We report the case of a 15-year-old young man who presented with disequilibrium and leftward spontaneous nystagmus. Since the video head impulse test at the initial visit showed right lateral semicircular canal hypofunction, the patient was suspected as having peripheral vertigo due to right semicircular canal hypofunction. However, his clinical course was considered as being atypical for peripheral vertigo caused by right semicircular canal hypofunction because of his small center of gravity sway, a negative Romberg’s phenomenon. Balance testing showed failure of visual suppression of caloric nystagmus, and insufficient optokinetic nystagmus responses, suggestive of central vestibular dysfunction. Contrast-enhanced brain MR imaging showed a neoplastic lesion with contrast effect occupying the region from the right middle cranial fossa to the cerebellopontine angle, with extension into the internal auditory canal. In addition, edematous changes due to compression by the neoplastic lesion were observed in the right midbrain, pons, and cerebellum. We diagnosed radiation-induced meningioma based on the histopathology and history of radiotherapy that the patient had received for acute lymphocytic leukemia. The central disequilibrium was diagnosed as being caused by compression of the cerebellum and brainstem due to radiation-induced meningioma arising from the cerebellopontine angle. In patients with a history of having received intracranial radiation in childhood, the possibility of occurrence of central disequilibrium caused by a radiation-induced brain tumor, which is a frequent complication, should be borne in mind.
