate in striothalamic groove behind monro
freq calc makes T2 hypo, still hyper on T1 in infants
4) Subependymal Giant Cell Astrocytomas - 15% of TS pts
all are at or near the foramen of monro, hydroceph
heterogeneous w freq calc, intense enhance, benign
Extraneural manifestations
Retinal Hamartomas - 50% of pts, rarly effect sight
Vascular Dysplasias - lg vessel ectasia & aneurysms
craniocervical vessel occlusion, moyamoya collateral
Facial angiofibromas, Shagreen Patches & papular nevus
Renal cysts & angiomyolipomas in 80%
Rhabdomyoma of myocardium, liver leiomyomas & adenomas
pulm cystic lymphangomyoma & fibrosis
Bone islands, cysts & thick periosteal new bone in 50%

3. Sturge-Weber Syndrome - Encephalo-trigeminal Angiomatosis
Capillary Venous Angioma, I' neuro lesion
Parietal & occipital meninges most commonly involved
venous stasis causes cortical atrophy & dystropic calc
ipsilateral HEMIATROPHY results
seizures, dementia, hemeplegia, hemianopsia & glaucoma
Tram Trac calc of gyri - occur in underlying gliosis by 2y/o
ipsilat calverial thickening, sinus & mastoid enlarg
Angiomatos vessels enhance as well as cortex & choroid
may see prom medullary & subependymal veins
Skull Thickening on effected side, II' to subdurals assoc w atrophy
Congenital Glaucoma & Choroidal Angiomata in 30%
Port Wine Nevus in trigem I distribution
Sporadic occurance, no genetic base
Hemiatrophy DDx - any insult to brain, hem most freq at present
thickening of calveria, overdeveloped sinuses & elev petrous bone
Dyke-Davioff-Mason Syn - atrophy of one hemisphere
Skull thickens, unilat dec in cranial fossa size, Seizure, MR
present in adolescence, no assoc calc

4. Von Hippel-Lindau Syndrome - mult hemangioblastomas of CNS
auto dom w incomplete penetrance & variable expresion
short arm of chrom 3, Rarely manifests before puberty
Hemangioblastomas - 80% brain & cord, by age 30
90% occur in post fossa, mult in 10% is pathog
isointense mural nodule w strong enhance, lg assoc v
Viceral Cysts & Neoplasms - 50%, renal cell ca by 40
75% have mult renal cortical cysts, Pheochromocytoma 10%
Retinal Angioma - 50%, manifest by age 20
dilated feeding art & draining V, often mult & bilat

5. Ataxia-Telangictasia - ataxia begins in childhood
marked progressive cb atrophy esp in ant vermis
Telangictasia seen late, familial syn, unknown origin
Inc incidence of malig, inc susceptability to pulmonary infection

6. Osler-Weber-Rendu - hereditary hemorrhagic telangictasia
Capillary Telangictasia primarily in skin & mucosa
A-V malformations & fistulae cause 50% of neuro complications
paradoxical thrombi, gas & septic emboli thrombos vessels
liver 30%, lungs 20% & spine 8%, Epistaxis in 85%
Aneurysms involving any size vessel

7. Neurocutaneous Melanosis - mult congenital pigmented nevi
leptomeningeal prolif of melanin cells, strongly enhance
40% develop I' CNS melanoma

8. Cowden Disease - Rare hereditary mult hamartoma syndrome
Skin & mucous mem lesions common
Neurofibromas, Meningiomas & neuromas also noted
Thyroid, breast, colon & adenexal cysts poss

HYDROCEPHALUS
Ventricles normaly hold 10-20% of CSF vol

1. Aqueductal Stenosis - occurs at level of sup collicule, <.2mm
#1 cause of congenital hydrocephalus (40%), 2:1 male
50% postinflammatory - TORCH or intracranial hem, present young
Developmental - caused by branchhing of aqueduct into channels
septum can also occur, 25% assoc w x-linked recessive
Neoplastic - very rare, pinealoma, meningioma, etc

2. Communicating Hydrocephalus - II' to obs beyond 4th vent
SAH #1 cause, meningeal carcinomatosis, infection
Achondroplasia, Hurler Syn, Superior Sag Sinus thrombosis

3. Normal Pressure Hydrocephalus - Dementia, ataxia & incontinence
form of comm hydroceph w incomplete obs of granulations
Pressure gradient exists between vents & parenchym, Shunt helps

4. Choroid Plexus Papilloma - causes overproduction hydrocephalus

5. Pseudotumor Cerebri - Benign Intracranial Hypertention
Inc pressure in ventricles due to increased subarachnoid volume
actually causes small ventricles in young obese middle age women
Elevated blood vol and/or decreased absorbtion
Venous occlusion from sinus or SVC thrombosis
Dural AVM, Hypervitaminosis A or Hypocalcemia

GLIAL ORIGIN TUMORS
Originate in deep White Matter, ALL are unencapsulated
Use WM for scafolding to spread
Hematogenous Dissemination only P surgical manip
#1 in children (infratentorial) & #1 primary in adults
gradations of tumor based on cellularity, pleomorphism
vascular proliferation & necrosis
Low grade can progess to high, often mixed
Fibrillary - diffuse & eventually fatal if untreated
Spread Under pial & ependymal layer, do not protrude
20% Calc, 5% hemorrhage
Circumscribed - rarely become malig
Pilocytic - low grade, noninfiltrating, freq cystic
Juxtatumoral fluid collection typical
interturmor cyst poss, sim GMF (NO occurance in kids)
Edema can be minimal, much less than mets in general

1. Astrocytoma - low grade but still fibrillary, "Benign"
rare, mostly kids & young adults, present as seizure
CT - NO Neovascularity so NO enhancement
Minimal edema, minimal mass effect, 15% calc
Low density periphery due to abn cells NOT edema
MRI - can have sharp margination despite no capsule
occasional mild Gd enhancement
will eventually transform to Glioblastoma multiforme
Cystic degeneration does occur, NO nec, NO hemorrhage

Gliomatosis Cerebri - diffuse spread of N astrocytes
Follow WM scaffolding thruout brain, just too many
Pt presents w diffuse hemispheric enlargement

2. Anaplastic Astrocytoma - High grade along w Multiforme
1/3 of fibrillary astrocytomas
Neovascularity & AV shunting poss, calc rare
Lack of central Necrosis seperates it from Multiforme
also called Gemistocytic - means bloated
Protoplasmic Astrocytoma - same, weblike stellate cells
DDx - Venous Infarct, can have gyriform enhancement
3. Glioblastoma Multiforme - 50% of fibrillary astrocytomas
Occur in older pt deep cerebral white matter, rare <30
CT - extensive edema due to breakdown of BBB in neovasc
Central necrosis, mass effect, calc rare, occ hem
May present multifocal, sim mets, subarachnoid spread
Rostrum of Corpus Callosum #1, crosses midline
MRI - irreg marg, Irreg enhancement, Dec T1, Inc T2
May be thicker & grow faster on Gray matter side
Angio - extensive Neovascularity, intense tumor blush
Abn draining vien w cent portion unenhanced freq
DDx - Lymphoma, but only has necrosis in AIDS pts

4. Gliosarcoma - Rare, glial & spindle cell mix, vasc origin?
lobulated w cent nec, sarcoma portion sharply defined
occurs in <2% of GBM, survival similar, freq dist met
more peripheral w dural invasion unlike GBM


5. Pilocytic Astrocytoma - bilologically distinct subtype
usually around hypothalmus, 3rd & 4th vent also
1/3 of pediatric astrocytomas, usually post fossa
distinct from brainstem gliomas which infil & kill
85-100% 5yr survival
oval & sharply demarcated, avasc on Angio
NO BBB, may homogeneously enhance despite low grade nature
Early hydroceph in 90%, usually cystic & large, no nec
Juxtatumoral Fluid typical manifestation of Cysts
"Cyst & Mural nodule" - enhances but no "blush" seen on angio
Synonymus w Juv Pilocytic Astrocytoma & Polar Spongioblastoma DDx - brainstem glioma, present w CN deficits, less hydrocephalus

Cerebellar Astrocytomas - May calc, but no hem
Hypothalamic Glioma - relatively benign course
1/3 assoc w Neurofibromatosis

6. Brainstem Glioma - 15% of kid braintumors, also in adults
diffusely infiltating, variable enhancement, nonpilocytic
usually in pons w post disp of 4th vent
MRI much more sensitive, occ calc & hem
Present w cranial nerve deficits, less hydroceph than pilocytic
7. Pleomorphic Xanthoastrocytoma - Rare, kids & young adults
Benign w extention to outer cortex & meninges
Cystic w discrete enhancing nodule, avasc, calc rare
pleomorphic lipid laden xanthomatous astrocytes
no nec, abundant reticulin network
Always Supratentorial, Solitary & present w Seizures
CT - shows enhancement of capsule & assoc meninge "tail"

8. Giant Cell Astrocytoma - Juxtaventric, subependymal calc
Arise from astrocytic giant cells in Tuberous Sclerosis
circumscribed, can cause hydroceph if at monroe foramen
Pedunculated & project into vent, freq calc

9. Oligodendroglioma - 5% of adult I', usually w glioma mix
from Centrum Semiovale #1, may extend to cortex & dura
May cause smooth errosions of inner skull
Very slow growing, 90% Calc w globular & "dot-dash" type
well circ, no capsule, minimal contrast enhancement
Pure oligos -freq cystic deg, no nec, avasc, rare hem
CT for calc, MR for tumor extent

10. Ependymoma - several histo types, cellular #1
Rule of 70's - 70% male, 70% 4th vent, 70% childhood
70% of intramedullary spinal cord masses
Variable malignancy - 50% 5yr surv, local recur, Can seed CSF
6% of neuro tumors, usually kids & young adults
Hydrocephalus - 100%, exude a protien which obs granulations
overproduction of CSF also plays a factor
lobulated, 50% w sm punctate calc, variable vasc, isolated 90%
Originate from floor of 4th vent, hetero enhancement
"plastic" - flow thru magendie & luschka
mixed cystic & solid, can nec, rare hem, ISO ON CT
supratentorial sim glioma, mostly older pt

Subependymoma - benign, solid nodule extending into vent
histo between astrocytoma & ependymoma
occur in elderly, usually asym, hydroceph if 40-60y/o

Ependymoblastoma - PNET variant of ependymoma

Myxopapillary Ependymoma - low grade solitary of cord
most around phylum terminale & cauda equina
11. Choroid Plexus Papilloma - from epi of choroid
Trigone of lat vent in 1st decade, 4th vent w adolescent
Frondlike margination, hypervasc w marked enhance
isointense on MR w mottling due to trapped CSF
Hem freq, blocks granulations, hydroceph even w/o obs
benign, but local recur common, rare invasion or mets
Also overproduces CSF
Choroid Plexus Carcinoma - very rare, more invasive
always in lat vents, all in infants 2-4 y/o
US - can be Dx in utereo, enlarged head
echogenic lobulated mass

NEURONAL TUMORS

1. Ganglion Cell Tumors - spectrum from well to poorly diff
Gangliocytoma - most differentiated, Neuroblastoma least
neuronal tumor w no neoplastic change
probably represents dysplatic hamartomas of brain

Ganglioglioma - rare benign tumor, 80% < 30y/o
contain both mature ganglions & supporting glial cells
Ganglioneuroma - pure ganglionic tumor, sim findings
Cyst w calc mural nodule common, slow growing
variable density & enhancement, can errode calvarium
Temporal lobes #1, NO distinguishing features on imaging

Desmoplastic infantile ganglioglioma - ganglioma subtype
rare, infants only, lg cystic mass in frontal lobes
meningial based nodule w extreme desmoplastic rxn
Enhancement of Solid portion & affected meninges

2. Lhermitte-Duclos disease - dysplastic cb gangliocytoma
progressive hypertrophy of cb folia, not a neoplasm
abn population of lg neurons found in inner layer of cb
abn mylenation of outer layer, prob malform not true Ca
migrational disorder vs Hamartomatous growth
MRI - gives characteristic striated appearance
CT - not helpful except that the mass Does NOT enhance
All other post fossa masses enhance, infarct homogen

Cowden Dz - mult hamartoma syn, Auto dom
GU & GI cysts, Ca & polyps, CNS meningiomas, Cataracts
Lhermitte-Duclos sometimes assoc but NO inheritance pat
3. Dysembryoplastic Neuroepithilial Tumor - Benign, temporal
Always present w partial complex Seizures
Glioneuronal nodules, assoc w cortical dysplasia
Calvarial errosion due to slow growth, NO enhancement
Sorlitary Wedge shaped enlargement of gyri, do not recur
NO edema or mass eff
DDx - Tuber, usually mult, spare outer most cortical lay

