Schwannoma of the intermediate nerve.

The intermediate nerve is seldom identified as the site of tumor origin in cerebellopontine angle schwannomas. A 29-year-old man presented with a 6-month history of slowly progressive hearing loss and dizziness; facial nerve weakness was not observed clinically. Magnetic resonance imaging revealed a tumor in the left cerebellopontine angle region extending up to the geniculate ganglion and along the course of the superficial petrosal nerve. A CT scan showed enlargement of the facial nerve canal. Microsurgery was performed via an extended retrosigmoid approach. Intraoperative and electrophysiological findings identified the intermediate nerve as the site of tumor origin.