Bow Hunter Syndrome: An Illustrative Case and Operative Management

The differential for vertebrobasilar insufficiency is wide and can be caused by posterior circulation infarcts, steal-type phenomena, or other systemic causes. In the absence of imaging findings explaining symptomology, the utility of appropriate history gathering and dynamic angiography cannot be understated in identifying Bow Hunter's syndrome, a rare cause of dynamic vertebrobasilar insufficiency. We present a case of a 69-year-old man who complained of presyncope and severe dizziness when turning his head towards the right. On examination he had no radiculopathy but did have objective evidence of myelopathy. Computed tomography imaging and dynamic angiography demonstrated C3-C4 right uncovertebral joint hypertrophy and near complete stenosis of the right vertebral artery with dynamic head position towards the right. Given vertebrobasilar insufficiency and myelopathy, he was taken to the operating room for C3-C4 anterior cervical discectomy and fusion with vertebral artery decompression (Video 1). The patient provided consent for the procedure. Standard anterior cervical neck dissection was undertaken with additional platysmal undermining to facilitate exposure of the right uncovertebral joint and transverse processes. The vertebral artery was first decompressed above and below the area of most significant stenosis at the respective transverse foramina before the hypertrophied uncovertebral joint was removed. Next, discectomy and posterior osteophyte removal were completed in typical fashion followed by graft, plate, and screw placement. Postoperatively the patient had immediate resolution of symptoms and continued so at eight month follow-up. Imaging demonstrated return to normal caliber of the right vertebral artery and successful decompression.

Diagnosis and management of bow hunter's syndrome: 15-year experience at barrow neurological institute

BACKGROUND

Bow hunter's syndrome is a rare vascular phenomenon characterized by insufficiency of the posterior cerebral circulation induced by rotation of the head within normal physiologic range. The neurosurgical literature on evidence-based diagnosis and management of the disease is scarce, and reports are largely limited to case studies.

METHODS

A retrospective chart review was performed on all patients referred to Barrow Neurological Institute during the period 1999-2013 with signs and symptoms that were possibly indicative of bow hunter's syndrome. Demographic data from patient charts were collected, and the patients' imaging studies were reviewed.

RESULTS

There were 14 patients referred to Barrow Neurological Institute with symptoms concerning for bow hunter's syndrome, and 11 of these patients were confirmed to have dynamic vertebral artery compression on angiography. The location of compression was centered on C1-2 (50%) or C5-7 (50%). The compressed vertebral artery was typically the left artery (72.7%), and in 54.5% of cases, rotation of the head to the contralateral side produced symptomatic dynamic compression. Surgical decompression, via either an anterior (44.4%) or a posterior (55.6%) approach, was eventually performed in 9 patients. Decompression alone was performed in all cases; however, 1 patient developed cervical instability requiring an anterior cervical instrumented fusion 5 years later.

CONCLUSIONS

Decompression without fusion is a safe, reliable surgical option in patients with bow hunter's syndrome. Decompression is performed via a posterior approach for atlantoaxial vertebral artery compression and via an anterior approach for subaxial compression. Long-term complications include cervical instability, which may necessitate internal fixation and fusion.