Abstract Number ‐ 76: Bow hunter’s syndrome‐ a rare case of hearing loss associated with co‐dominant vertebral artery compression

Abstract

Introduction Bow hunter’s syndrome (BHS), also known as rotational vertebral artery syndrome, refers to symptomatic vertebrobasilar insufficiency (VBI) caused by mechanical compression and severe stenosis or occlusion of the vertebral artery (VA) during neck and head rotation. Etiologies include bony spurs and osteophytes, or hypertrophic muscles and ligaments compressing typically on the dominant vertebral artery. Upon turning their head, patients experience posterior circulation symptoms such as vertigo, dizziness, syncope, nausea, tinnitus, or headache. These patients are at risk of stroke due to repetitive mechanical damage to the vessel and thromboembolism. [1] We present a rare case of BHS associated with hearing loss that was caused by bony spurs compressing on a left co‐dominant vertebral artery seen on turning head to both sides. Methods A woman in her 50s presented with sporadic progressive episodes of dizziness which started about 4 years. In addition, she reported experiencing episodic tinnitus in her left ear, frequent headaches, neck pain, and syncopal episodes. She was diagnosed with severe left ear sensorineural hearing loss (SNHL). Vestibular therapy and multiple neuropathic medications (nortriptyline, gabapentin) only provided her with minimal relief. Results Examination showed left SNHL and neck tenderness. X‐ray of cervical spine showed bony hypertrophy adjacent to the dens and inferior to the anterior arch of C1, suggestive of large osteoarthritic bony spurs. CT angiogram showed narrowing of the left vertebral artery at C1 due to severe hypertrophic arthropathy of the lateral mass articulation. It also showed impingement of the left VA in the left transverse foramen. The intradural portion of the VA (V4) appeared to be co‐dominant with normal size. Dynamic cerebral angiogram revealed near occlusion of the left VA at the level of C1‐C2 with head to the right. Left VA remained patent in neutral position, and experienced reduction in flow with head rotation to the left. The dynamic stenosis of VA caused by mechanical compression upon head turn leading to VBI, and reversal of stenosis when rotating head to neutral position was consistent with diagnosis of Bow hunters syndrome. Conclusions This case report highlights a rare presentation of VBI caused by dynamic stenosis of VA as a sequela of mechanical compression of a co‐dominant VA upon head turn to both sides. Only about 2% of the BHS patients experience symptoms during head turn to both sides [2], which was the finding in our patient. Furthermore, this case illustrates an association between BHS and SNHL. Hearing loss is previously described in vertebral artery atresia [3]; however, we present a novel association between acquired BHS and SNHL. Although we could not prove the causality, the coexistence of the two conditions in this patient may help to elicit further clinical consideration and evaluation in patients with SNHL of unknown etiology.