Bowhunter's syndrome diagnosed with provocative digital subtraction cerebral angiography

Abstract

Bowhunter's syndrome, also known as rotational occlusion of the vertebral artery, involves posterior circulation ischemia resulting from dynamic compromise of the dominant vertebral artery. This case highlights the importance of provocative digital subtraction angiography in making the diagnosis. A 41-year-old man presented for outpatient neurological evaluation for "lightheadedness" of several years' duration provoked by leftward head rotation. The only abnormality identified on initial magnetic resonance angiography was atresia of the nondominant left vertebral artery. Conventional digital subtraction angiography (DSA) followed by provocative DSA revealed development of a dynamic stenosis of the right vertebral artery involving the extraforaminal segment just superior to the C1 vertebra. Noncontrast computed tomography of the cervical spine confirmed ossification of the posterior right atlanto-occipital membrane leading to a near complete bony arcuate foramen. Following neurosurgical decompression, the patient demonstrated complete resolution of all neurologic symptoms. Bowhunter's syndrome is a unique clinical entity that must be considered in the evaluation of patients with symptoms of posterior circulation ischemia. Provocative DSA remains the preferred modality for definitive diagnosis.

Figure 1

Digital subtraction angiographic image of the posterior circulation demonstrates patency of the right vertebral artery without evidence of significant focal stenosis.

Figure 2

Dynamic digital subtraction angiographic image obtained following leftward rotation of the patient's head reveals development of a severe stenosis of the right vertebral artery involving the extraforaminal segment just superior to the C1 vertebral body.

Figure 3

CT images through the cervical spine obtained in the bone window in the (a) axial and (b) sagittal planes demonstrate ossification of the posterior right atlanto-occipital membrane.