A case of bow hunter's stroke caused by non-dominant vertebral artery.

Rotational movements in the territory of vertebrobasilar artery of the head and neck can induce vertebrobasilar insufficiency (VBI) or infarction. The term "bow hunter's stroke" or "rotational VBI" has been used to describe this clinical syndrome. In most cases, symptoms were provoked because of involvement of a dominant vertebral artery (VA) with hypoplasia or occlusion of the contralateral VA. The author presented a case in which bow hunter's stroke was caused by occlusion of a non-dominant VA ending in the posterior inferior cerebellar artery (PICA). Diagnosis of rotational VBI was based on stereotypical clinical symptoms related to head rotation and hemodynamic study of the effects of head rotation. VA compression was documented in dynamic ultrasonography including the disappearance of end-diastolic flow in extracranial portion of VA and marked reduction in blood flow velocity (more than 50%) in the intracranial portion of VA upon head rotation. We emphasize that rotational occlusion of this anatomical variation is an important cause of VBI. This may cause permanent neurological deficits if left undiagnosed.