4. Central Neurocytoma - benign, rare, usually in lat vent
lobulated intravent mass adj to monro or septum pelluc
avasc w moderate inhomogeneous enhancement, mult cysts
Hydroceph & globular calc always

5. Tuber Cinereum Hamartoma - pedunculated mass ant to mam
can cause precocious puberty, "Laughing Siezures"
Well defined, project ant to pons, NO enhancement
Benign w no malig potential
Sim hypothalmic Glioma if large & sessile

6. Glomus Jugulare Tumor - origin from paraganglionic cells of jugular
follow formen to eustachian tube & nasopharynx, 10% bilat
invade petrous apex or internal carotid to middle cranial fossa
Middle age F>M by 3:1, pulsitle tinnitis, otorrhea & facial pain
palsy of CN IX, X & XI
External carotid supply - ascending pharyngeal art #1

Glomus Tympanicum - arises near cochlear promontory
CT shows mass due to bony erosion & enhancement

MENINGEAL & MESENCHYMAL TUMORS

1. Meningioma - #1 nonglial, 15% of all, originate from arachnoid cells
95% benign, 5% atypical, 1% anaplastic or malig, 90% Asym
15% of neuro tumors, usually older pt, female > male
90% extraxial, supratent, Sag Sinus at granulations #1
Sella - 20%, encase carotid, migrate post over tentorium
supplied by meningeal branches of cavernous carotid
often encases the cavernous carotid
Intraventricular - #1 mass in atrium of lat vents, no CSF prod or seeding
may "encyst" a temporal horn due to obstruction
NF-2 predisposes to meningiomas
assoc w mult & peds occurance, chromosome 22 specific
Radiation is also a predesposing factor
CT - Homogeneous & Dense, strong enhance but 15% inhomogeneous
Extensive edema possible in adj WM & immediate periphery
Minimal hem & nec in <5%, calc 25%, diffuse psammomatous
hem & nec do not distinguish malig from benign
very vasc, dural for center, cerebral for periph
Sclerosis of adjacent bone, good for DDx from aneurysm
Errosion of inner skull poss, rare at sella & base
90% can be Dx by CT alone, dural contact most helpful
MRI - may be inconspicuous w/o contrast
malignant type assoc w draining vien, hetero, etc
Dec T1, variable T2, freq sunburst pattern of vessels
Dural tail - infiltrates local dura, reactive changes
finding assoc w any process abuting meninges
malig most likely to recur, not predicted by imaging

2. Hemangioblastoma - Benign Auto Dom vasc neoplasm, unkown origin
60% cystic w a solid mural nodule, most well circ, rare hem or nec
hypervasc mural nodule abuts pia surface, strong enhance freq
nodule usually hypointense w prom serpentines on MR
Calc is NOT seen, Astrocytoma more likely if present
80% found in Adult Cb, #1 I' post fossa mass in an adult
Angio better than CT for Dx - nodule neovascularity evident
Von Hippel-Lindau Syn - assoc w 20%, occur at mid age
multiple nodules diagnostic, 10%
20% secrete erythropoietin - cause polycythemia

3. Hemangiopericytoma - arise from pericytes in capillaries
rare, lobulated & well circ, occur in middle age
freq local recur & met esp to bone & lung
vascular & heterogeneous pre & post contrast
4. Mesenchymal tumors other than meningioma - rare
Benign - ossified dura, falx osteoma or enchondroma
Meningial melanocytoma - rare, extraaxial, sim meningioma
benign course, usually in post fossa or canal
I' malig leptmeningeal melanoma much worse, diffuse pres
Malig - dural chondro, fibro, or angiosarcomas

PINEAL GERM CELL TUMORS
in any pineal mass check cord for drop mets
Pinealoma - general term for all germ cell tumors here
Parinauds Syndrome - may present as paralysis of upward gaze
Any calc >1cm should be considered suspicious
ring calc can be due to incidental calcified cyst

1. Germinoma - 60% of germ cells & 40% of pineal neoplasms
always occur near midline, II' implants in ant 3rd vent
can have diffuse ependymal & subarach spread
unencapsulated, surround calc pineal, invade adj thal
Hyperdense w strong contrast enhancement, + placental alk phos
isointense on MR pulse sequences, use contrast for mets

2. Teratoma - #2, 15% of pineal masses, male predominance
multipotential cells that recapitulate N organogenesis
heterogeneous w calc, cystic & lipid portions

3. Choriocarcionoma - <5% of pineal masses
extraembryonic placenta like cells, elev bHCG levels
cannot be distinguished from other germ cell on images

4. Endodermal Sinus Tumor - "yolk sac" tumor, mixed histo
Elev serum alpha-fetoprotien, no distinction on images

5. Embryonal Cell Ca - lg undif embryonal epithelial cells
alpha-fetoprot & bHCG elev, no distinction on images

6. Pineal Cell Tumors - <15% of all pineal tumors, middle age
Pineocytoma - benign from parenchymal cells
sm one can sim a benign pineal cyst
assoc w dense calcification
Pineoblastoma - malig, undif pineal cells, calc rare
actually a primitive neuroectodermal tumor
heterogeneous w strong enhancement, no capsule

NONNEOPLASTIC TUMORLIKE LESIONS

1. Epidermoid Tumor - nonneoplastic inclusion cysts
cuboid lining which continues to desquamate
congenital - trapping of dermal epi during tube closure
Does not present until 30-40yrs due to slow expansion
aquired - implantation of epi from trauma, ie spinal tap
40% in cerebelopontine angle, most intradural
most common scalp lesion in children
well delineated cysts w lobulated margins, no enhance
avasc, 25% calc, hem can make them appear hyperdense
CT - very low density, sim to CSF, Rarely DDX from Arach Cyst
can be hyperintense on T1 due to high lipid
does not resemble the water density of arachnoid cyst
"flaccid" ballon app vs "tense" ballon of arach cyst

2. Dermoid Tumor - ectoderm & mesoderm inclusion cyst, rare
Dense fibrous capsule, rarely enhance or calcify
includes hair & sebaceous glands
high lipid content, rare calc may include dental
avasc, may induce vasospasm, hyperintense on T1
MRI - heterogeneous on T2, best way to DDx from arach cyst
may see fat droplets in subarach due to rupture
Occur near midline, lumbosacral canal #1, parasellar #2
4th vent & vermis often, ruptures cause menin inflam
inc size due to desquam & gland excretion, benign
Rupture causes fat-fluid levels in vents but NO meningial enhancement
does cause hydrocephalus but does not implant & spread

3. Lipoma - a choristoma, N tissue in the wrong place
not a hamartoma or neoplasm, a maldifferentiation
Rare, not assoc w age or gender, 80% midline near corpus
Present w seizure, envelope CN, resection diff
Tubulonodular Lipoma - lg bulky & cylindrical
assoc w corpus cal agenesis & cephaloceles
Curvilinear Lipomas - thin post lesions seen at splenium
no corpus callosum dysgenesis
Calc & prom vessels coarse within but avasc in general
infant lipomas seen on US assoc w corpus anomalies
very low density(-50 to -100), no enhancement
fat intensity, hyper T1, hypo T2, use fat suppresion
NONNEOPLASTIC CYSTS
no neoplastic transformation

1. Arachnoid Cysts - congenital, CSF within arachnoid
1% of CNS masses, wall of cuboidal arachnoid, no epi
any size, brain comp can be severe, temporal dysgen freq
50% middle cranial fossa, 10% cerebellopontine angle
Most are retrocerebellar in post fossa, cause Hydrocephalus
Occur at all ages, 75% in children, M:F 3:1
80% symptomatic, most do not grow, larger more likely
Smooth demarcation, no calc, no enhancement unless hem
displaces brain, errodes calvarium, CSF intensity
can sim dermoid, open lip schizencephaly or infarct
Dandy-Walker Malform & dilated 3rd vent diff to DDx
DWM is extention of 4th vent, hypoplastic vermis
DDx at CPA - Epidermoid less intense, "flaccid" ballon
Large Cisterna Magna - will not cause hydrocephalus

2. Colloid Cyst - always in ant 3rd vent near monroe
intermittent hydroceph freq, sudden death from obs poss
Endodermal origin - bronchi or nasal epi, up to 4cm
filled w thick viscous fluid, enlarge w secretions
1% of CNS tumors, 20% on interventricular tumors
become symtomatic in 3rd decade, removal currative
CT - homogeneously hyperdense, 40-70HU
round & well marginated, NO enhancement
DDx - papiloma, aneurysm, meningioma or glioma
all enhance
MR - Bright on T1 & T2 realtive to brain, high protien

3. Rathke Cleft cyst - primitive stomodeal remenant
most purely intrasellar w occ suprasellar component
1-2cm w cuboidal lining & serous or mucinous fluid
1% of CNS masses, rarely symptomatic, usually adult
may present as visual or hypothal-pit dysfunction
Well marginated, low density w 50% capsular enhancement
No calc, usually hyperintense to T1 but variable
may see compressed pit gland around cyst
DDx - craniopharyngioma, pit adenoma, arachnoid cyst
4. Neuroepithlial cysts - choroid plexus or ependymal
midline w primitive neuroectodermal elements
50% of autopsies have a sm one, rarely symptomatic
lat vent plexus #1, hydroceph poss but mild
Well marginated, CSF density & intensity, no enhancement
No calc, spindle shaped on sagital exam

5. Enterogenous Cysts - rare, intraspinal 80%, intracranial
residual of neurenteric canal, endodermal elements
thin walled w serous or milky fluid
usually intradural, post fossa, variable presentation
Well marginated, no calc or enhancement, iso w CSF

SELLA LESIONS
Mets #1, freq site of mass like infection also
ant pit - adenohypophysis, connects to pituitary stalk
post pit - neurohypophysis, brighter on T1, DDx from clivus fat
stalk - may enhance w histiocytosis

1. Pituitary Adenoma - divided by size & original cell type
microadenoma - <10mm, 400X more common, asym, rarly seen
macro - >10mm, often extend sup to suprasellar cisterns
visualized twice as often as micro
slow growing, benign, <1% of adenomas transform
usually asym, but high recurrance when removed
isodense & isointense w N pit, delayed enhancement
N pituitary has a rapid intense enhancement
nec, hem or cysts may result in mixed density
Pituitary Apoplexy - bleed into mass, HA, vision changes etc

Prolactinoma - lat position in ant pituitary, 5:1 female, mild serum elev
25% of pit adenomas, get very lg in men w lg serum el
Bromocriptine causes rapid reduction in tumor mass

Growth hormone adenoma - also lat position
15% of adenomas, gigantism in kids, acromeg in adults
more likely to transfrom & invade superiorly

Null cell adenoma - secrets many nonfunctioning subunits
often present as macroadenomas, includes oncocytoma

Coricotrophic adenoma - midline, 10% of adenomas
secrete ACTH causing cushings dz even w very sm tumor

Gonadotrophic adenoma - diffusely distributed, FSH & LH
infertility & menstrual irreg in women, silent in men

Thyrotropic adenoma - midline, 1% of adenomas
secrete TSH causing hyperthyroidism

Plurihormaonal adenoma - 1%, secret TSH, prolac & growth
sx depend on dominant hormone

Choristoma - granular cell tumor of post pit, bright like post pit
enhance, may be very vascular
visual or endocrine disturbances may be assoc
2. Craniopharyngioma - squa epi from Rathke's duct remenant
5% of all intracranial tumors, #1 non-glial in kids
Benign histology, but grow relentlessly w/o intervention
Posterior Sellar #1, 75% combined w suprasellar component
lobulated cystic mass w a mural nodule
Central Coarse Calc seen in 75% peds, 50% of adults
rim calc rare, all in peds cases, fluid is high protien
Hem freq, intensity variable, resection difficult
freq growth into post fossa, esp cystic portion
Sx - visual change Rare due to post location & cystic nature
Endocrine abn #1, usually diabetes insipidus
DDx - Rathke cleft cyst, nec adenoma, aneurysm, glioma
Hypothalamic Glioma - rarely cystic, grows along CN III

3. Tuberculum Meningioma - cause sclerosis of adjacent sella
more anterior than pit tumors, displace circle of willis post
blood supply from post ethmoidal branch of ophthalmic artery

4. Empty Sella - arachnoid herniation into sella, pit gland compressed
most result from congenital weakness of diaphragm sella
hydrocephalus or other cause of inc intracranial pres, pseudotumor cerebri
most asymptomatic & normal endocrine
Shehan's Syndrome - pituitary apoplexy, can be expansile
usually II' to postpartum infarction of ant pit
also seen w massive hem into pit adenoma
occurs mostly in pts on bromocryptine
most have squashed remenant in floor, no clinical Sx

