Abducens nerve schwannoma: a case report and literature review

INTRODUCTION. Abducens nerve schwannoma are an extremely rare neurosurgical pathology. The peculiarity of these tumors is diagnostic difficulties at the preoperative stage, as often the neoplasms mimic schwannoma of the Gasser’s ganglion. Often persisting oculomotor disorders after surgery remain an unsolved problem.

CASE REPORT. We report a rare observation of such a tumor. A 38-year-old man presented with complaints characteristic of a left cerebellopontine angle lesion. Magnetic resonance imaging showed the presence of a dumbbell-shaped tumor with near the brainstem and parasellar nodes; its radiological characteristics were typical schwannoma of the Gasser’s ganglion. Intraoperatively, a left abducens nerve schwannoma destroying Dorello’s canal was verified, and the integrity of the nerve was anatomically disrupted by the tumor. Morphologic examination confirmed the diagnosis of schwannoma. Before surgery, the patient had paresis of the left abducens nerve, facial musculature dysfunction, and pyramidal insufficiency; after surgery, paralysis of the abducens nerve and some increase in hemiparesis were observed.

CONCLUSION. Clinical features and neuro-radiologic signs are often insufficient to make an accurate preoperative diagnosis. The source of the growth (the diverting nerve) can be suspected by careful history taking, when abducens nerve insufficiency appears before other symptoms, which are much more severe in the prime of the disease. The diagnosis of “abducens nerve schwannoma” is established intraoperatively and confirmed by pathomorphologic examination. It is necessary to emphasize the importance of the earliest possible diagnosis of this pathology, careful collection of anamnesis and timely neuroimaging examination in order to improve the results of treatment and prevent the appearance of gross oculomotor disorders after surgery.

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