Isolated trigeminal nerve sarcoid granuloma mimicking trigeminal schwannoma: case report.

OBJECTIVE AND IMPORTANCE: Sarcoidosis most commonly presents as a systemic disorder. Infrequently, sarcoidosis can manifest itself in the central nervous system, with granulomas involving the leptomeninges and presenting with facial nerve weakness. Sarcoid of the trigeminal nerve is exceedingly rare and can mimic trigeminal schwannoma. We review the literature on sarcoid granulomas of the trigeminal nerve and compare their radiological features with the more common schwannoma.

CLINICAL PRESENTATION: A 33-year-old woman presented with a history of left-sided facial pain and numbness for 11 months, which was presumed to be trigeminal neuralgia. A trial of carbamazepine had been unsuccessful in relieving the facial pain. Her neurological examination revealed decreased facial sensation in the V(1)-V(2) distribution. Preoperative magnetic resonance imaging demonstrated a contrast-enhancing mass centered in the left cavernous sinus with extension along the cisternal portion of the left trigeminal nerve.

INTERVENTION: The patient underwent a left frontotemporal orbitozygomatic craniotomy with intraoperative neurophysiological monitoring of Cranial Nerves III, V, and VI and image guidance for subtotal microsurgical resection of what appeared, grossly and on frozen section, to be a neurofibroma. The final pathology report, however, revealed a sarcoid granuloma of the trigeminal nerve.

CONCLUSION: The differential diagnosis of contrast-enhancing lesions in the lateral wall of the cavernous sinus should include inflammatory conditions such as sarcoidosis. We recommend that surgery for biopsy or decompression be used only for those patients in whom a diagnosis cannot be confirmed with noninvasive testing. If surgery is performed, intraoperative frozen pathology is very useful in guiding the extent of resection.