Bow hunter's syndrome due to an anomalous right vertebral artery origin and contralateral absence: a case report and literature review

Abstract

Background: Bow Hunter's syndrome (BHS), also known as rotational vertebral artery occlusion (RVAO), is a rare condition characterized by dynamic vertebrobasilar insufficiency due to position-dependent occlusion of the vertebral artery (VA). In the existing literature, most cases of BHS are attributed to osteophytic compression originating from the occipital condyle or within the transverse foramen, often accompanied by anatomical abnormalities of the VA. However, cases presenting solely with VA anomalies in the absence of any cervical vertebral structural abnormality are rare. This case report presents a unique instance of BHS in a 56-year-old male, attributed to the anomalous origin of the right VA and the absence of the left VA, without cervical structural abnormalities.

Case presentation: The patient exhibited symptoms like episodic dizziness and vertigo, which were exacerbated by rightward head rotation and alleviated upon returning to a neutral position. Diagnostic evaluation, including digital subtraction angiography, revealed that the right VA originated from the right common carotid artery and compression-induced stenosis of the right VA during head rotation. Conservative management, including avoidance of certain head movements and anti-arteriosclerosis medication, led to symptom resolution over a two-year follow-up period.

Conclusions: This report contributes to the understanding of BHS by highlighting a rare vascular anomaly presentation and incorporates a review of 14 similar case reports in the literature describing that an anatomical abnormality of the VA is mainly responsible for the pathology of BHS in the absence of cervical vertebral anomalies, thus emphasizing the need for careful diagnostic and management strategies.

Keywords: Absence of left vertebral artery; Bow hunter’s syndrome; Case report; Rotational vertebral artery occlusion; Vertebral artery anomalies.

Fig. 1

Magnetic resonance angiography (MRA) and computed tomography angiography (CTA) of the head and neck. Imaging reveals narrowing at the origin of the left subclavian artery and the absence of the left vertebral artery (VA). It also shows an aberrant right subclavian artery and the right VA originating from the right common carotid artery (A Anterior view of MRA, B Lateral view of MRA, C Anterior view of CTA, D Lateral view of CTA). Red arrows indicate the right internal jugular vein, yellow arrows indicate the right VA, green arrows indicate the left subclavian artery, and blue arrows indicate the aberrant right subclavian artery

Fig. 2

Digital subtraction angiography imaging. With the head in a neutral position, angiography of the vertebral artery (VA) shows no stenosis (A Anterior view; B Lateral view). When the head is turned to the right, angiography of the right VA reveals stenosis, during which the patient experiences dizziness and returns to a neutral position (C Anterior view; D Lateral view). Three-dimensional angiographic imaging of the right VA is shown in the neutral (E) and right-turned head positions (F). The red arrows indicate the site of vascular stenosis

Fig. 3

The right vertebral artery (VA) is susceptible to compression by the C2 transverse processes during head and neck rotation. A, B, C, D Cross-sectional digital subtraction angiography (DSA) images, with yellow arrows indicating the normal VA lumen and green arrows pointing to the narrowed segment of the vessel. E, F Three-dimensional DSA-magnetic resonance fusion image, where green arrows indicate the narrowed segment of the VA lumen

Fig. 4

Follow-up computed tomography angiography reveals no stenosis at the compression site of the right vertebral artery (A Anterior view; B Lateral view)