Superior divisional vestibular paresis in anterior inferior cerebellar artery infarction.

A 74-year-old woman with sudden vertigo and dysarthria showed spontaneous nystagmus beating rightward, upward and clockwise. She also exhibited dysfunction of the left utricle and superior and horizontal canals, which was documented by head impulse and heave tests, measurements of ocular torsion and subjective visual vertical tilt, bithermal caloric tests, and rotation axis analysis of the spontaneous nystagmus. In contrast, functions of the left posterior canal, saccule, and cochlea were remained intact, as evidenced by normal head impulse test, audiometry and vestibular evoked myogenic potential. MRI revealed an acute infarction in the left lateral pons of anterior inferior cerebellar artery (AICA) territory. Our patient with AICA infarction showed isolated damage to the superior vestibular labyrinth or its afferents with preservation of the inferior vestibular labyrinth and auditory function. Our patient provides further evidence that isolated damage to the superior vestibular labyrinth or its afferents may be a mechanism of isolated vascular vertigo.