Abstract 460: Variation Of Bowhunter's Syndrome: Right Vertebral Artery Occlusion From Cervical Disc Herniation ‐ A Case Report
Authors: Cheema H. , Giurgiutiu D. 
Published: January 2025

Introduction
Bowhunter's syndrome (BHS) occurs when an individual turns their head, often greater than 45 degrees, causing mechanical occlusion of the ipsilateral vertebral artery (VA). Common causes include osteophytes or disc herniations [1]. This dynamic stenosis results in symptoms of vertebrobasilar insufficiency (VBI) such as vertigo, nystagmus, dizziness, and changes in vision and gait [3]. BHS is a rare but curable cause of VBI.

Methods/Case Presentation
A 59‐year‐old woman with a history of congestive heart failure, hypertension, obstructive sleep apnea, cervical spondylosis, thoracic spondylosis, atherosclerotic cardiovascular disease, hyperlipidemia, and type 2 diabetes mellitus presented with recurrent presyncope, vertigo, and progressive right upper and lower extremity weakness. Her symptoms worsened with head rotation to the right. Cerebral angiogram showed chronic occlusion of the left VA and rotational occlusion of the V2 segment of the right VA, which had 50% baseline occlusion and 80% occlusion with head turned to the right. The stenosis occurred greatest at C3‐4 due to a lateral cervical disc herniation. The patient possessed a small right posterior communicating artery and lacked collateral flow from the left VA.

Results
She was treated with a C3‐4 anterior cervical discectomy and fusion (ACDF) and skeletonization of right VA with resolution of positional occlusion of the VA. Postoperatively, her dizziness and instability resolved, but she experienced new dysphagia and operative site discomfort. Right extremity weakness persisted with 4/5 muscle strength in the right deltoid, bicep, tricep, wrist extension, grasp, and iliopsoas. Postoperative x‐rays showed good positioning of her C3‐4 interbody graft, anterior cervical plate, and screws. Two months later, a follow‐up cerebral angiogram confirmed resolution of right VA stenosis in all head positions.

Conclusion
This case provides insights into alternative presentations of BHS. Notably, the right VA was the primary symptomatic vessel, whereas the left VA is historically more affected [2]. More common causes like cervical spine trauma, neoplastic growths, and osteophytes may present with a larger constellation of symptoms that delay diagnosis [4].
A key takeaway is the body's adaptation to changes in head and neck perfusion. In healthy individuals, the contralateral VA compensates for posterior circulation demands [3]. This patient showed a combination of contralateral VA atherosclerosis and a lack of protective collateralization.
Conservative management is effective for approximately 75‐90% of cervical spine disc herniations, but the risk of cerebrovascular complications in this patient necessitated surgical intervention [5]. The anterior approach to discectomy has shown better outcomes compared to posterior decompression, with fewer instances of VA injury [6]. Vertebral stenting is an alternative that has historically shown success [7]. However, the risk of stent deformation and fracture in the cervical spine was considered too great. Her persistent right extremity weakness suggests possible secondary etiology or lasting deficits from transient cerebral hypoperfusion.
As with any cause of VBI, BHS should be considered as a risk factor for severe cerebrovascular events. This case continues to support digital subtraction angiograms for diagnosis and ACDF for surgical treatment as a successful pathway for those with BHS [6].