Trochlear Schwannoma Presenting with Isolated Trigeminal Neuralgia.

BACKGROUND: Schwannomas arising from the cranial nerves controlling extraocular eye movements are very rare and usually present with some degree of diplopia.

CASE PRESENTATION: We report a 50-year-old woman who presented with isolated left-sided trigeminal neuralgia of 6 months' duration. Imaging demonstrated a homogeneously enhancing mass in the left ambient cistern, and the patient was brought to the operating room for resection. A retrosigmoid approach was used, and the mass was directly visualized arising from the trochlear nerve and compressing the dorsal root entry zone of the trigeminal nerve. A gross total resection of the mass was achieved, and microvascular decompression of the trigeminal nerve was performed. The tumor was pathologically confirmed as a schwannoma. At 3-month follow-up, the patient's facial pain was resolved, and her extraocular eye movements were intact.

CONCLUSIONS: A total of 32 pathology-confirmed cases of trochlear schwannoma have been previously reported in the English-language literature. Most of these tumors arose from the cisternal segment of the nerve, and most patients presented with frank trochlear nerve palsy on exam. We report the first case of trochlear schwannoma presenting with isolated trigeminal neuralgia.