Bow hunter syndrome

CMAJ | November 7, 2022 | Volume 194 | Issue 43 © 2022 CMA Impact Inc. or its licensors A 59-year-old man presented to our neuroendovascular clinic with a 10-month history of chronic dizziness, described as a spinning sensation, with associated gait instability and blurred vision upon head rotation. On examination, the spinning sensation could be elicited with mostly leftward head rotation. When the patient turned his head to a more neutral position, the symptoms slowly subsided. Flexion or extension of the neck did not elicit vertigo. The Dix–Hallpike manoeuvre did not elicit nystagmus and a Romberg test was negative. We did not observe any other neurologic abnormalities. We initially thought the patient had benign paroxysmal positional vertigo; however, the Epley manoeuvres, vestibular rehabilitation therapy and meclizine were ineffective. Given the refractory nature of the patient’s vertigo, lack of a clear diagnosis and persistent ability to elicit symptoms with head rotation, we ordered cerebral angiography, which showed focal 80% narrowing of the left vertebral artery with a leftward head turn (Figure 1). We diagnosed bow hunter syndrome (BHS) and referred the patient to a neuro surgeon for an anterior cervical discectomy and removal of the uncinate process and associated osteophyte, which was compressing the left vertebral artery. At 3 months postsurgery, the patient described no rotational vertigo with only residual dizziness, which was gradually improving. Bow hunter syndrome is also called rotational vertebral artery occlusion syndrome.1,2 Patients usually present with reproducible, transient vertigo when they rotate or extend their head owing to dynamic stenosis of the affected vertebral artery (most often caused by an osteophyte, less often by disc herniations or tumours).2 The incidence of BHS is not known and there are no guidelines on diagnosis and management. Imaging to diagnose BHS includes computed tomography angiography, magnetic resonance angiography and cerebral angiography.1,3 Some patients can be managed nonoperatively, whereas others benefit from surgery, which appears to have a good prognosis.3