Bow hunter's syndrome after contralateral vertebral artery dissection.

Bow hunter's syndrome is characterized by transient vertebrobasilar insufficiency that is elicited by neck rotation. This syndrome is has various causes, such as osteophytes, tumors, fibrous bands, infection, and trauma. We report a unique case of bow hunter's syndrome. The patient visited our hospital because of left nuchal pain. A magnetic resonance imaging scan revealed left vertebral artery (VA) dissection, which was the cause of his nuchal pain. He began to feel faintness upon turning his neck to the left after left VA dissection. Digital subtraction angiography revealed that the right VA was fully patent in a neutral neck position, but focal stenosis appeared at the C2 vertebral level upon turning his head 60° to the left. This stenosis became complete occlusion at turning his head to the end of his range of motion. From these findings, a diagnosis of bow hunter's syndrome was made. Dissection of the contralateral (left) VA caused a failure in compensatory blood flow, resulting in bow hunter's syndrome. This represents the first report of bow hunter's syndrome occurring after onset of the contralateral VA dissection.