Epidermoid cyst - cerebellopontine angle

Case contributed by Ammar Haouimi
Diagnosis almost certain


Right trigeminal neuralgia.

Patient Data

Age: 30 years
Gender: Female

Extra-axial mass at the right cerebellopontine angle, extending into the ipsilateral internal auditory canal (ICA), encasing the facial/vestibulocochlear nerves, and compressing the cisternal portion of the ipsilateral trigeminal nerve. It elicits a low signal on T1, heterogeneous signal on FLAIR and high signal on T2 with restricted diffusion and no enhancement seen on the postcontrast sequence.

Case Discussion

MRI features most consistent with a cerebellopontine angle epidermoid cyst extending into the ipsilateral internal auditory canal and compressing the trigeminal nerve.

DWI is important to differentiate an epidermoid cyst from an arachnoid cyst (the arachnoid cyst follows the CSF signal on all sequences with no restricted diffusion).

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