[A case of dumbbell-shaped hypoglossal neurinoma]

The authors report a case of dumbbell-shaped hypoglossal neurinoma. A 46-year-old female was admitted to our clinic with a history of right hemiatrophy of the tongue for more than 10 years and bilateral paresthesia on the face and legs for half a year. Neurological findings on admission were right hypoglossal palsy, attenuation of right gag and palatal reflex, mild truncal ataxia, right Bruns nystagmus, bilateral paresthesia on the face and legs (left > right), bilateral hyper-reflexia on the extremities. No sign of increased intracranial pressure was noted. Conventional computed tomography demonstrated the bone destruction around the right hypoglossal canal, and three-demensional computed tomography clearly revealed the extent of the bone destruction. Magnetic resonance imaging showed a large dumbbell-shaped mass extending both intra-and extra-cranially through the right hypoglossal canal, which severely compressed the brainstem postero-medially. Right suboccipital craniotomy with C1 laminectomy was performed in the prone position, and the occipital bone was drilled far-laterally around the Foramen Magnum with right occipital condyle rongeured to expose the intracanallicular mass. The mass was totally removed except around the IX Xth cranial nerves near the jugular foramen. Hypoglossal neurinoma is rare, and our case is the 62nd case, and the 15th dumbbell-shaped case in the literature. Hypoglossal nerve palsy is characteristic in dumbbell-shaped hypoglossal neurinoma. Enlargement of the hypoglossal canal can be detected by conventional and three-dimensional CT. MRI is more effective than CT in revealing the mass. Total removal of the dumbbell-shaped tumor requires that the hypoglossal canal can be exposed sufficiently.(ABSTRACT TRUNCATED AT 250 WORDS)