The structures supplied by the anterior vestibular artery (lateral and anterior SCC and utricle) have the least collateral supply, making them most susceptible to ischemia. This is probably the reason that vertigo without hearing loss is commonly the TIA associated with AICA distribution ischemia. Note that the AICA also supplies the cerebellar flocculus in the cerebello-pontine angle (and hence if occluded can lead to a gaze-evoked nystagmus). More proximal branches of AICA supply the anterolateral portions of the pons (V, VII, VIII nuclei) and the middle cerebellar peduncle. Hence ipsilateral facial weakness, facial anesthesia and ataxia are also (in addition to hearing and vestibular disturbances) associated with occlusion of the AICA at its origin. When the IAA arises directly from the basilar artery a nearly pure peripheral vestibular cochlear syndrome can ensue with the exception that a gaze-evoked nystagmus may be superimposed due to involvement of the cerebellar flocculus.