5. Congenital Cysts
Rathke's Cleft Cyst - Rathke's pouch remenant, ant sellar or suprasellar
cuboidal epi, ciliated or goblet cells poss, mucous filled
do NOT calcify
Epidermoid - can be isointense w CSF
can insinuate themselves around stem, difficult DDx
Dermoid, Teratoma & Lipoma - all have fat density
Arachnoid Cyst - 15% arise here, can be difficult to seperate from 3rd vent
assoc w optic Sx & may cause hydroceph

7. Aneurysm - angiography is required to give exact site & origin
cavernous hemangiomas may also be found in sella
many are parasellar in the cavernous sinus

8. Germinoma - arise from germ cells in suprasellar region
usually in children & young adults, may be locally invasive

PRIMITIVE NEUROECTODERMAL TUMORS (PNET)
undif tumors of children
contain components of neural & mesenchymal cells

1. Medulloepithelioma - most undifferentiated, occur early
present w enlarged head, lg heterogeneous mass
Hem, nec & cytic common

2. Medulloblastoma - infratentorial, 75% midline, 25% lat
origin from bipotential ebryonic cells of 4th roof, vermis
N cells form ext granular layer of cb, persist 1yr
rarly extend to cerebellopontine angle like ependymo
dense round cells, pear or heart shaped mass in vermis
homogeneously hyperdense w mod enhancement, vascular
Calc, Hem & cystic degen are RARE
fills 4th vent into magendie, obs hydroceph common
more variable in older children, 50% in cb hemispheres
CSF Mets - early & massive, occur in 50%
Zuckerguss - sugar coating app of LEPTOMENINGIAL METS
Distant Mets - to bone & marrow
Tx - extremely radiosensitive

3. I' Cerebral Neuroblastoma - also call supratentorial PNET
Rare, 80% in first 5 yrs, 18% of neoplasm in first 2 mo
CSF spread, check for drop mets, 30% 5yr survival
Lg sharply circ hemispheric mass of undiff cells
cluster in rosetts w nec, hem, calc & cysts
avasc, heterogeneous w mild enhancement
Ganglioneuroma & Gangliocytoma - related cell lines
progressively more mature forms

HEMOPOEITIC NEOPLASMS

1. Primary CNS Lymphoma - occur in compromised & N, all ages
Usually B-cell non-Hodgkins lymphoma, 20% multiple
often deep basal ganglia & perivent, abut ependyma
Highly radiosensitive, 100% initial remission, recur 1yr
Hyperdense w strong homogeneous enhancement
isointense to gray on T1, slightly hyper on T2
AIDS related can be heterogeneous w ext hem & nec
Lymphomatosis Cerebri - diffuse infil thru gray & white
sim Gliomatosis Cerebri

2. Primary CNS Leukemia - very rare, Granulocytic Sarcoma
assoc w systemic leukemia usually
Enhancing dural based mass, poss involve hypothalmus

CRANIAL & SPINAL NERVE TUMORS
1. Acoustic Schwannoma - benign periph neuroectodermal tumor
Well encapsulated round tumors, eccentric to nerve
ALWAYS arises in IAC, extends out like icecream cone
freq cystic or fatty deg, bone changes late
avasc, hypodense w rare hem or calc
Strong enhancement, hypointense on T1, hyper on T2
DDx - meningioma is more homogeneous, broad attach
10% of I' CNS tumors, 80% of CPA tumors
18% occur w neurofibromatosis 2, most pts older
CN VIII account for 95%, usually sup div of vestibular
sx of tinnitis & hearing loss more than disequilibri
facial parathesia #1 presenting sx
CT - enhancing, errosion of the crista falciformis
facial & trigeminal nerves also commonly involved
can form dumbbell w intra & extracranial portions
pure motor nerve involvement rare except w NF-2
bilat acoustic neuromas pathognomonic of NF-2
Angio - shows no tumor blush, good DDx from meningioma

Trigemninal Shwannomas also occur, <5% of schwanomas
Most extend along path of nerve from gasserian gang & post fossa
Cause unique enlargement of f. ovale & f. rotundum
Olfactory & Optic nerves have no myelin sheath

2. Plexiform Neurofibroma - unique to Von Recklinghausen, NF1
loose matrix of schwann cells, fibroblasts & reticulin
unencapsulated, diffuse infil of subQ tissue or nerve
Fusiform enlargement of mult nerve fascicles
no fatty or cystic deg, no hem, mod enhancement
expand foramina & erode bone
Isointense on T1, hyper on T2
Found at any age on peripheral or CN, 10% malig deg
ophthalmic branch of trigeminal #1
malig deg usually in peripheral or viceral Nerves


METASTATIC TUMORS
masifestations from hematogenous spread adenoca & breast

1. Skull Mets - breast & lung #1, CT best for bone component
MR best for delineating intradiploic lesions & ST extent

2. Dural Mets - less common than skull, often simultaneous
often simulate benign meningioma, but only unilat
Bilat involvement indicates a infil process like lymphoma etc
Pachymeningeal Carcinomatosis - rare intracranial process
Dura diffusely infiltrated, thick & nodular

3. Leptomeningeal Metastases - 20% of mets go to pia or arach
Arch/subarachnoid mets infil & thicken, nodules less com
basal cisterns #1, contrast MR best
CT - not seen unless hydroceph or oblit of cisterns, 30%
Communicating Hydroceph in Pt w known I' is suspect
Pial mets usually assoc w arach mets from extracranial
isolated pial spread assoc w high grade gliomas
can form a miliary pattern in perivasc dist
Ependymoma, Pineoblastoma & Medulloblastoma freq local ext
Carcinomatosis Encephalitis - diffuse to cortex & menin
Enhancement of basilar cisterns & bilat cranial nerves V & VII

4. Parenchymal Mets - #1 site for extracranial tumors
lung, breast & melanoma most common, GI & GU #4
25% of all adult brain tumors, 75% mult, 90% nec
Corticomedullary jxn #1, Median survival 3-6 mo
CT - iso to hyperdense, freq hem & sig local edema
Melanoma & Choriocarcinoma most likely to bleed
Strong enhancement, improve sensitivity w delay
isointense on T1, melanoma hyper due to high melanin
prolonged T2 relaxation (hyper), freq variable though
can sim N mult vasc lesions in elderly, no enhance
MR sensitivity inc w higher contrast dose, .2 mmol/kg
delay does not improve MR, cystic & calc only P Tx

5. Limbic Encephalitis - Paraneoplastic syndrome, sm cell #1
cancer causeing problems w/o occupying the organ
no gross pathologic or histologic changes
gyriform enhancement of temp lobes, insula & cingulate
Present w dec mental status & memory loss
CT usually N, sim viral encephalitis

INTRACRANIAL HEMORRHAGE EVOLUTION
1. Immediate - liquid w 95% O2 saturated Hg, T2 hyper, T1 iso
within seconds platelets thrombi form & cells aggregate

2. Hyperacute stage - 4-6 hrs, fluid serum begins to dispers
protein clot retracts, red cells become spherical, oxy
early peripheral edema begins, T2 iso, T1 iso
OxyHg is diamagnetic w no unpaired e-, no T1 or T2 eff
CT - isodense for 1-3hrs, then becomes dense, 60-100HU

3. Acute stage - 7-72 hrs, red cells begin to compact, deoxy
Central portion T2 hypo, T1 iso
DeoxyHg is paramagnetic w 4 unpaired e-, sig T2 shorten
sheilded from H2O by globin, prevents T1 shortening
no proton-electron relaxation enhancement can occur
Edema pronounced in periphery where T2 hyper
dense on CT, window width of 150-250 best

4. Subacute stage - 1-4 wks, methemoglobin starts day 4
begins at periphery & progresses towards anoxic center
cells begin to lyse at 1 wk releasing metHg, dec edema
perivascular inflam rxn begins w macrophage at periphery
Ring Enhancement caused by this process
T1 BRIGHT due to 5 unpaired e- exposed by globin change
proton-electron relaxation enhancement does occur
periphery affected 1st, middle remains iso initially
T2 HYPO early when methemoglobin still in RBC
BRIGHT once the cell breaks down & Hgb diluted in H2O
CT attenuation decreases approx 1.5HU per day
CT is NOT an accurate indicator of age, due to variable Hgb etc

5. Early Chronic stage - >4wks, edema & inflam rxn subside
vasc prolif encroaches on hematoma decreasing its size
dilute uniform pool of extracellular metHg w vasc walls
macrophage contain ferritin & hemosiderin at periph
T2 hypo due to strong magnetic susceptibility
T1 iso due to fact that hemosiderin is H2O insoluble
hypodense on CT unless rebleeding has occured
6. Late Chronic stage - cystic or collapsed w dense capsule
vasc prolif gradually forms fibrotic matrix w macrophage
infants may resolve completely
ferritin laden scar persists for years in adults
10% calc w residual hypodense focus in 40%

Gradient echo is helpful in detecting Hem in low field MRI's
See Blooming of signal void


OVERVIEW OF HEMORRHAGE ETIOLOGIES
see specific sections for more detailed discusion
underlying cause often hidden by the bleed
intraventricular extention assoc w 10% mortality

1. Neonatal Hemorrhage - germinal matrix hem II' to prematur
thin walled, proliferating vessels in subependyma of lat
caudothalamic groove
involution occurs at 34 wks when all cells have migrated
Never hem in utero or beyond first 28 days P birth
Grade I - Hem confined to germinal matrix, can be bi
Grade II - rupture into N size vent
Grade III - intravent hem w Hydrocephalus
Grade IV - extension to adj hemispheric white matter
Can be seen by US in acute & subacute, lucent if chronic
Term Infants - Hem usually II' to trauma, subdural #1
Asphyxia & infarction #1 in non-trauma
postlat lentiform nuc & vent thal most susceptable

2. Hypertention - #1 cause of nontrauma bleed in adult
Lenticulostriate & Pontine vasc #1, penetrating branches of MCA
Usually spontaneous in elderly pts, basal ganglia #1
Vessels often abn, Ruptured microanuerysm etc
50% have hem dissection into vents, poor prognosis
Lobar white mat hem in 20%, cb #1, midbrain & stem rare
originates along perf branches near dentate
Active bleeding usually lasts <1hr
Edema progresses for 24-48hrs, 25% die in this period

Hypertensive Encephalopathy - occurs II' to elev BP
Toxemia #1 - autoregulation overwhelmed esp in post
overdistention of arteriole leads to BBB breakdown
reversible vasogenic edema results, frank hem rare
Cortical petechia & subcortical hem poss, esp in occ
Inc T2 in ext capsule & basal gang more common
chronic renal Dz, TTP, & Hemolytic-Uremic syn also

3. Hemorrhagic Infarction
Arterial Infarction - hem when endothelium reperfused
occurs in 50%, but only seen in 10%, MRI>CT
Cortex & basal gang from MCA dist #1, 24-48hrs later
Pseudolaminar Cortical Necrosis - generalized hypoxia
middle layers usually eff, gyriform hem
nonhemorrhagic ischemic changes can occur, gyri calc
Venous Infarction - usually assoc w dural sinus throm
dura around sinus will enhance, clot stays hypodense
empty delta sign
more likely to effect white matter than cortex

4. Aneurysms - 90% of nontraumatic subarachnoid hem
#1 presenting sign for aneurysm, CT best for acute SAH
blood usually fills ambient cisterns & sylvian first
90% of blood cleared from CSF in 1wk
MRI better for subacute or chronic SAH, dirty CSF
Superficial siderosis - hemosiderin deposit on meninges
cb, stem & cranial nerves also coated - neuro dysfxn
Giant aneurysms >2.5cm often have intramural hem
most from carotid, cavernous portion #1, all ages
rarly bleed, Sx from local compression
75% have calc IF thrombosed, none otherwise
Charcot-Bushard Aneurysm - II' to Htn

5. Vascular Malformations - any can bleed
only AVM & Cavernous Angioma commonly
most bleed into parenchyma rather than subarachnoid
Arteriovenous Malformation - pial, dural or mixed, No cap bed
Pial AVM's - hem @ 2% per yr, often in prev N young pt
70% hem by 1st exam, repeated hem can sim neoplasm
Central nidus w gliosis & encephalomalacia
Dural AVM's - no central nidus, SAH or subdural
hem rare unless drainage thru cortical veins
Cavernous Angioma - hem @ .5% per yr, freq repeated bleeds
Popcorn like w mixed signal foci & hemosiderin ring
Venous Angiomas - Hem rare, sim hem of other malformations
medusa like collection of dilated medullary veins
Capillary Telangiectasias - usually sm & clinically silent
may see mult sm foci of hemosiderin on T2

