Abducens nerve schwannoma: a case report and review of the literature.

Background: Schwannomas of the abducens nerve are extremely rare tumors; only 10 cases have been reported so far. The tumor may be located within the cavernous sinus (CS) or more commonly at the prepontine region. Patients usually present with VIth cranial nerve paresis.

Methods: We report a case of a 42-year-old male patient who presented with headache, vertigo, and hearing deficit, but no symptoms or signs related to a VIth cranial nerve impairment. Computed tomography and magnetic resonance imaging showed a large mass with a ring-like contrast enhancement in the prepontine area. Surgical treatment, via a simple retrosigmoid suboccipital approach, revealed a schwannoma originating from the VIth cranial nerve at its prepontine portion. Postoperative histological examination confirmed the diagnosis of schwannoma, and the patient had only a VIth cranial nerve palsy, which resolved during long-term follow-up.

Conclusions: Abducens schwannomas are rare tumors, representing less than 1% of all intracranial schwannomas in our clinic and about 13% of oculomotor nerve schwannomas reported in the literature. These lesions can be mainly divided into tumors originating from the intracavernous portion of the VIth cranial nerve or more commonly from the cisternal part of the nerve, leading to a lesion in the prepontine region. In such cases, with no invasion of the cavernous sinus, radical tumor resection with preservation of the abducens nerve can be performed via a simple suboccipital retrosigmoid approach.