Rotational vertebral artery syndrome due to compression of nondominant vertebral artery terminating in posterior inferior cerebellar artery.

Rotational vertebral artery syndrome (RVAS) is characterized by recurrent attacks of paroxysmal vertigo, nystagmus, and ataxia induced by head rotation. We report on a patient who developed atypical RVAS due to compression of the vertebral artery (VA) terminating in the posterior inferior cerebellar artery (PICA). A 59-year-old man suffered from vertigo and nystagmus induced by leftward head rotation and oculography showed right beating horizontal-torsional and downbeat nystagmus. Cerebral angiography showed hypoplastic right VA terminating in PICA without connection to the basilar artery. The basilar artery received its flow from the left VA only and branched out both anterior inferior cerebellar arteries. Cerebral angiography revealed a complete occlusion of the right distal VA at the level of the C1-2 junction when the head was rotated to a leftward position. In contrast, the blood flow through the left vertebral and basilar arteries remained intact while turning the head to either side. The hemodynamic compromise observed in our patient with RVAS indicates that isolated vertigo and nystagmus may occur due to transient ischemia of the inferior cerebellum or lateral medulla.