6. Neoplasms - see specific sections

INTRACRANIAL ANEURYSMS & VASCULAR MALFORMATIONS
Charcot-Bushard Aneurysm - II' to Htn
20% mult, higher mult incidence in female esp if >2
Look for familial causes such as Polycystic Kid Dz

SACCULAR ANEURYSMS
berrylike outpouching from art bifurcation
include intima & adventitia, media ends w N vessel

1. Etiology - hemodynamic induced injury, abn shear forces #1
trauma, infection, tumor, drug abuse & AV malformations
Berry Aneurysms - assoc w polycystic kidney Dz & aortic coarctation

2. Incidence - 1% of angios & 5% of postmortems
mult in 20%, esp in females & polycystic kidney Dz
Bilat in 20%, esp at cavernous sinus, Pcom & MCA trifurcation
occur age 40-60 unless traumatic or mycotic, lg in child

3. Associated Conditions - occur at anomalous vessels & AVM
Inc pressure ie HTN & aortic coarctation
Systemic Dz - Marfans, fibromusc displasia, polycystic k

4. Location - 30% at ant comm, 30% at post comm, 20% MCA orig
10% in post circ esp basal art bifurc
traumatic or mycotic occur anywhere

5. Clinical Presentation - asym until rupture or giant >2.5cm
1-2% risk of rupture per year, 3.5% risk of surg
no diff risk w htn, age, sex or multiplicity
all should be repaired if >3yr life expectancy
Subarachnoid Hem - clinical grade by Hunt & Hess scale I-V
Vasospasm #1 cause of morbidity, 30% die
highest bleed rate in 1st 24hrs, 50% rebleed in 2wk
CT - shows SAH in >80% of ruptured aneurysms
cavernous sinus aneurysms can compress Nerves III-VI
TIA, Seizures & embolic ischemia less common

Giant Aneurysms - most from supraclinoid carotid, all ages
Fibrous vascular walls, rarely rupture, Sx II' to mass effect
Partially Thrombosed Aneurysms - 75% have curvilinear calc
CT most specific for these w target seen
NO calc if not thrombosed
DDx - Meningioma, both errode sella & lat sphenoid
aneurysm has no assoc hyperostosis or atherosclerosis
6. Appearance of Saccular Type - catheter angiography definitive
asses for relation to vessel, adj branches & vasospasm
essential in assesment of nontraumatic SAH
Thrombosed aneurysm will have no finding, 15%
may see mass effect if large
irregularity or local vasospasm can indicate rupture
DDx vascular loops & infundibuli (embryonic funnel <2mm)
CT may show bone erosion in long standing case
Patent aneurysms enhance intensely w contrast
Location of SAH can be prognostic indicator
ambeint cisterns ant to stem prob just vein rupture
no repeat angio needed
Suprasellar cistern to lat sylvian fissure
more aneurysmal pattern, must do F/U angio
MRI dependent on pattern of flow, turbulence & clot
may have wall enhancement w gd, laminated w thrombois

7. Traumatic Aneurysm - <1%, but occur in 50% of GSW
nonpenetrating usually occur at skull base, or shear
hyperextention stretches ICA over lat C1

8. Mycotic Aneurysms - II' to infection of art wall, rare <10%
adventitia & muscularis disrupted, thoracic aorta #1
Angio - occur dist to usual location, 2nd branch MCA #1
most common cause of mult MCA aneurysms
usually small, staph & strep most common, inc in child
bleed into parenchyma or SAH equal incidence
Abx tx has dec incidence, more common in immuncomprom
Medical Tx usually sufficient to control, surg if enlarge on angio
Mucor & Aspergilla invade direct from nasopharynx
cause thrombosis & infarct more often than aneurysm

9. Oncotic Aneurysms - usually extracranial, exsanguante freq
tumor may implant or cause emboli, I' or met

10. Flow-Related Aneurysms - seen w AVM's in 30%
distal ones most likely to hemmorhage

11. Vasculopathies - rare but seen w SLE, infarct & TIA #1
Takayasu's Arteritis - 9:1 female, inflammation & stenosis #1
prox arch vessels, L subclavian #1, often occludes
Fibromuscular Dysplasia - up to 50%, disection & A-V fis, 65% bilat
Cocaine - 50% w CNS sx have SAH, may be II' to HTN rx
several drugs cause vasculitis sim periarteritis nod

FUSIFORM ANUERYSMS
Etiology - atherosclerosis, exagerated arterial ectasia
media damaged, stretches & elongates, freq mural thromb
Vertebrobasilar Dolichoectasia - #1 site, older pt
often thrombos producing brainstem infarcts
can also compres local stem causing nerve palsies
Imaging - enhance if patent, hyperintense if thrombosed
curvilinear calc pathog, may cause skull base erosion

DISSECTING ANEURYSMS
Etiology - intramural blood from tear in intima
may narrow or occlude lumen, may distend subadventitia
do not confuse w Pseudoaneurysm, a encapsulated hematoma
Presentation - usually extracranial unless severe trauma
#1 in midcervical ICA & vertebral from C2 to skull base
Catheter angio remains procedure of choice for assesment

INTRACRANIAL VASCULAR MALFORMATIONS

1. Parenchymal AVM - congenital, dilated art & veins w/o cap bed
98% solitary, mult in Osler-Weber-Rendu & Wyburn-Mason
Incidence - 85% supratentorial, peak 20-40y/o, 25% kids
Hem in 85% w 3% per year risk, seizure 25%, deficit 25%
Size not predictive, deeper & smaller bleed more
Parenchymal #1, also #1 cause of SAH if <20yrs, less morbidity
Vascular Steal - atrophy due to vasculopathy of feeding vessel
atrophic low density regions & hem w high density
Overlying meninges thick & hemosiderin stained
Angio - shows massed feeding art & tortuous veins
often wedge shaped, poss to appear N if thrombosed
GBM may sim but usually has tissue between vessels
10% have aneurysms in feeding art, can bleed
Cryptic AVM's - not seen by angio, 10%
CT - often absent w/o contrast, 25% have min curvilinear calc
mixed inc & dec density if seen, Mild mass effect poss
Enlarge post venous sinuses but not cavernous sinus
Calc seen in <1/3, adjacent low density due to Atophy
MRI - honeycomb of flow voids, inc signal if thrombosed
hem in different stages often present
No significant interveneing brain tiss, DDx from GBM
TX - resection if unruptured, must be completely removed
Aneurysms must be Tx seperatly, inc risk for bleed
2. Dural AVM's & Fistulae - form within a venous sinus
no discrete nidus, mult microfistulae, occlud sinus freq
Follow recanulation of thrombosed sinus, 10% of all AVM's
Transverse or Sigmoid sinus #1, Bruits & headache #1 Sx
Cavernous sinus AVM - proptosis, retroorbital pain, proptosis
SAH common if reflux flow forced into cortical veins
Carotid-Cavernous fistula related, follow trauma
Occipital & Meningeal branch of ext carotid #1 feeders
CT often N, MRI may show dilated cortical veins

3. Mixed - 15%, if parenchymal AVM recruits art from dural supply

4. Capillary Telangiectasias - mult nests of dilated capillaries
#1 in pons & Cb, usually incidental on post but may hem
Gliosis of adj brain & hemosiderin staining from hem poss
Cavernous Angiomas assoc or simply the extreme form
Osler-Weber-Rendu - hereditary hemorrhagic telangictasia
25% have brain abn, most are true AVM's
Visceral angiodysplasia w scalp & mucous mem telangic
2nd most common lesion to venous angioma at autopsy
Not visualized by angio, may see w epistaxis
CT may faintly enhance, faint on MRI

5. Cavernous Angiomas - Hemangioma or cavernoma
circumscribed nodule of honeycomb sinusoidal vascular spaces
separated by fibrous bands but no intervening neural tissue
freq MULT HEM at diff stages, reticulated core of vessels
Supratentorial 80% but can occur anywhere, 50% mult
#1 vascular lesion identified, 20-40y/o
Siezure, deficits & HA most common presenting Sx
Angio does NOT visualize, poss faint blush in early venous
CT shows freq Calc, variable enhancement, can sim neoplasm
MRI - popcorn like appearance on T2 due to mult hem
mult areas of signal drop-out due to hemosiderin

VENOUS MALFORMATIONS
1. Venous Angioma - dil anomalous veins converge on cent vein
Etiology - remenant embryonic venous sys, usually solitary
assoc w migrational abn & cavernous angiomas in 30%
Sx - asym, Hem very rare unless from assoc cavernous angioma
CT - may show linear tuft of vessels post contrast
located in deep WM of cortex or Cb, #1 adj to frontal horn
MRI - shows stellate tributary veins into prom collector v
gliosis or Hem seen in only 15%
Angio - the only vasc malformation w a Single draining vein
Medusa head appearance on venous phase of angio

2. Vein of Galen Aneurysm - enlargment of galenic system
II' to arteriovenous fistulae from choroidal art
AVM in thalmus or midbrain can also cause this
Present at birth w high-out put heart failure, cranial bruit
Macroceph w obs hydroceph, deficits & ocular Sx
US shows bidirectional flow in vein of galen
Angio demonstrates either chorodal art or thalmoperf feeder
dilation to venous varix w or w/o dist stenosis
if stenosed distally will often thrombose
CT - lg enhancing midline mass post to 3rd vent
Hydrocephalus freq but rare hemorrhage
enhanceing serpentine vessels in thalamic region

3. Venous varix - assoc w several intracranial vascular abn
enlarge & thin resulting in SAH, hydroceph & increased ICP

Sinus Pericranii - venous hemangioma adhered to outer skull, deep to galea
supplied from intracranial sinus & blood returns to sinus
present w enlarging fluctuent ST mass, enlarge w crying
often II' to trauma, often resolved w prolonged compression
Frontal #1, parietal #2, most near sag sinus, can be very lat
Skull Film - usually sharp margins, vasc honeycombe poss
CT - shows strong uniform enhancement
MRI - well delineated ovoid or fusiform areas w variable signal

Venous Cavernoma - subcutaneous lesions of scalp
blood supply from ext carotid, drain to external jugular

4. Orbital Venous Varix - rare vasc malformation in orbit
Causes intermittent proptosis & diplopia w valsalva & bending over
Disappear completely w axial views, use tournequet on jugular vein

NEONATAL HEMORRAGE
Caudothalamic groove - between head of caudate & thalmus
both make up lat wall of lateral vent, terminates in monroe
Foramen of monroe - divides frontal & body portions of vent
thalmus entirely post, caudate head ant, choroid enters it

1. Subependymal Hemorrhage - preterm infants <32wks
Correlates w size of germinal matrix at birth, largest 24-32wks
involutes & is absent by 40wks, last in inf lat wall of frontal
lies inf to ependyma, sup to head of caudate & ant to thalmus
Usually occurs in first 3 days, always by 7-8 days
Grade 0 - N, Grade I - subependymal alone
Grade II - intraventricular w no ventriculomegaly
Grade III - Hydroceph, Grade IV - intraparenchymal
grade does not predict ultimate outcome, may progress
Serial studies required, only applies to germ matrix hem

2. Parenchymal Hemorrhage - extends farther lat than germ matrix
can be "grade IV", but not all II' to germ matrix bleed
most extend from SEH to frontal or parietal lobes
Hypoxia & Hypercapnia implicated as etiology
stress causes vessels to dialte & burst
Phase 1 - echogenic like SEH for 1-2wks
Phase 2 - central Hypoechoic, bright periph rim 2-4wks
Phase 3 - retracts & settles into dependent position
Phase 4 - nec & phagocytosis complete, encephalomalcia
Cerebellar hem best scaned in coronal behind ear
assoc w mortality of 50%, much II' to other premie probs

3. Choroidal Hemorrhage - usually grade II or III
#2 cause of intravent hem not caused by SEH
Difficult to decern from N choriod on US
asym scanning can show marked asym in choroid size
isolated choroid hem simulates vent hem w no hydroceph
Myelomeningocele assoc w lg pedunculated choroid
further inc difficulty in Dx
CT more reliable than US for Dx
DDx - Choroid Papilloma, very rare, consider if CSF clear on tap
all assoc w hydrocephalus, enhance intensly on CT

HEMORRHAGIC NEOPLASMS & CYSTS

1. Malignancy Related Coagulopathy - esp w leukemia & chemo
systemic neoplasms can be assoc w term coagulopathyy

2. Intratumoral Hematomas - 10%, malig astrocytoma #1
neovasc, cent nec, plasminogen activators etc contribute
Heterogeneous, incomplete hemosidrin ring, edema persist
mult lesions & min edema suggests nonneoplastic cause
Cysts & slow growing cystic neo like cranio rarely hem
Oligodendroglioma, neuroectodermal & teratoma hem freq
Ependymoma & choroid tumors - freq SAH & hemosiderosis
Pituitary Adenoma - may hem more freq than astrocytoma
Lymphoma rarly hem unless w AIDS
Renal cell, chorio, melenoma, thyroid & lung mets, 15%

