Bow hunter's syndrome revisited: 2 new cases and literature review of 124 cases.

Rotational occlusion of the vertebral artery (VA), or bow hunter's syndrome, is a rare yet surgically treatable cause of vertebrobasilar insufficiency. The underlying pathology is dynamic stenosis of the VA by osteophytes, fibrous bands, or lateral disc herniation with neck rotation or extension. The authors present 2 previously unreported cases of bow hunter's syndrome and summarize 124 cases identified in a literature review. Both patients in the new cases were treated by VA decompression and fusion of the subaxial spine. Each had > 50% occlusion of the left VA at the point of entry into the transverse foramen with a contralateral VA that ended in the posterior inferior cerebellar artery. Analyzing data from 126 cases (the 2 new cases in addition to the previously published 124), the authors report that stenosis was noted within V1 in 4% of cases, in V2 in 58%, in V3 in 36%, and distal to C-1 in 2%. Patients presented in the 5th to 7th decade of life and were more often male than female. The stenotic area was decompressed in 85 (73%) of the 116 patients for whom the type of treatment was reported (V1, 4 [80%] of 5; V2, 52 [83%] of 63; V3/V4, 29 [60%] of 48). Less commonly, fusion or combined decompression and fusion was used (V2, 7 [11%] of 63; V3/V4, 14 [29%] of 48). Most patients reported complete resolution of symptoms. The authors conclude that patients with bow hunter's syndrome classically have an impaired collateral blood flow to the brainstem. This condition carries an excellent prognosis with decompression, fusion, or combined surgery, and individual patient characteristics should guide the choice of therapy.