Dynamic vertebral artery occlusion aka bow hunter syndrome causing posterior fossa stroke in a young adult: a case report

Bow Hunter syndrome (BHS) is a rare, but important cause of posterior circulation stroke. It is also known as Rotational vertebral artery syndrome and is caused by transient dynamic vertebro-basilar insufficiency on movement of the neck in the presence of certain soft tissue or bone anomalies in the cranio-vertebral region. We present a case of Bow hunter syndrome in an 18-year-old adult male who presented with vomiting, occipital headache and loss of balance, with findings of posterior circulation stroke on imaging. Medical causes of young stroke, including vasculitis and clotting disorders were ruled out, following which a diagnostic conventional angiography and CT angiography was performed. The cause of vascular compromise in our case was the presence of vertebral anomalies, in particular, the presence of a partial ponticulus posticus with formation of an incomplete arcuate foramen. He was treated with cervical spine immobilisation and C1–C2 fixation. In addition, our patient had a single posterior inferior cerebellar artery (PICA) on the side of the dynamic insufficiency, which lead to bilateral cerebellar infarcts. Our case is unique because it demonstrates a combination of osseous and vascular developmental anomalies resulting in posterior circulation stroke. Though uncommon, BHS should be considered in the list of differentials in otherwise unexplained cases of posterior circulation stroke. Conventional angiography with dynamic manoeuvres is the modality of choice for documenting the rotational vertebral artery occlusion.