3. Nonneoplastic Hemorrhagic Cysts -rare, colloid cysts never
Rathke cleft cysts & Arachnoid cysts more commonly hem
Arach cysts hem II' to trauma, bridging vessels rupture
sometimes assoc w subdural hematoma

MISCELLANEOUS CAUSES OF BENIGN INTRACRANIAL HEMORRHAGE

1. Amyloid Angiopathy - #1 cause in elderly pt c no htn
nonbranching fibrillar protiens form beta-pleated sheets
Deposit is Cortical & leptomeningeal vessels
extend from sm vessels to brain parenchyma
Contractile elements replaced by the crystals
Mult hem freq & occurs at cortico medullary jxn
basal ganglia & brainstem not affected

2. Infection & vasculitis - rare, inc if immunecompromised
septic emboli - mycotic aneurysms & hemorrhagic infarct
10% of Infective endocarditis have SAH or parenchymal
Aspergillosis & other fungi directly invade vessel
Thrombosis, infarction & hem result
Herpes Simplex II - the only encephalitis assoc w hem

3. Recreational Drugs - 50% have preexisting AVM or aneurysm
Cocaine can induce an acute htn episodes, vasospasm
also enhances platlet aggregation, dural sinus throm
amphetamine & PCP also assoc w hem
endothelial damage & necrotizing vasculitis

4. Blood Dyscrasias & Coagulopathies - iatrogenic or aquired
Vit K def, hepatocellular Dz, antibody against clot, DIC
Anticoag, thrombolytics, aspirin, Etoh abuse, chemo
15% of all intracran hem on anticoag
Supratentorial, intraparenchymal bleeds most common

CRANIOCEREBRAL TRAUMA

MECHANISMS OF INJURY
Projectile Injuries
Nonprojectile Injuries

PRIMARY LESIONS CAUSED BY TRAUMA
lesion directly from initial trauma

1. Scalp - lacerations & subgaleal swelling freq w trauma
penetrating injury - av fistula or psuedoaneurysm poss
assoc w superficial temporal or occipital vessels
subgaleal extrusion of brain thru a comminuted skull fx

2. Skull - fx in 60% of acute head injury, 25% of severe none
Fx occurs by Tension rater than compression
plain film evidence of fx is irrelevent in acute care
Linear fx - assoc w epi & subdural
May "grow" in child due to leptomeningeal protrusion
Depressed fx - assoc w parenchymal inj, less hem
Rhinorrhea or otorrhea - CSF out
Pneumocepahalus - air in sulci & ventricles
Basilar Skull Fx - assoc w CN & vasc damage
Raccoon eys & Battle's Sign (retroauricular bruise)

Temporal Bone Fx - Longitudinal 90%, parallel petrous bone
Facial N damage & otorrhea assoc
Transverse - cause labyrinth & cochlear destruction
3. Epidural Hematoma - 1% of head trauma, 10% of fatal injury
Lucid Interval - delay before deterioration in 50%
usually occur within 24-48 hrs, 20% after neg CT
Fx lacerates the mid meningeal art or dural sinus in 95%
Biconvex, Strips dural attachments, can't cross suture
collects between periosteum (outer dura) & naked bone
95% unilat & supratentorial, infratentorial inc fatality
Poor outcomes II' to delay, may autodecompress thru fx
may see mixed hypo & hyperintense blood w active bleed
II' herniations common
CANNOT cross sutures unless origin is sagital sinus
usually at site of inj, subdural can be countercoup

4. Subdural Hematoma - The most lethal, 50% mortality
10% of all head trauma, 30% of all fatality
Fatality due to shear inj, Subdural II' sign
common in elderly & child abuse w no initial trauma hx
Inc potential space can cause delay in Sx
caused by tearing of bridging cortical veins, <25% w Fx
Crescentic, crosses sutures but not dural attachments
Chronic may be biconvex sim to epidural
Mixed hyper & hypodensity poss, CSF may be present
Rebleeds common, may be isointense if hg <8-10 g/dl
Become isointense P a few days, look for cortical shift
Contrast can help, chronic often loculated, hypodense
Wider window width can also help diff from calvaria
may be bilat esp in child abuse
DDx - hemorrhagic infarct can sim chronic SDH
constrast will show enhancement of infarct, periphery of SDH

Subdural Hygroma - usually II' to chronic subdural hematoma
may be seen w/o hematoma, tear tin arachnoid
NO marginal enhancement
can occur in child w no known trauma, Meningitis, H. flu #1
inc head size & pressure, freq bilat
Menke's Kinky Hair Syn - can be assoc w lg bilat hygromas, atrophy

5. Subarachnoid Hemorrhage - seen w most severe head trauma
Thin high density fluid in sulci & cisterns
Psuedo-subarachnoid Hem - assoc w severe diffuse edema
brain is very low attenuation, dura appear hyperdense
Ventricular blood may enter at tip of lat temporal horn
seperated from ambient cistern by only thin choroid
60% get assoc vasc spasm, occurs at 48hrs & resides by 6-12d
6. Diffuse Axonal Injury - #1 for sig intraaxial morbidity
always w severe closed head inj, lose consciousness
disrupts penetrateing vasc, axons form retraction balls
60% Lobar white matter, esp gray white jxn frontotemp
20% corpus callosum esp post body & splenium
Dorsolateral aspect of pons & internal capsule
CT often initially N despite profound clinical state
Blood in vents may be early clue to severe process
MRI may show multiple T2 hyperintense lesions
Non specific atrophic changes can be a chronic finding

7. Cortical Contusion - #2 cause of morbidity from intraaxial
Loss of consciousness less freq than in diffuse axonal
Superficial foci of punctate or linear hem
Induced by brain striking an osseus ridge or fx line
II' to rupture of small capallaries
50% occur in temporal lobes, 30% frontal
lesions more vis P 24-48hrs, punctate may coalesce
Inc edema & mass effect freq, 20% have delayed hem
MRI more sensitive esp in subacute, inhomogeneous

8. Deep Gray Matter & Brainstem Injuries - 10% of intraaxial
shearing disrupts deep penetrators or stem strikes tent
Assoc w profound deficits & poor prognosis
CT often N, but MRI demonstrates petiechial foci
dorsolat brainstem, periaqueductal gray & deep nuclei

9. Intraventricular & Choroid Plexus Hemorrhage - 5% of heads
assoc w severe trauma, usually other findings as well
subependymal veins disrupted or basal gang hem migrates
poor prognosis, isolated IVH has better outcome
CT shows high density in vents often w a fluid level
can have isolated choroid plexus hem w/o IVH

SECONDARY EFFECTS OF CRANIOCEREBRAL TRAUMA
often more sig than primary manifestations

1. Subfalcine Herniation - #1, cingulate passes under falx
Ipsilat vent compressed, contralat dil II' to monroe obs
Ipsilat ACA & subependymal veins shift & compress

2. Transtentorial Herniation - also freq, 2 types
Descending - uncus & parahippocampus protrude medially
stem shifts away, Ipsi cerebellopontine cist enlarges
early the ipsi suprasellar cist efaces then oblit
PCA, ant choroidal & post comm art displaced infmed
occipital lobe & basal gang ischemia result
periaqueductal necrosis & midbrain (Duret) hem occur
Kernohan's notch - cerebral peduncles compressed
Ascending - rare, vermis & cb herniate upward
central lobule, culmen & sup surface of cb first
sup vermian cistern is effaced, ant disp of 4th vent
midbrain displaced ant, aqueduct obs & hydroceph

3. Tonsillar Herniation - seen w 50% of transtentorial hern
tonsils thru foramen magnum, seen best on sagital MRI

4. Transalar Herniation - frontal lobes disp over sphenoid
Descending - temp lobe & sylvian fissure disp post
horizontal portion of MCA obs
Ascending - same structures pushed over sphenoid

5. Cerebral Ischemia - profound in pts w glasgow score <8
functional imaging may be helpful in determining extent

6. Posttraumatic Cerebral Infarct - occ lobe #1 w tent hern
Cingulate gyrus II' to ACA occlusion w subfalcine hern
MCA assoc w severe global edema or gross hern
Basal gang - lenticulostriate, thalamoperf, choroidal
obstruct against base of skull

7. Secondary Hemorrhage - assoc w infarct or tent hern
periaqueductal necrosis & midbrain (Duret) hem occur
Kernohan's notch - contralat cerebral peduncle comp
may produce ipsilat hemiparesis, false localizing sign
8. Diffuse Cerebral Edema - 20% of severe trauma, kids>adults
unilat edema assoc w ispsi subdural in 85%
usually developes in 24-48 hrs, mortality 50%
effacement of sulci & basilar cisterns #1 early finding
White Cerebellum sign - cb spared, stem & cortex hypo

9. Pneumatocele - develop from sinuses wks to months after trauma
surgical repair of assoc dural tear indicated
rhinorrhea or otorrhea usually stops by onset of pneumatocele

10. Brain Death - cessation of global fxn
no flow demonstrated, Tc99 HMPAO studies most common

VASCULAR MANIFESTATIONS OF TRAUMA
Primary - due to direct effect on vessel, ie stabbing
Secondary - due to process caused by trauma

1. Aneurysm - most are psuedoaneurysm II' to penetrating inj

2. Dissections - media splits forming false lumen
Occurs in ICA w extreme flexion & extention
usually involves seg 2cm distal to bulb
can also occur in petrous w basal skull fx
Midsuraclinod seg is also very susceptable
Postganglionic Horners Syn - assoc w ICA dissection
Occurs in vertebral art between C2 & the skull
can occur intraspinal w fx, or dist to origin

3. Cortical Vein Rupture or Thrombosis - assoc w subdural
rarely isolated, assoc w sinus thrombosis also

4. Dural Sinus Laceration or Thrombosis - assoc w skull fx

5. Traumatic Arteriovenous Fistulae - assoc w rupture
Skull base #1, Carotid - Cavernous sinus fistulae
present w pulsatile exophthalmos

CHRONIC SEQUELAE OF TRAUMA

1. Encephalomalacia - low density on CT, dec T1, Inc T2
assoc w volume loss & vent enlargement

2. Pneumocephalus - assoc w skull fx & dural tear
can be diffuse or focal, low sig on CT, no MR sig
Subdural assoc w AF level, epidural does not move
Subarachnoid & intravent assoc w severe basal trauma
intravasc air assoc w death

3. CSF leaks - usually assoc w basalfrontal fx
sphenoid & ethmoid sinus rhinorhea, assoc w pneumoceph
70% occur in 1st wk, 20% assoc w recurrent meningitis

4. Cranial Nerve Palsies - III, IV, VI, & ophthalmic of V
assoc w complex fx, III also comp by teporal lobe hern
IV damaged by tentorium in violent excursions of brain

5. Diabetes Insipidus - hypothal ischemia from transtent hern

6. Cephaloceles & Leptomeningeal Cysts - assoc w lg skull fx
hern of intracranial contents, usually basalfrontal
may cause a "growing fx"

HEAD TRAUMA ASSOC W CHILD ABUSE
brain damage more likely to occur w/o skull fx
flexible spine & lg head make damage easy
open sutures allow delay of neurologic defects
head trauma occurs in 1/2 of all abuse cases, inc morbid

1. Skull Fx - linear has no assoc, complex or compressed do

2. Subdural Hematoma - #1 assoc w abuse, MRI more sensitive
assoc w mult & diff age subdurals, shaking often cause
assoc w bilat retinal hem

3. Shearing Inj & Cortical Contusion - assoc w poor prognosis

4.Edema & Inchemic Injury - common assoc in neborn to 4y/o
often II' to smothering or strangling

PATTERNS OF EDEMA

1. Intracellular - effects Gray or White Matter
Cytotoxic - loss of ion pump due to infarction etc
Gray matter involvement suggests cytotoxic process
Does NOT respond to Steroid Tx, always followed by vasogenic

2. Extracellular - Effects White Matter only, looser interstitium
Vasogenic - Due to loss of BBB
Neoplasm, inflammation or trauma
Dramatic response to steroid Tx, stabalizes leaky endothelium
Hydrostatic - inc P due to HTN or venous thrombus
Finger like projections of edema thru ext capsule & U fibers

Abcesses & Mets tend to generate more edema than astrocytomas
Meningiomas generate a lg amount of adjacent & deep WM edema
Rapid growth of a lesion is assoc w inc edema
Hemorrhage within a mass etc
Hemorrhage alone however is not assoc w extensive edema
Vascular malformations are not assoc w edema

