The Motor Branch of the Median Nerve, a Rare Localization of Schwannoma

Schwannoma is the most common benign tumor of peripheral nerve. Only 7% of schwannomas arise from the median nerve, and its localization in the motor branch is extremely rare. A 57-year old right-handed female presented with a carpal tunnel syndrome symptoms associated to a little painful thenar swelling in the left hand with no motor or sensory deficit. An electromyogram confirmed the clinical diagnosis of carpal tunnel syndrome. Ultrasonography (US), performed to study the thenar swelling, revealed an infracentimetric avascular well-limited intramuscular mass. Surgical resection of the mass was performed satisfactorily with preservation of nerve fascicles. Histopathology concluded to a benign schwannoma of the motor branch of the median nerve. In the literature reviewed by us, this is the third case of motor branch of the median nerve schwannoma.