Ocular torsion associated with infarction in the territory of the anterior inferior cerebellar artery: Frequency, pattern, and a major determinant

BackgroundAcute ischemic stroke in the distribution of the anterior inferior cerebellar artery (AICA) can cause the vestibular dysfunction in the roll plane of the vestibuloocular reflex with abnormal ocular torsion (OT). There has been no systemic study that carefully investigates the nature of OT that occurs with AICA infarction.ObjectivesTo investigate the frequency, the characteristic patterns of OT associated with AICA territory infarction, and the crucial site for determining the direction of OT in AICA territory infarction.MethodsWe studied 12 consecutive cases of infarction in the territory of the AICA diagnosed by brain MRI. Fundus photography, prism cover test, and subjective visual vertical tilting test were performed to evaluate the function of the otolith system. Pure tone audiogram was also performed to evaluate the function of the auditory system.ResultsNine (75%) of 12 patients exhibited pathological ocular torsion (OT). Two types of pathological OT were found: ipsiversive OT accompanying skew deviation (n = 6), and contraversive OT only (n = 3). Six patients with ipsiversive OT with skew deviation showed an audiovestibular loss with canal paresis and hearing loss ipsilaterally whereas three patients with contraversive OT without skew deviation had a normal audiovestibular response. In all cases with pathological OT, the direction of the subjective visual vertical tilt corresponded to the direction of the OT.ConclusionsOur findings emphasize that the peripheral vestibular structure with inner ear probably plays a crucial role in determining the direction of OT associated with AICA territory infarction.