Abducens nerve schwannoma: case report and review of the literature

Schwannomas of the abducens nerve are extremely rare. The authors report a case with this tumor and discuss its clinical and radiographic characteristics. A 36-year-old man presented with 6-month history of diplopia. Right abducens nerve paresis was noted on neurologic examination. Magnetic resonance imaging revealed a 4-cm sized heterogeneously enhancing mass in the right cerebellopontine angle. Although schwannoma was suggested, no direct radiographic evidences regarding its origin were identified. Instead, the facial and vestibulocochlear nerve complex was found to be displaced posteriorly by the tumor on MR three-dimensional T2-weighted driven equilibrium sequence. Resection of the tumor was carried out via retrosigmoid approach. As the encapsulated partially suckable yellowish tumor was debulked and dissected, the abducens nerve was found to fan along and be attached to the medial surface of the tumor, which was cut at this point. Complete excision of the tumor was accomplished, and reanimation of the nerve was done by end-to-end anastomosis. Histologic feature was typical of schwannoma. Abducens schwannoma, although rare, should be taken into account for differential diagnosis of the cerebellopontine angle tumors. Appreciation of the characteristic clinical and radiographic features may provide an accurate preoperative diagnosis.