Simultaneous Bilateral Vertebral Artery Occlusion in the Lower Cervical Spine Manifesting as Bow Hunter's Syndrome -Case Report-

Abstract

A 59-year-old male had suffered near-syncopal episodes for more than one year that occurred immediately on turning his head to the left. Cerebral magnetic resonance (MR) imaging did not detect any contributing lesions with well-developed posterior communicating arteries. Dynamic radiography of the cervical spine showed mild instability at C5-6 and concomitant intramedullary hyperintensity confirmed by T 2 -weighted MR imaging. Cervical computed tomography demonstrated an osseous protrusion in the right foramen transversarium at C5. Dynamic cerebral angiography revealed simultaneous vertebral artery (VA) occlusion at C6 on the right and C5 on the left associated with leftward head rotation. The VA showed an intact course at the C1 to C2 levels. The patient underwent anterior fusion followed by decompressive foraminotomy at C5-6 and C6-7 and meticulous resection of the markedly thickened fibroligamentous structure which was considered to contribute to the rotational VA occlusion. Postoperatively he no longer suffered near-syncope during head rotation. Bow hunter's syndrome is an infrequent type of vertebrobasilar insufficiency that may need surgical management for potential threat of ischemic stroke. Simultaneous VA occlusion at the lower cervical level can cause bow hunter's syndrome. Dynamic cerebral angiography is a useful modality for evaluating bow hunter's syndrome even if the patient cannot tolerate dynamic examination for the immediate symptom. Accurate anatomical knowledge of the uncovertebral foraminal region combined with intraoperative dynamic study is essential for safe surgery to the VA and favorable outcome.

Rotational Vertebral Artery Occlusion

“…[1][2][3] Most patients with RVAO exhibit a stenosis or anomaly (eg, hypoplasia or termination in the posterior inferior cerebellar artery) of the vertebral artery (VA) on 1 side and the dominant VA is compressed at the C1-2 level during contraversive head rotation, which compromises the blood flow in the vertebrobasilar artery territory (typical RVAO; Figure 1). [3][4][5] However, some patients may show atypical patterns, such as compression of VA at other cervical levels, [6][7][8][9][10][11] simultaneous compression of both VAs, 2,[12][13][14][15] compression of the dominant VA during ipsilateral head rotation or tilt, 6,7,10,11,16 and compression of the nondominant VA terminating in the posterior inferior cerebellar artery (PICA). [17][18][19] Based on the side of tinnitus and patterns of nystagmus induced by head rotation, transient excitation of the inner ear in the compressed VA side has been proposed as a mechanism of vertigo and nystagmus in RVAO.…”

Bow hunter’s stroke due to instability at the uncovertebral C3/4 joint

“…Therefore, to address this problem, anterior discectomy and fusion were performed. There were several reports in which anterior discectomy and fusion with decompression of the VA were performed for bow hunter's stroke [10,11,19]. However, in the present case, because there was no evidence of osteophytic change or cervical disc herniation, compression of the VA by this mechanism seems less likely.…”

“…Anticoagulation may alleviate symptoms [5,7], but it is only palliative and does not directly treat the underlying pathology [4,5,11,17,18]. Surgery is an option for patients who fail to respond to conservative therapy [18].…”

“…In most cases, the dominant VA is occluded at the atlanto-axial level and coexisted contralateral hypoplastic VA or poor collateral flow supplied by the anterior cerebral circulation via the posterior communicating artery contributes to this vertebrobasilar insufficiency [2,[4][5][6][7][8]. The extrinsic factors identified VA compression by osteophyte, cervical spondylosis, fibrous bands, cervical disc herniation, or VA stretching by intervertebral instability along the craniocervical axis [3,[7][8][9][10][11][12].…”

Advances in the Pathogenesis, Diagnosis and Treatment of Bow Hunter's Syndrome: A Comprehensive Review of the Literature

“…The symptoms usually resolve immediately as the head returns to a neutral position. The threshold angles that evoke the symptoms are 30° [25], 40° [40], 45° [15,29,33,41,42,43], 60° [13,19,42,44], 80° [45] and 90° [46]. Velat et al [30] summarized in their paper that classic presentations of this syndrome included dizziness, vertigo, nystagmus, nausea with associated emesis, Horner's syndrome, syncope, and motor or sensory deficits that occur with head rotation (relatively rare in BHS).…”