[Intralabyrinthine schwannoma extending into the round window niche and internal auditory canal].

Intralabyrinthine schwannomas (ILSs) are rare benign neoplasms arising from distal branches of the cochlear, superior vestibular, or inferior vestibular nerves. We report on a case of ILS with extensions to the round window niche and internal auditory canal (IAC) in a 47-year-old male. The patient noticed sudden hearing loss and tinnitus in his left ear at the age of 36, received steroid therapies, but was left with complete deafness. He had suffered from repetitive vertigo attacks for 6 months at 41. At 46 when he presented with deterioration of his left tinnitus, he was finally diagnosed as having ILS on enhanced MRI and constructive interference in steady-state analysis. The tumor was located in all turns of cochlea, vestibule, and the fundus of the IAC. Because follow-up MRI suggested growth of the IAC tumor, we performed total removal of the tumor via the translabyrinthine and transcanal approaches. The tumor had invaded only the cochlear nerve in the IAC and appeared in the round window niche in the middle ear. Pathological examination showed an Antoni A type schwannoma with fibrous changes of the semicircular canals. We should remember this inner