Extended Retrosigmoid Craniotomy for Resection of an Abducens Schwannoma

Schwannomas arising from the abducens nerve are rare, comprising approximately 1% of intracranial schwannomas. Although cranial nerves subserving motor functionality are less prone to schwannoma development than are sensory cranial nerves, abducens schwannomas have been observed in both the sporadic and syndromic settings. Abducens schwannomas may arise from any segment of cranial nerve VI and are subdivided as cisternal, cavernous, or intraconal, the last of which is very rarely reported. Standard first-line treatments include microsurgery or stereotactic radiosurgery, with resection preferred for larger tumors associated with symptomatic mass effect, brainstem effacement, or hydrocephalus. Common presenting features include headaches and extraocular movement dysfunction, which has been reported to improve after surgery in approximately 50% of patients. We report a cisternal-segment abducens schwannoma treated with microsurgical resection in a woman who initially presented with back pain and leg weakness. Magnetic resonance imaging of the brain revealed an enhancing tumor in the prepontine cistern, and resection via extended retrosigmoid craniotomy was recommended. After a detailed discussion of the risks, benefits, and alternatives of observation, radiosurgery, and resection, the patient elected to proceed with the procedure. The tumor was noted to arise from the abducens nerve, and a near-total resection was achieved, with a small, adherent residuum left along the nerve to preserve its functional potential. The patient had transient postoperative ipsilateral cranial nerve VI palsy, which resolved during follow-up. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.