Unilateral paralysis of the hypoglossal nerve leads to deviation of the tongue to one side and atrophy. We report a case of metastatic brain tumor that was found by paralysis of the hypoglossal nerve. An 80-year-old woman visited our hospital with a complaint of disturbance of tongue movement. The tongue deviated towards the left side on protrusion and paralysis of the hypoglossal nerve was suspected. We introduced the patient to the department of neuropathic internal medicine of a hospital, because she had previously received treatment for lung adenocarcinoma there. The MRI examination revealed metastasis of tumors in the brain stem, pons, and cerebrum, one of which displaced the left hypoglossal canal. The patient was finally given a diagnosis of metastatic brain tumor-related hypoglossal paralysis. Cancer patients with neurologic manifestation in the oral cavity should be subjected to general examination to detect metastatic brain tumors.
