Pearls & Oy-sters: Bow hunter syndrome: A rare cause of posterior circulation stroke

A 24-year-old man with no relevant medical history presented to our institution with a week of intermittent dizziness exacerbated by turning his head to the left. He acutely developed diplopia and disorientation on the day of presentation to the emergency room. He reported similar complaints a month prior. There was no history of fevers, rashes, headache, or neck trauma. There was no family history of similar complaints, vascular or connective tissue diseases, stroke-like episodes, seizures, or early-onset dementia. Examination demonstrated mild impairment of cognition and a right hemiparesis. Initial head CT revealed congenital atlas nonunion (C1) with fusion of the second and third vertebral bodies (C2–C3). Brain MRI revealed diffusion restriction in the left thalamus and bilateral dorsal midbrain indicative of multiple acute infarctions. Chronic infarctions were also present in the right cerebellum, which indicated prior episodes of ischemia. A series of dynamic X-rays showed malalignment of the lateral masses of the atlas with C2, but there was no evidence of instability. CT angiography (CTA) revealed the presence of a pseudoaneurysm of the right VA at its exit from the C2 transverse foramen. This was suspected to be the source of the posterior circulation emboli. Left VA was unremarkable. There was no evidence of VA dissection on CTA (figure). Magnetic resonance angiography (MRA) with fat-suppressed images of the neck was not performed. The rest of the workup including complete blood count, serum chemistry and lipids profile, glycosylated hemoglobin levels, liver function tests, hypercoagulability studies, D-dimer levels, transthoracic echocardiography, and short-term Holter monitoring were unremarkable. A transesophageal echocardiogram was not performed because of concerns for further neck manipulation.