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Case 1

40 year old woman presenting with headache

Epidermoid

Ectodermal inclusion cyst

CSF-like mass insinuates cisterns, encases nerves/vessels

Location

90% intradural

CPA (40-50%)

4th Ventricle (17%)

Cerebral hemispheres (1.5%)

Intraventricular within tela choroidea

10% extradural: Skull (intradiploic within frontal, parietal, occipital, sphenoid skull as well as spine

Epidermoid

Lobulated, irregular, “cauliflower-like” mass with “fronds”

CT findings

> 95% hypodense, resembling CSF

10-25% Ca2++

Intradiploic epidermoid: Bony erosion with sharply corticated margins

Epidermoid

T1WI

~75% slightly hyperintense to CSF on T1

Lobulated periphery may be slightly hyperintense than center

T2WI

65% isointense, 35% slightly hyperintense to CSF

FLAIR

Ususally doesn’t completely null

DWI

High Signal

ADC = brain parenchyma

T1+C

Margins may enhance (35%)

Epidermoid

Demographics

20 -60 years old; peak 40 years old

M=F

Pathology

Cyst filled with soft waxy or flaky material

Mother of pearl outer surface

Congenital

Ectodernal inclusions during neural tube closure

CPA epidermoids derived from cells of first branchial groove

Acquired

Rare but more common in spine s/p LP