[The special case: isolated neurinoma of the labyrinth (author's transl)].

A 28-year-old patient developed severe unilateral sensorineural deafness and vertigo. A tumor of the cerebello-pontine angle was assumed on the basis of a computed tomogram, and a translabyrinthine exposure of the internal auditory canal was performed. A histologically verified neurinoma was found, but in the labyrinthine vestibule. Although the tumor extended into the horizontal semicircular canal, both the internal auditory canal and the cerebello-pontine angle were tumor-free. The labyrinthine origin of a neurinoma has relevant implications for the differential diagnosis of progressive sensorineural deafness. As such, the filling of the internal auditory canal with contrast media does not preclude the presence of a tumor at the eighth nerve and requires additional precision tomography of the labyrinth.