Teaching Case

A 15-year-old female with a history of frequent episodes of neck pain and loss of consciousness. History of fall 1 month ago.

A CT spine was done, which was suggestive of the assimilation of the occipital condyles with the superior articular facets of C1 bilaterally and the fusion of C2 and C3 vertebral bodies (Figures 1a, 1b, 1c and 1d). A CT angiogram further revealed hypoplastic left vertebral artery (Figure 2). MRI of the cervical spine with flexion and extension showed no evidence of cord compression (Figures 3a, 3b and 3c). DSA of the right vertebral artery was normal (Figures 4a and 4b). Left vertebral angiogram (DSA) showed hypoplastic left vertebral artery, which terminated as posterior inferior cerebellar artery (PICA). DSA on neck rotation showed stasis in the proximal vertebral artery segment with non-opacification of the distal segment and left PICA (Figures 5a, 5b, 5c and 5d).

Bow Hunter’s syndrome is an uncommon illness that results in transitory vertebrobasilar insufficiency caused by dynamic neck motion and even a posterior circulation stroke [1–3]. Also known as rotational occlusion of the vertebral artery, blood flow may be compromised in a patient if their dominant vertebral artery undergoes dynamic compression, and may even lead to stroke. Because of collateral from either the anterior circulation or from the contralateral vertebral artery (VA), positional compression of VA is usually asymptomatic. However, when the dominant VA is compromised with insufficient collateral circulation, the patient becomes symptomatic [1,3,4].

Tatlow and Bammer initially proposed the term in 1957 to characterise a patient who experienced Wallenberg syndrome. Sorensen first used the phrase “Bow Hunter’s syndrome” in 1978 [1,3].

Large osteophytes, fascial bands of paravertebral musculature, atlantoaxial excessive mobility, tumours, and malformed vertebrae are a few possible aetiologies. Given the artery’s relative immobilisation at the foramen transversarium, the atlantoaxial junction is the most often occluded site [1,2]. However, it may occur anywhere along the vertebral artery’s course. A posterior inferior cerebellar artery (PICA) branching off of a vertebral artery (VA) has been reported to be a typical variant linked to VA hypoplasia [5].

The fifth to seventh decade of life comprises the time symptoms typically manifest, with a significant male predominance. A “two-hit” paradigm explains the mechanism. One of the vertebral arteries is severely hypoplastic or stenotic in the beginning. In the second hit, an anatomical variation or anomaly, such as a disc herniation and bony spurs, affects the contralateral vertebral artery [1,3]. It may occur from compression of a non-dominant PICA–VA, which can have even more serious consequences [5].

The diagnosis is not always ruled out by non-invasive neurovascular imaging. Provocative cerebral angiography is still the gold standard for diagnosis; this involves reproducing or exacerbating symptoms such as headaches, nausea, dysarthria, momentarily blurred vision, and transitory vertigo when there is neck rotation [1].

Options for treatment include surgical and/or conservative approaches. Conservative methods involve employing cervical collars, antiplatelet, or anticoagulant medications. The surgical method involves decompression with/without fusion of endovascular stents within the unaffected vertebral artery [1,2].

Our case puts forward a rare cause of the rare entity, as the patient was a young female who had symptoms due to compression of the hypoplastic vertebral artery, which was terminating as a posterior inferior cerebellar artery.

Written informed patient consent for publication has been obtained.