PATTERNS OF HERNIATION

1. Calverial - fungating brain thru surg or traumatic defect

2. Transtentorial - downward thru Tentorial fissure
Temporal lobe must shift over to fissure before herniation
Cisterns widen on side affected, then obliterate
Uncus in ambient cistern, Contralat lateral vent dilates
Uncus presses thru & pinches CN III, Parasym affected
ipsilat pupil becomes oval & irreg then dilates
PCA compressed, Homonymous Hemianopsia
Midbrain distorts out of usual "Mickey Mouse" shape
Duret Hemorrhage - partial vasc compresion, endothelial damage
hem into brainstem comp reticular sys & resp center, coma
Kernohan's Notch - cerebral peduncle compressed by tent
false localizing signs
Basal Vein of Rosenthal - displaced downward
widened space between basal vein & internal cerebral vein

3. Subfalcial - Cingulate gyrus & ACA herniate laterally
loss of ACA on angio

4. Foramen Magnum - cerebellar tonsils & medulla, assoc w Cb mass

5. Tonsilar Herniation - >5mm in general considered abn
Most common mass displacement due to intracranial lesion
esp severe w masses aligned w clivus: ant frontal or post fossa
also seen w hydroceph from obs at aqueduct
Lhermitte's Sign - pain & "Electric shock" w neck flexion

ATHEROSCLEROSIS
causes 90% of thromboembolic dz & vascular stenosis

1. Etiology - focal endothelial change or subtle injury
allows LDL & macrophage into intima
Sm muscle cells recruited & fill w fatty esters - foam cells
Fibrotic cap covers core of dead foam cells
II' inflammation allows granulation tissue & neovascularity
Plaques hem & necrose acting as nidus for thrombi

2. Imaging - angio remains gold standard, US, CT & MRA also
US - peak sys velocity best parameter for assesing stenosis
flow reversal in post carotid bulb is N
Angio - 1) determine degree of stenosis & ulceration
2) Identify tandem lesions in siphon or intracranialy
3) evaluate existing or potential collateral circ
CT - identifies vessel ectasia & mural calc
MRI - flow voids do not exclude sig stenosis

3. Carotid Origin Stenosis - endarterectamy helps if 70-99%
delayed veiws show "string sign" of high grade stenosis
contrast trickles thru, still benefit from endarterectomy

4. Tandem Lesion - distal stenosis of carotid also seen in 2%
hemodynamic effect additive, usually in siphon, PTA needed

5. Collateral Circulation - critical w severe stenosis or occ
circle of willis #1, complete in only 25%
patent ant comm art usually adequate to allow clamping
ext carotid to ophthalmic good, few others adequate

6. Subclavian Steal - occulusion of prox subclavian or arch irreg
flow reversed in vert art to supply arm & shoulder
post fossa ischemia occurs along w arm pulselessness
Atherosclerotic Dz can effect any prox great vessel or arch

7. Intracranial Atherosclerotic Dz - irreg lumen & stenosis
can lead to tortuous vessels & fusiform aneurysms

CEREBRAL ISCHEMIA AND INFARCTION

1. Physiology - central & peripheral portions differ
Central nidus quickly irretrievably damaged
this is the zone of frank Cerebral Infarction
Penumbra - peripheral cells viable but at risk for hours
Zone of generalized neuronal necrosis, support cells left
Selective neuronal necrosis - only most vulnerable neurons
Ion homeostatsis lost: C++, Na+, & Cl- accumulate
Anerobic glucolysis causes metabolic acidosis
Free Radicals accumulate, cytoskeleton breaks down, cell dies

2. Selective Vulnerability - sensitivity to ischemia varies
Neurons most vulnerable, astrocyts, oligodendro, microglia
Hippocampal pyramidal most sensitive of the neurons
Neocortical layers III, V & VI, purkinje & neostriatum
Thalmus, Basal Gang, Centrum Semiovale susceptable
long single arteriole vulnerable to anoxia & hypoperfusion
Vascular Watersheds - cortex & Cb in adults & term infants
in deep perventricular region in premie babies
Adults - occurs in the WM near caudate or frontoparital
<6% hemorrhagic

3. Hyperacute Infarcts - <12hrs
Angio - usually not done, vessel occlusion most specific
Vascular blush of luxury perfusion in penumbra
delayed arterial emptying, mass effect, collat filling
CT - used to R/O hem & mechanical obs such as mass etc
60% normal at <12hrs, hyperdense art (usally MCA) 50%
Hypodensity of lentiform nuc, assoc w hemorhagic later
MRI - more able to identify early appearance, 10% Normal
N flow void absent, sharp vasc contrast enhancement
T2 hyperintensity does not develop before 8hrs
MR Spectroscopy - detects changes in metabolism
MR Diffusion Gradient - detects intracellular edema

4. Acute Infarcts - 12-48hrs
CT - sulcal effacement, low density basal gang
Gray-White interface lost - Insular ribbon sign
MRI - Hyper T2 develops in 8hrs
assoc w mass effect in 25%, usually mild, max at 5 days
Meningeal enhancement adjacent to infarct
5. Subacute Infarcts - 2 days - 2wks
CT - 24-48hrs wedge shaped area of attenuation visible
Edema & mass effect inc initially, subsides @ 4-7 days
hemorrhagic transformation at 1-3 days, freq if large
Gyral effacement at 4-7 days
Contrast enhancement from BBB breakdown, gyral or RING
develops at 3-4 days & can last 8-10 wks
20% seen only w a contrast scan, but NOT good for Pt
MRI - meningeal & intravasc enhancement dec at 2-4 days
parenchymal enhancement begins & can last for wks
T2 begins to fade as protiens from cell lysis spill
1-2 wks - T1 post-contrast striking, T2 Normal
Wallerian Deg - hypodense band in corticospinal tract

6. Chronic Infarcts - > 2 weeks
Gliosis & volume loss are hallmark of stroke residua
Both CT & MRI show well delineated encephalomalacia
Ipsilateral ventricle enlarges, dystrophic calc rare
Hemmorhagic areas develop predictably

7. Lacunar Infarcts - 25% of all strokes, basal gang & thal #1
effect single long penetrating vessel to deep cerebral gray
CT - usually only seen w assoc WM disease
MRI - dec T1, Inc T2 - DDx - subependymal myelin pallor
or Virchow-Robin - enlarged perivasc spaces

8. Hypoxic-Ischemic Enchephalopathy - global rather than focal
Etiology is prolonged hypotension, asphyxia, or CO poisoning
Basal Ganglia & border zones most sensitive
Pseudolaminar Necrosis - Generalized cortical ischemia
layers III, V & VI effected along w caudate & putamen

9. Hemorrhagic Infarcts - easily detected by CT
MRI - standard images have poor sensitivty

10. Cerebellar Infarcts - rare due to extensive collarterals
Present w Vertigo, ataxia, nausea & vomiting
90% occur in PICA distribution, congenital abscence
25% enhance, most at subacute, gyral or ring

CT Finding Summary - N up to 24hrs
Peak mass effect at 2-5d, gone by 2nd wk
Peak enhancement in 2nd wk, predominately gray

SPECIFIC VASCULAR DISTRIBUTIONS
TIA best assesed w common carotid inj w 10cc of 60% contrast
circulation time for cerebral vasc = 6sec

1. Anterior Cerebral Artery - variable sup, med & lat borders
inf border w MCA at orbitofrontal gyrus
pericallosal branches to septum pellucidum & ant 2/3 corpus
Infarcts rare - usually sm on ant interhemispheric fissure
extensive PCA & MCA collaterals

2. MCA - supplies entire lat hemisphere & ant temp lobe
lentiform Nuc & portions of caudate also
75% of strokes, often ant or post only

3. PCA - supplies most of inf occipital lobe & post limb of int capsule
#2 to MCA infarcts - calcarine, thalami & midbrain
may originate from MCA anastamosis, not seen of vert art injection

4. Ant & Post Choroidal Art - PCA branches, rarly seen on images
globus pallidus, optic tracts, uncus, amygdala, & choroid pl

5. Perforating branches - Arise from circle of Willis
Supply basal structures, produce lacunar infarcts

6. Basilar Art - pons, mesencephalon, post thalami
Locked in Syndrome - lg ventral pontine infarct

7. Sup Cerebellar Art - from dist basilar, supply entire sup Cb
Vermis & deep Cb WM also

8. Ant Inf Cerebellar Art - from prox basilar, smallest Cb art
supplies flocculus & middle Cb peduncle, infarct rare

9. Post Inf Cerebellar Art - 90% of Cb infarct, 20% congen absence
Supplies Entire postinff Cb & postlat medulla
Wallenberg Syndrome - effects CN V, IX,X, Ataxia, horner syn
facial pain & numbness, diminished Gag & taste, N/V
nystagmus, Diplopia: all Ipsilat, contralat numbness from spinothalamic

10. Post Meningeal Art - originates from vert art
below formen magnum but sup to arch of atlas

11. Ophthalmic Art - 1st branch of supraclinoid ICA
supplies ant meninges, retrograde flow seen in ICA occ

NONATHEROMATOUS ARTERIAL NARROWING

CONGENITAL ABNORMALITIES

1. Congenital Aplasia or Hypoplasia - rare in carotid
Vertebral art hypoplasia common N variant

2. Von Recklinghausen Dz - NF-1, freq assoc w vascular abn
90% occlusive or stenotic, AVM's & aneurysms also
Moyamoya pattern of collaterals may develop
Aortic, celiac, mesenteric & renal vasc stenosis also seen
Non seen w NF-2

3. Tuberous Sclerosis - progressive deg & aneurysm poss but rare

4. Moyamoya - Idiopathic progressive arteriopathoy of childhood
etiology unknown, cerebrovasc progressively occludes
dist ICA & prox MCA #1, mult collaterals develop
lenticulostriate, thalamoperforators, leptomeningeal, dural
mult infarcts in 80%, atrophy in 50%, all Japanese

5. Menkes' Kinky Hair Dz - X-linked neurodegenerative syn
defect in copper met, mental retard, seizures, stubbly hair
Tortuous elongated vessels in abd & brain
Large bilat subdural hygromas & cortical atrophy also poss

6. Sickle Cell Anemia - stroke occurs in 10%
mult atypically located aneuryms


CONGENITAL VASCULAR INSULTS

1. Porencephaly - unilocular cyst from genetic defect or injury before 26wks
in utero insult only, communicates w the ventricles
Fetal brain cannot make glial scar, very smooth walled
Agenetic Porencephaly - insult during or before cortex formation
Cavities assoc w agyria, pachygyria, polymicrogyria & heterotopia
septal & corpus callosum abn occur at same time
Schizencephaly is an example of this
Encephaloclastic Porencephaly - Destructive type
Necrotic softening or already formed cortex
NO assoc malformation, septum & corpus intact
Fewer septations than encephalomalcia in general
2. Hydrancephaly - bilat destruction of all solid cerebral tiss in utero
severe form of encephaloclastic porencephaly
only thalmus & brainstem remain, NO residual ependyma or vents
thin mantle of cortex w intact septum pelucidum & falx
Microcephaly possible, often N head size
Usually massive vasc insult, in utero infection poss
Shunt therapy does not improve outcome as w hydrocephalus
Hydroceph may have very thin mantle which thickens w shunt
Angio showing NO MCA poss w hydranceph, not w hydroceph

3. Multicystic Encephalomalacia - infectious or vasc insult after 26wks
Occurs II' to increased intracranial pressure, ie edema P anoxia
small vessels to periphery compressed in sulci
Ant & middle dist predominate, post & deep preserved
Walls of vents intact, NO communication w vents
Characteristic progression in very young CNS system
Rapid liquefacation & dissolution of nec tissue
complete clearance by macrophage, minimal gliosis
Sequence starts w birth trauma, Detected at 2wks, complete at 8wks
Mult bilat cysts of diverse sizes & shapes, "Swiss Cheese"
Thin septa can be shaggy
II' distortions occur as remaining tiss replaces lost portion

4. Neonatal Cerebral Infarction - more often arterial than venous
Emboli #1 - cardiac, placental or umbilical vein origin
20% of Congen heart pts, esp Tet & most P cath or surg
DIC & Sepsis are commonly assoc, most die quickly
more often mult in premie, 2:1 in left over right
II' hemorrhage occurs more freq than adults
Venous infarcts occur due to stasis in sag sinus II' to heart Dz

Periventricular Leukomalacia - nec of periventricular WM, esp at trigones
watershed region fed by ant, middle & post, echogenic initially
may progress to cystic deg by 3wks, hem poss
30% of premies, inc if younger or on vent
Note - do not mistake the N echogenicity of peritrigonal WM
DDx - transependymal edema, not preceeded by echogenic period

