A Case of Supralabyrinthine Petrous Bone Cholesteatoma Mimicking Facial Nerve Schwannoma

Abstract

We report the case of a 31-year-old woman with a supralabyrinthine petrous bone cholesteatoma who presented with acute facial paralysis, without other symptoms; she had first noticed the symptoms 2 months earlier. She was prescribed oral steroid therapy at a previous clinic, which had proved ineffective. Examination revealed a normal appearance of the tympanic membrane, and pure tone audiometry showed no evidence of hearing loss. Computed tomography (CT) revealed a spindle-shaped soft-tissue lesion occupying the labyrinthine segment of the facial nerve coursing to the epitympanum. Gadolinium-enhanced magnetic resonance imaging (MRI) revealed a non-enhancing mass in the same region. A provisional diagnosis of facial nerve schwannoma was made on clinical and radiological grounds, and surgical resection was performed via a middle fossa approach. Keratin debris was found along the labyrinthine segment of the facial nerve coursing to the ossicles, which led us to make the diagnosis of cholesteatoma. The lesion was completely resected along with the head of the malleus and incus by mastoidectomy, and ossiculoplasty was performed. Histological examination confirmed the diagnosis of cholesteatoma. The patient’s facial paralysis failed to recover. In patients with a small lesion in the petrous bone who present with isolated facial palsy as the only clinical manifestation, it is often difficult to differentiate between a cholesteatoma and facial nerve schwannoma, and gadolinium-enhanced MRI is a useful imaging examination to differentiate between the two diseases. In the present case, facial nerve schwannoma was suspected as the most likely diagnosis based on the clinical presentation and CT findings; however, the lack of enhancement on gadolinium MRI pointed to the diagnosis of cholesteatoma. Physicians should be aware of these clinical aspects for appropriate treatment planning.