Background: Lower cranial nerve schwannomas are rare and only 63 cases originating from the accessory nerve have been documented.
Case Description: We report a 61-year-old man who presented with a 3-month history of dysmetria, ataxic gait, and frequent falls. Magnetic resonance imaging revealed a giant rim-enhancing cystic lesion at the right cerebellomedullary cistern, which markedly displaced the brainstem and caused a critical compression on surrounding structures and mild hydrocephalus.