Epidermoid Cyst with Torcular Herophili Obstruction and Unusual Venous Drainage.

Background: An epidermoid cyst arising from diploic space in the skull can cause an intracranial mass effect with compression of the underlying venous sinuses.

Case Description: A 66-year-old woman came to us with a persistent headache and unsteadiness. Computed tomography demonstrated an occipital bone cystic lesion with an intracranial mass effect overlying the torcular herophili, with high-intensity findings in diffusion-weighted magnetic resonance imaging. Cerebral angiogram demonstrated obstruction of the torcular herophili with development of diploic venous drainage. The patient underwent removal of the lesion and a cranioplasty procedure. The diagnosis was torcular epidermoid cyst. The postoperative course was uneventful, and the symptoms were resolved.

Conclusions: Development of diploic venous drainage contributed to avoidance of critical intracranial hypertension during slow growth of a torcular epidermoid cyst.