5. Infarct in Children & older infants are more often venous
Dissections, infection, Drug abuse & blood dyscrasias also
Neurofibromatosis, Tuberous Sclerosis & tumor poss
AQUIRED CAUSES OF NARROWING & OCCLUSION
Vasculitides are a heterogeneous & rare CNS disorder
inflammation & necrosis of vessel walls

1. Infectious Arteritides
Bacterial Meningitis - freq cause of aquired vasc dz in kids
H. flu #1, infarction develops in 25%

Tuberculous Meningitis - Supraclinoid ICA most often effected

Mycotic Arteritis - all poss but actinomyces directly invades
may produce mult hemorrhagic infarcts

Viral Arteritis - herpes encephalitis most common
hemorrhagic & necrotizing esp in parietal & temp lobes

Syphilitic Arteritis - Gummas most often effect MCA


2. Noninfectious Vasculitides
Polyarteritis Nodosa - #1 systemic necrotizing vasculitis
freq widespread organ dysfunction, CNS occurs late
Microaneurysms from int elastic lamina necrosis pathog
thrombosis, irreg & stenosis comes later

Sytemic Lupus Erythematosis - effects CNS & peripheral Nerve
Stroke occurs in 50%, true vasculitis is rare though
most from cardiac valvular Dz or antiphospholipid Ab Dz
MRI - mult subcortical regions of inc T2, may enhance on T1
these may hem or calc esp in basal gang & dentate
Angio - mult progressive arterial thrombosis

Cell Mediated Disorders
Sarcoidosis - CNS effect in 5%, infil w nonnecrotizeing gran
enhancing nonthickend leptomeninges esp at basilar & vasc stenosis
Wegener Granulomatosis - CNS effect in 30%, 2 types of lesion
granulomatous invasion from paranasal sinuses
Vasculitis of the nervous system w irreg & occlusion
Takayasu arteritis - granulomatous infil into art wall, 9:1 female
a giant cell arteritis, lg vessels of aortic arch, esp L subclavian
Temporal arteritis - systemic type giant cell arteritis, elderly pts
both cause occlusion, stenosis, luminal irreg & ectasia
Granulomatous angiitis - sm vessel vasculitis, unknown etiol
3. Miscellaneous Vasculatides
Kawasaki Dz - mucocutaneous lymph node syn, ectasia & aneurysms

Thromoangtis Obliterans - Buergers, obliteative vasculopathy
effects med & sm art of extremities, CNS venous occlusion

Behcet Dz - immune related vasculitis of art & veins
Japan & middle east predominatly
Recurrent oral & genital aphthous ulcers, uveitis, arthritis
CNS in 45%, organic confusion, brainstem or meningoenceph syn
Foci of inc T2 in brainstem & diencephalon, stenosis & occ

Drug Induced Arteritis - direct toxic inj to vessel wall
Amphetamine - necrotizing cerebral angitis, saccular aneurysm
vasospasm of small & medium vessels, stroke also
Cocaine - blocks presynaptic reuptake of norepi & dopamine
Hem, ischemia, infarction, seizures, vasospasm & death
Tx - steroids are very effective in reversing

4. Miscellaneous Vasculopathies
Fibromuscular Dysplasia - intimal & medial prolif in ICA & vert
"string of beads" seen around C2 level, 65% bilat, unknown etiology

Flow related Vasculopathy - II' to AVM etc, ectasia, stenos etc
intimal destruction & thickening

Extrinsic Compressive lesions - tumors, phytes, fibrous bands
cause local narrowing & irreg
infection or abcess can cause sim but more diffuse problems

Radiation Vasculopathy - can denude & ulcerate endothelium
emboli, stenosis etc, local brain gliosis & necrosis assoc
5. Dissection - cause of stroke esp in young people
Trauma - blunt, penetrating or stretching
Vasculopathies - f. dysplasia, Ehlers-Danlos, Homocystinuria
Angio often shows long midcervical narrowing that spares bulb
Vert usually between C2 & skull base
MRI very good at detecting narrow lumen & paravasc hematoma

Carotid Dissection - many asym, often resolve spontaneously in 1-3mo
most dissect to base of skull & are surgically unreachable anyway
Dist emboli & occ poss, psuedoaneurysm worsens prognosis
"String-Sign" & visulaization of false channel freq
most II' to trauma, marfans, FMD
50% of post-traumatic type result in Horner's syn

6. Stroke Mimics - Tumor & subdural can present as focal defects
tumors can follow vasc distributions
Strokes - effect the cortex & spare the WM, wedge & sudden
Tumors - effect the WM & spare the cortex, round & gradual
Gyriform enhancement - stroke, encephalitis & contusion freq
also seen post-ictal & w infiltrating neoplasms - BBB loss

VENOUS INFARCT

1. Pathology - multistep, usually thrombosis starts in sag sinus
progress to bridgeing veins & cortical tributaries
petechial perivascular hem & cortical venous infarct follow
Internal Cerebral V thrombosis rare but devastating
extend to V of Galen & cause deep gray matter infarcts
NO specific vascular territory, tend to hemmorrhage more often
predominately WM lesions

2. Etiology - none in 25%, sinusitis, trauma, tumor, dehydration
oral contraceptives, pregnancy, inflam bowel dz

3. Angio - Arch injection fills all systems, prevents coll inflow
empty channel seen w dilated collaterals
origin of cortical veins may opacify, "hang in space"

4. CT - empty delta sign w hypodense thrombus, engorged tributary
cortical & subcortical hem, thickend falx, Shaggy tentorium
in newborn physiologic polycythemia can make falx thick
Psuedodelta - SAH or SDH can make sinus appear less dense
unmylenated brain of newborn can make sinus less dense
post sag sinus may split early
Contrast demonstrates Gyriform enhacement

5. MRI- appearance varies w age
Acute - iso T1, Late Acute - hyper T1, hypo T2
Subacute - hyper on all sequences
Chronic - fibrosis w development of extensive collaterals
artifact can be created by flow, deciving either both ways

CONGENITAL & NEONATAL INFECTIONS OF THE BRAIN
TORCH - TOxoplasmosis, Ruebella, CMV, Herpes

1. CMV- #1 cause of congenital infection, 3X toxoplasmosis
infects only humans, DNA virus related to herpes
Tranplacental transmission, 70% to brain, 60% multiorgan
Cytoplasmic inclusions in glia, microglial nodules on micro
Germinal matrix invaded - widesread periventricular necrosis
Presentation - Jaundice, thrombocytopenia & chorioretinitis
Seizure, MR, optic atrophy, sensoneural deafness later
most latent, reactivated if immunecompromised
MRI - Severe Migrational anomalies occur in 2nd trimester
lissencephaly, pachygyria & hydrocephalus
delayed myelin, Paraventricular cysts
causes patchy spongiosis, encephalomalacia & microcephaly
US - show ring like hypoechoic zones behind calc - pathog
CT - Central periventricular calc is the usual finding
DDx - toxo very similar, use Ab titer for specific viruses for Dx

2. Toxoplasmosis - intracellulaar protozoan, transplacental inf
Induces a necrotizing granulomatous rx on micro
signigicant only if maternal inf during 1st 26wks
Presentation - nonspecific, spont abortion if very early
TRIAD - Hydrocephalus, bilat chorioretinitis, scattered calc
basal gang & cortex primary sites of calc
ependymitis causes periaqueductal necrosis & stenosis
NO migrational anomalies
CT - in general calc not as central as CMV

3. Rubella - Transplacental during maternal viremia
interferes w cellular multiplication & prolif of glia & neuro
Micro - parenchymal vasculopathy & perivasc necrosis in WM
Presentation - 8-12wks severe, 6-9mo often asym
Imaging - nonspecific, subependymal cysts & microceph
delayed mylination & ischemia from vasc injury
extensive basal ganglia calc freq
CT - both periph & central calc assoc w occular abn
4. Herpes Simplex - Type II causes 90%, aquired during birth
intrauterine infection causes spontaneous abortion
Generally appears in 2-4wks, incubation period
Type I (oral) - aquired from contact P birth
Micro - attacks vasc endothlium, thrombus & hem infarct
can effect any cell, microglial nodules & inclusions also
Presentation - diffuse brain involvement in infants
Temporal & cingulate gyrus localization in kids & adults
Progresses to severe encephalomalacia, Treatable so don't miss it
MRI - hyperintense cortical gray on T2 most specific
hemorrhagic changes, atrophy & meningeal enhancement also
Congenital form does NOT localize to basal gang, only late
CT - not assoc w calc

5. HIV- 80% of children from placental, 1/3 of maternal pass it
Micro - multinucleated giant cells, perivasc calc in basal g
II' infection LESS common, I' retroviral encephalitis #1
50% develop progressive encephalopathy, development delay
Microceph & spastic paralysis, but Seizure RARE, dead 1yr

6. Varicella - transplacetal in 25% of maternal viremia
Severe necrotizing encephalomyelitis seen at up to 7mo gest
Ant horn & dorsal root ganglion cells most affected

. Enterovirus - Coxsackie A & B, echovirus & polio
no assoc w CNS dz or malformations intrauterine
Postnatal - diffuse menigoencephalitis
olivary nuc & vent horns of spinal cord lesions freq
only 1% of polio infections progress to neuro defects

8. Hemophilius Influenza - consider H. flu if bilat subdural hygromas
common cause of pulm infection in children

MENINGITIS
#1 form of CNS infection

ACUTE PYOGENIC MENINGITIS

1. Etiology - caused by bacteria, varies w age
neonatal - group B strep, E. Coli, Listeria monocytogenes
Child <7y/o - H. flu
Young adult - Neisseria Meningitidis
Older adult - Strep Pneumoniae
Hematogenous spread or local extention, trauma also
Can follow emissary veins from scalp to dural sinus

2. Imaging - fibrinous purulent exudate fills basal cisterns
can extend to fill entire sub arachnoid space
can cause vasospasm & venous infarction, alter BB Barrier
CT - usually N in acute phase, used to follow progress
Vent & sub arachnoid space enlargement
50% have meningeal enhancement
MRI - demonstrates obliterated cisterns
more marked enhancement extending deep into sulci
cortical veins pushed out of sulci
DDx - TB also prefers the basal cisterns

3. Complications - seen in 50%, noncommunicating hydrocephalus
Ventriculitis w exudate blocking aqueduct
Subdural effusion or empyema, freq seen in children
Empyemas freq caused by extention from the sinuses
Parenchymal abnormalities in 10%, cerebirtis to frank abcess
Abcess only forms if immunecompetent
Cerebrovascular - 27% of children develop cerebral infarction
37% of adults, vasospasm, vasculitis etc


ACUTE LYMPHOCYTIC MENINGITIS
Viral origin, most benign & self limited
Sx similar to bacterial but less severe
Imaging usually N unles coexisting w encephalitis

CHRONIC MENINGITIS

1. Etiology - TB #1, usually by hematogenous spread
Coccidiomycosis & Cryptococcus also
becoming more common w HIV, drug abuse & inc immigrants
25% die, 75% have long term sequela - midbrain infarct
Children have mostly miliary brain TB, only 5% isolated lepto

2. Imaging - Thick gelatinous exudate primarily in basal cisterns
TB causes caseous necrosis, granulomas & endarteritis
CT - "En Plaque" dural thickening, "Popcorn" dural calc
abn enhancement of dura may be seen years P initial inf
MRI - unenhanced scans DO NOT detect active meningeal inflam
Conspicuous on post-contrast T1
Calcific meningeal nodules markedly hypo on all sequences

3. Subdural Empyema - Frontal sinusitis #1, surg & trauma also
Mass effect greater than would be seen w sim size hematoma
Inflam causes BBB breakdown & venous thrombosis
assoc w marked enhancement of adj parenchyma
look for source of infection, ie sinusitus, epidural also possible

4.Epidural Abscess - less freq & less severe, > P surg than subdural
Freq adjacent osteomyelitis, seen w plain film
Much less inflam rxn in adj brain, mass effect sim to hem
Both subdural & epidural puss are surgical emergencies

PYOGENIC PARENCHYMAL INFECTIONS

CEREBRITIS & ABCESS

1. Etiology - usually hematagenous spread from extracranial site
30% have more than one organism: strep, staph & G negatives
Children more frequently from meningitis

2. 4 Stages of Pathology
Early cerebritis - 3-5d, focal but not localized
mass of congested vessels, PMN's & edema
no frank tissue destruction
CT - N or only faint hypodense region & edema
MRI - T2 hyperintense, faint post-enhancement on T1

Late Cerebritis - 5-14d, sm necrotic zones coalesce
ill defined ring of inflam cells, fibroblasts & gran tiss
CT - irreg enhancing rim may develop, may fill in w delay
MRI - necrotic zones become hypointense on all sequences
intense rim enhancemet, extensive peripheral edema
satelite lesions freq visualized

