What is Bow Hunter Syndrome?
Bow Hunter Syndrome (BHS) is a rare condition characterized by symptomatic vertebrobasilar insufficiency caused by mechanical occlusion or stenosis of the vertebral artery during head rotation or extension, resulting in transient neurological symptoms that resolve when the head returns to neutral position. 1
Clinical Presentation
Patients typically present with transient vertigo, dizziness, syncope or near-syncope, visual disturbances, tinnitus, and nausea that are triggered specifically by head rotation or extension. 1, 2, 3
Symptoms immediately resolve when the head is returned to neutral position, which is pathognomonic for this condition. 2, 4
In severe cases, patients may progress to posterior circulation stroke if the condition remains untreated. 1, 4
The syndrome should be considered in the differential diagnosis of recurrent ataxia in children, though it predominantly affects adults. 5
Underlying Pathophysiology
The mechanical compression occurs most commonly at the atlanto-axial level (C1-C2) or in the V2 segment (C2-C6) of the vertebral artery. 4, 6
Abnormal bony structures causing compression include osteophytes, disc herniation, cervical spondylosis, tendinous bands, or tumors. 1
The condition may be complicated by concurrent cerebrovascular disease including subclavian artery stenosis, carotid artery stenosis, or vertebral artery origin stenoses. 2
In rare cases, pseudoaneurysm formation at the V3 segment can occur as a complication. 3
Diagnostic Approach
Digital subtraction angiography with dynamic head rotation remains the gold standard for diagnosis. 1, 4
Dynamic angiography must be performed with the head in both neutral and rotated positions to demonstrate the mechanical occlusion. 4
CT angiography can identify concurrent stenoses of the subclavian, carotid, and vertebral arteries. 2
Doppler sonography, MRI, and MRA are widely used supplementary imaging modalities. 1
Look specifically for near-total occlusion of the vertebral artery as it exits the C2 foramen during provocative head positioning. 3
Treatment Algorithm
First-Line: Conservative Management
Initial conservative management should be attempted in symptomatic patients. 1, 2
This includes avoiding provocative head positions and physical therapy.
Second-Line: Surgical Intervention
When conservative management fails, posterior cervical fusion (typically C1-C2) with vertebral artery decompression is the primary surgical approach. 5, 4, 3
Tailored vertebral artery decompression with or without fusion provides excellent clinical and radiological results with low treatment-related morbidity. 4
Surgical techniques include bilateral C1 lateral mass screws and C2 translaminar screws with bilateral intrafacet cages to promote segmental fusion. 3
For patients with concurrent cerebrovascular disease, global revascularization via subclavian artery stenting and carotid endarterectomy may be considered before or instead of direct vertebral artery intervention. 2
Alternative: Endovascular Intervention
Vertebral artery stenting in the V2 segment (C2-C6) is a feasible, safe, and clinically effective minimally invasive alternative. 6
Stenting can be performed without significant technical difficulties and provides symptomatic relief with minimal residual stenosis on dynamic angiography. 6
This approach may be particularly useful in patients who are poor surgical candidates or prefer less invasive treatment. 6
Clinical Outcomes
Surgical decompression and fusion result in resolution of vertebrobasilar insufficiency symptoms with no neurological deficits postoperatively in most cases. 5, 3
Treatment-related morbidity is low with both surgical and endovascular approaches. 4, 6
All four patients treated with vertebral artery stenting in one series reported symptomatic relief. 6
Critical Pitfalls to Avoid
Do not dismiss transient positional symptoms as benign positional vertigo without considering BHS, especially if symptoms are consistently triggered by specific head positions. 4
Static imaging alone is insufficient—dynamic angiography with head rotation is essential to establish the diagnosis. 1, 4
Do not delay treatment in patients with recurrent symptoms, as progression to posterior circulation stroke can occur. 1, 4
When pseudoaneurysm is present, surgical stabilization of the affected segment is necessary to prevent catastrophic complications. 3