“White” epidermoid cyst
- Background
- Epidermoids arise from inclusion of ectodermal elements during neural tube closure and are more common in young adults.
- CP angle is most common location (5% of all tumors in this region), followed by supra- and para-sellar regions.
- Clinical Presentation
- May be asymptomatic for many years. Symptoms are mainly due to mass effect and/or involvement of cranial nerves.
- Key Diagnostic Features
- Extra-axial intradural mass predominantly hyperintense on FLAIR and T1WI caused by semiliquid cystic contents with high protein concentration, variable T2 features, restricted diffusion, and no contrast enhancement.
- High CT density.
- Lesion has a cheesy consistency, insinuates into adjacent cisterns engulfing blood vessels and nerves.
- Differential Diagnosis
- Dermoid: T1 bright and generally midline. May be impossible to distinguish from white epidermoid.
- Cystic schwannoma: Purely cystic lesions are very rare, extension into the ICA and enhancement of the wall are present.
- Cystic meningioma: Dural-based attachment to tentorium or petrous dura (dural tail), contrast enhancement of solid components.
- Neurenteric cyst: More common in the spine, can present as an intracranial extra-axial cystic lesion with variable signal intensity on T1 and T2, most commonly found in posterior fossa
- Arachnoid cyst: Smooth margin, do not enhance after contrast administration.
- Classic epidermoid: Low T1 signal, high T2 signal intensity, restricted diffusion, no enhancement, complex on CISS/FIESTA.
- Treatment
- Surgical resection, if symptomatic.
