Abducens Nerve Schwannoma: Case Report and Review of Literature

Introduction: Schwannomas of the abducens nerve are extremely rare tumors affecting cavernous, cisternal, or both segments of the sixth cranial nerve. These tumors were described only in 17 cases. Clinical features and neuroradiological imaging are frequently insufficient to reach an accurate preoperative diagnosis.

Material: A 60-year-old man presented with vertigo, falls, headache, and post-traumatic severe hearing deficit on the left side, but without any symptoms and signs of sixth nerve palsy. Magnetic resonance imaging showed cystic lesion in the right anterolateral mesencephalon-pontine junction.

Method: Radical surgery, performed via a right anterior transpetrosal approach with electrophysiological monitoring, demonstrated an extrinsic tumor originating from the prepontine portion of the sixth nerve with severe mesencephalon and pons compression. Histological examination was consistent with diagnosis of schwannoma. Postoperatively, the patient had a complete right abducens nerve palsy associated with severe diplopia and quickly improving slight left-sided hemiparesis. After 9 months, the sixth nerve palsy completely disappeared without any residual diplopia. The serviceable hearing on the right side was preserved without deterioration. Postoperative magnetic resonance imaging confirmed the radical resection.

Conclusion: The correct diagnosis of abducens nerve schwannoma is established by intraoperative observation of tumor attachment to the sixth nerve and by histopathological analysis. Radical resection of these rare abducens schwannomas in the prepontine area can be performed via an individually selected microsurgical approach without any neurological deterioration, including the abducens nerve function.