Cholesterol granuloma in facial nerve canal presenting with facial nerve paralysis.

Cholesterol granulomas (CGs) are frequently found in the temporal bone, but their presence in the facial nerve has not been reported. We report a case of a 58-year-old woman who presented with left facial palsy caused by a CG that appeared to have originated in the facial nerve. Temporal bone computed tomography (CT) revealed soft tissue masses in the left middle ear spaces, and the facial canal was dilated from the genu to the vertical portion. Magnetic resonance imaging (MRI) revealed high signal intensity on T1-weighted images and partially high signal intensity on T2-weighted images, although no significant enhancement was observed on gadolinium-enhanced MRI. Surgical findings revealed CG in the middle ear spaces, but the facial canal remained intact and lacked continuity with the internal mass. Histopathological analysis verified the mass as a CG accompanied by cholesterol crystals. The mass was located within and continuous with the epineurium. These findings indicate that hemorrhage in the facial canal may have triggered the formation of the CG, causing left facial palsy due to increased pressure in the facial canal.