[A case of intracranial hypoglossal neurinoma with no preoperative hypoglossal nerve palsy].

A case of intracranial hypoglossal neurinoma without hypoglossal nerve palsy is reported. A 43-year-old housewife was admitted to our hospital with vertigo and left occipital headache. Neurologically, no cranial nerve deficits were present. CT scan and cerebral angiography showed a mass in the lower left posterior fossa. MRI also revealed a well circumscribed extra-axial mass compressing brain stem and cerebellum to the right. Left suboccipital craniotomy was performed and the tumor was removed subtotally. From the operative findings, the 8th to 11th cranial nerves were not related to the tumor, however, the origin of the tumor was not confirmed. The histology showed Antoni A type neurinoma mixed partially with Antoni B type. After the operation, the tongue deviation appeared to the left, but no other cranial nerve deficit was noticed. Post-operative neuroradiological reexaminations defined slight enlargement of the hypoglossal canal. Then, we concluded that the origin of the tumor must have been the hypoglossal nerve. Most intracranial hypoglossal neurinoma grow in the hypoglossal canal followed by enlargement or erosion of the hypoglossal canal. The author thought that this case suggests that this hypoglossal neurinoma originated from a few rootlets of hypoglossal nerve and grew mainly between the medulla and the hypoglossal canal.