Schwannoma arising from the intermediate nerve and manifesting as hemifacial spasm. Case report.

This 35-year-old man presented with left facial spasm that had persisted for 10 months. Microvascular decompression was performed to relieve the symptom. No responsible vessel could be identified during surgery, but a small mass seeming to arise from the intermediate nerve and compressing the seventh cranial nerve was removed. The histological diagnosis was Antoni-B type schwannoma. This unique case of schwannoma arising from the intermediate nerve was recognized by means of an operative microscope, and supports the idea that portions of the seventh nerve schwannoma originate from the components of the intermediate nerve.