Case 1

This is an MRI brain study showing an extra-axial lesion within the right cerebello-pontine angle cistern – it appears to be insinuating into and expanding the cistern and exerting slight mass effect on the adjacent pons and cerebellar peduncle. The lesion is hyperintense on the T2 images – as hyperintense as CSF. On the 3D SPGR images, the lesion shows heterogeneous signal intensity with some intermediate signal contents. The lesion shows high SI on the DWI series with corresponding low ADC values – this indicates restricted diffusion.

These radiological features are highly suggestive of an intracranial epidermoid cyst. Next I would rule out dermoid cyst as a differential by looking at a T1 / T1 fatsat series to assess for presence (or absence) of fat. I would also rule out a solid neoplasm such as an acoustic neuroma by obtaining a gadolinium enhanced series, as epidermoid cysts should not show any enhancement.