Go Back Brain/11. Calvaria, Scalp/Neoplasm, Neoplasm-like condition/11.3 Intradiploic Epidermoid/ Go to Index

Headache

Intradiploic Epidermoid

Epidermoid definition

Congenital inclusion cysts of ectodermal elements

Grows by progressive desquamation with conversion to keratin, cholesterol crystals

May be acquired from trauma

General Features

Location

90% intradural primarily basal cisterns

Cerebellopontine angle 40-50%

4th ventricle 17%

Parasellar/Middle cranial fossa 10-15%

Brainstem, cerebral hemispheres rare

Intraventricular temporal horn, 3rd, 4th ventricles

10 % extradural

Skull (intradiploic) and spine

Skull Intradiploic Lesions

May alter scalp, inner and outer skull tables

Typically round or lobulated

Well deliniated with sclerotic rim

Radiographic Appearance

CT

Round lobulated mass, typically hypodense resembling CSF, 10-25% have calcifications

“dense” epidermoid – secondary to hemorrhage, high protein, saponification of cyst debris to calcium soaps or iron containing pigment.

MRI

T1- often slightly hyperintense to CSF

White Epidermoid- hyperintense to brain due to high concentration of triglycerides and unsaturated fatty acids

Black Epidermoid- hypointense to CSF due to presence of solid cholesterol crystals and keratin and lack of fatty acids and triglycerides

T2- Isointense 65%, Hyperintense 35%

Diffusion- restricts diffusion

T1+c- usually none margin may show enhancement.