Early Capsule - 2 wks, collagen & reticulin form a capsule
mass effect & edema decrease as capsule matures & thickens
Gliosis develops around abcess periphery
CT - shows thin capsule w strong "ring enhancement"
ring thickest near cortex, opposite neoplasm
ring also smoother on outer margin than on inner
MRI - capsule becomes hypointense on T2

Late Capsule - 3 layers, inner inflam, mid collagen, & glial
CT - shows progressive shrinkage
3. Location - gray-white juxtion of parietal & frontal lobes #1
mult only in immunecompromised
Spreads on ant-post assoc tracts, can't follow commisures

4. Tc99 HMPAO - a WBC label using IgG
may be helpful to DDx abcess form neoplam

5. Immunocompromised - often unusual opportunistic bugs, rare
steroids can decrease edema & mass effect
walls may be thicker & more irreg, harder to DDx from Ca
Toxoplasmosis most common in AIDS pts

6. Complications
Satellite abscesses - daughter lesions occur by capsule break
Ventriculitis - most freq following shunting & surgery
intravent abcess rupture poss, medial wall thinnest
diffuse enhancement of ependyma
Choroid Plexitis - primary route of bugs to brain
II' involvement poss
Meningitis - can occur w or w/o abcess rupture
ENCEPHALITIS
Diffuse nonfocal brain parenchymal inflammation
Viral #1, 99% herpes in immunecompetent
Effects limbic sys first, poss due to CN I entry site
Insula & Cigulate gyrus first to show inc T2

1. Herpes Simplex - Transported along sensory roots of CN V or I
HSV type II (genital) infects neonates, diffuse & nonfocal
HSV type I if older, 30% <20y/o, focal esp in limbic sys
often unilat initially w less severe contralat later
Fulminate necrotizing meningoencephalitis w massive necrosis
petecial & confluent hem assoc w vasculitis
Inclusion cells seen in cyto of neurons & glia
Presentation - seizure, fever, altered mental status
Rapidly progressive w 70% mortality
CT - often N initially, Hem suggestive but usually late
low density lesions in temp lobe w mass effect
patchy or gyriform enhancement poss, dense gray in type II
MRI - gyral edema on T1, bright temproal or cingulate on T2
may extend to insular cortex but spare putamen
enhancement following contrast unusual early on
Foci of hem often seen (use T2*), always present at autopsy
Bilat involvement by 2 wks
Encephalomalacia, atrophy & dystrophic calc late sequela
Poss in immune comp pt but rare

2. HIV encephalopathy - progressive subcortical dementia
Virus itself infiltrates early & in 60%, Not opportunistic
10% develop neurologic sx before anything else
Demyelination, gliosis & infil w multinucleated giant cells
MRI - T2 shows diffuse patches of inc signal in deep WM
frontal lobes #1 gray usually spared, bilat but asym
NO mass effect
3. Toxoplasma Gondi Infection - obligate intracellular parasite
#1 opportunistic infection in AIDS patients
Basal galnglia & cerebrum at corticomedullary jxn #1
Lesions form 3 distinct zones w no capsule
inner zone of coagulative necrosis
middle zone hypervascular w numerous inflam cells
outer zone of encysted organisms, surrounded by edema
CT - solitary or mult ring inhancing lesions, check for orbit involvement
MRI - T2 more sensitive than enhanced T1
DDx - I' CNS lymphoma, Usually a solitary lesion
lymphoma tends to be periventricular w subependymal spread

4. Cryptococcosis - enters via respatory, hematogenous to CNS
Meningitis #1 in immunecompromised, seen in 10% of AIDS
Gelatinous Cryptococcomas - dilates perivasc spaces, WM edema
Multifocal basal ganglia & midbrain hyperintensity on T2
Gelatin obs CSF causing hydrocephalus
Minimal inflammation results, no abcess, no enhancement

5. Progressive Multifocal Leukoencephalopathy - immune comp pt
Oligodendroglia destroyed by Papova virus, demylinates
4% of AIDS, subcortical first, lesions become confluent
Asymetric, Hyper T2, cavitary late, NO enhancement

6. CMV - rare, extends along subependymal surfaces
Simulates CNS lymphoma w thick nodular confluent perivent rim
Low density on CT, can also have subtle WM change only
NO calc as seen in neonatal CMV

Note - CNS Lymphoma is 1000x more common in AIDS than N
Also has subependymal spread, fluffy borders
significant edema & mass effect

7. Neurosyphilis - Treponema Pallidum, can occur at any stage
Sm vessel endarteritis of meninges brain & cord
Gummas - isolated & peripheral
4% of AIDS pts
8. Intracranial TB - 10% of AIDS, 40% get parenchymal involvement
hydroceph & meningeal enhancement #1
CT - dense basilar exudate seen, can sim SAH

9. Arbovirus - spread by ticks & mosquitoes
Easter, Western & Venezuelan Equine encephalitis

10. Ebstein-Barr Virus - can cause persistent enchephalitis
Transient WM & thalmic lesions

11. Creutzfeldt-Jakob Dz - Spongiform encephalopathy
sim Alzheimer's, also known as Slow virus infection

12. Acute Disseminated Enchephalomyelitis - immune mediated, sim MS
Preceeded by viral illness, clears w no remission
Diffusely spread thru WM w no perivent prevelance like MS

POSTINFECTION ENCHEPHALITIS
1. Subacute Sclerosing Panencephalitis - occurs yrs P measles inf
elevated titers of measles neutralizing Ab found
Perivasc lymphocytic infil assoc w demylination & glia loss
Hypodense foci in subcortical & pervent WM, enhance
Death in 2-6 yrs

2. Acute Disseminated Encephalomyelitis - immune mediated rxn
triggered by virus or vaccination, Lyme dz included
perivasc inflammatory infil assoc w demylination
Perivasc astrocytosis seen as the disease resolves
Starts 1-3wks P infection, rapid progression to multifocal sx
death poss, some recover completely

MISCELLANEOUS INFECTIONS

TUBERCULOSIS
hematogenous dissemination, usually causes meningitis
Tuberculomas - casseating granulomas, 1/3 multiple
miliary only in children
M. tuberculosis #1, Avium-Intracelulare rare in CNS
cortex & basal gang in adults, Cb in children
CT - hypodense due to cerebritis early, ring enhancing
Predilection for basilar cisterns, calc after healing
MRI - tuberculomas are iso on T1 w marked enhancement
T2 shows central hyper w ring of hypo II' to gliosis etc
DDx - encapsulated abcess, astrocytoma


FUNGAL INFECTIONS
Immunecompetent - histo, coccidio & blasto, true pathogens
Oppurtunistic - aspergialla, candida & crypto
Granulomatous rxn most common in CNS, infil & abcess also
aspergilla invades blood vessels, Hemorrhagic Mycetomas
coccidio - meningeal inflamm, purulent casseous granulomas
direct extention from sinuses or hematogenous spread

PARASITIC INFECTIONS
Toxoplasmosis, Cysticercosis, Shistosomiasis, Echinococcus

1. Neurocysticercosis - Tenia Solium, #1 CNS infection in world
Humans & pigs are definitive host, Adult worm in sm intestine
Lavae enter blood stream, then to muscle & CNS
CNS involvement in 90%, corticomedullary jxn #1
intraventricular cysts in 50%, subarachnoid 10%
Epilepsy results in 50%
Dead larvae incite intense inflam rxn - #1 cause of morbidity
Mult stages - Vesicular, granular nodular & nodular calcified
Vesicular - thin capsule, viable larvae, no inflam
Vesicular Colloidal - larvae dies, fluid turbid, shrinks
metabolic products released disrupting BB barrier
fluid more hyper than CNS, ring enhancement begins
Granular Nodular - cyst retracts & thickens, scolex calc
becomes iso to hypo on MRI
Nodular calcified - completely mineralized, no inflam

2. Echinococcosis - HYDATID CYST, dog tapeworm
Ova hatch in GI, spread to every organ via portal circ
Liver 65%, lung 20%, CNS 2%
Single thin walled sphere w CSF density in parietal area
5% of all intracranial masses in endemic areas

3. Paragonimiasis - fluke in undercooked fish, CNS involved in 1%
conglomerate ring enhanceing abcesses w marked periph edema

NORMAL MYELINATION
Begins at 5th fetal month & continues thru life
Caudad to cephalad, dorsal to ventral, central to peripheral
Sensory before motor
T1 - myelination hyperintense
T2 - myelinated portions hypointense

Birth - medulla, dorasal midbrain, int capsule & cb peduncles
T2 - unmyelinated protions very hyper relative to cortex
opposite of adult pattern

3 months - deep cb WM, vent brain stem, corticospinal tract
T2 - now lower signal thruout cerebral WM

4 months - first appearance in splenium of corpus collosum

6 months - Genu now hyper on T1
T2 - centrum semi-ovale begins losing hyper signal

8 months - approaches adult pattern, anteriofrontal only exception

3 years - only association tracts around ventricular trigones remain
these may remain hyper on T1 until 20-30yrs

CONGENITAL DISORDERS OF WHITE MATTER
The Leukodystrophies, myelination disorders
Enzyme deficiencies that cause abn formation or destruction
Always R/O periventricular leukomalacia from a vasc insult

1. Metachromatic Leukodystrophy - Lysosomal Disorder, Auto Rec
deficient catabolic enzyme Arylsulfatase A
Confluent demylination esp ant, spares subcortical U fibers
lipid material collects in peripheral & centeral WM
moderate vent enlargement, no enhancement
Diffuse inc T2, thalami hypo, cortical atrophy late
80% onset at 1-2yrs, death in 6mo, adult forms sim

2. Krabbe Disease - Lysosomal Disorder, Auto Rec
def lysosomal hydrolase galactocerbroside B-galactosidase
Extensive sym dysmyelination of centrum semiovale & corona
Cb WM much less effected unlike MLD, Thalami HYPER dense
Subcortical U fibers spared as in MLD, diffuse inc T2
Freq infantile onset, adult also, rapidly progressive & fatal
Severe progressive atrophy seen in infantile form

3. Adrenoleukodystrophy - Peroxisome disorder, X-linked, LORENZO
disorder of intracellular organelles, no long-chain FA met
deficient acyl-CoA synthesase
Probable Dysmyelination from a early age
Demyelination starts at occipital lobes & Corpus C splenium
spreads from peritrigonal regions outward & ant
CNS abn preceeds adrenal abn in 80% of cases
Marked Enhancement of advancing periph rim, outer edema
MRI - shows 3 distinct Zones w central necrotic zone
symetric hyperintensity in post limbs of int capsule
frontal & temporal WM is spared
Males 3-10yrs, Visual & behavioral abn #1 presentation

Adrenomyeloneuropathy - variant effecting cord & periph Nerves
esp thoracic cord

Zellweger syndrome - variant w multiple enzyme def
peroxisomes absent, affects both gray & WM
4. Pelizaeus-Merzbacher Disease - Lack Myelin specific proteolipid
Oligodendrocytes unable to differentiate & Survive
X-linked or Auto rec, typically in young boys, dead at teens
Brain & Cb atrophic, complete lack of myelin in all parts
Difficult to detect on CT, MRI shows diffuse WM abn
Cb, Diancephalon & subcortical tracts may be spared
"Tigeroid" pattern of spared myelin
Rotary Nystagmus is a characteristic finding

5. Alexander Dz - Sporadic, unkown etiology
Massive Rosenthal fiber deposits, Brain INCREASED in size
Rod like cytoplasmic inclusions in astrocytes
deposit around vessels, Basal gang, thalmaus & hypothal
Frontal lobe WM effected 1st, presents in infancy, death 2yrs
Juvenile & Adult forms also, longer course, sim MS
CT - low attenuation in frontal WM & basal gang
MRI - T2 hyperintense in effected areas

6. Canavan Dz - Spongy Degeneration of the brain
N-acetylaspartylase def, accum in brain, plasma & urine
INCREASED brain wt & vol, WM demylinated & gelatinous
Prefers the Subcortical U fibers, gyriform pattern seen
internal capsule spared
Infantile & Juvenile forms seen, death before 5y/o

7. Amino Acid Disorders
Imaging non-specific in this & all Amino Acid disorders
varied degrees of demylination, usually perivent
MRI usefull to asses effectiveness of dietary restrictions

Phenylketonuria - common Auto rec, 1:14,000
defective hepatic phenylalanine hydroxylase
phenylalanine cannot be converted to tyrosine

Maple Syrup Urine Dz - rare Auto rec, urine smells like maple
Branched chain Amino Acids cannot be catabolized
Presents 4-7 days P birth, marked edema seen on CT if no Tx<