Bow Hunter Syndrome Involving Rare PICA Variant (P3-5.032)

Objective: NA Background: Rotational vertebrobasilar insufficiency, also known as bow hunter's syndrome (BHS), is a rare cause of dynamic vertebral artery stenosis or occlusion during rotation of the head resulting in posterior circulation ischemia. It is potentially a reversible condition which can remain undetected and cause multiple ischemic strokes in the posterior fossa leading to significant disabilities. A 78-year-old male presented with a two-year history of transient episodes of dysarthria, vertigo, and gait disturbance lasting several minutes. These symptoms occurred after exercise or upon turning his head to the left. Dynamic transcranial doppler (TCD) revealed a significant decline in PCA flow velocities with leftward head turn followed by a hyperemic response after moving his head to a neutral position. Dynamic cerebral angiogram showed the presence of a congenitally anomalous origin of the right posterior inferior cerebellar artery (PICA) which originated at the level of C1 transverse foramen and extended under the C1 lamina. Upon neck rotation, there was near occlusion of the vertebral artery at the PICA origin. Hemilaminectomy of C1 was performed with near resolution of the patient's symptoms. A follow up TCD confirmed improvement in blood flow parameters post-operatively. Design/Methods: NA Results: NA Conclusions: This case report describes a rare presentation of BHS involving an anomalous cervical origin of right PICA. The patient underwent multiple diagnostic studies including MRIs, inner ear physiology tests, and EEGs without any formal diagnosis. The TCD provided an effective and noninvasive diagnostic modality for position related transient neurological symptoms. Frequent use of such test can help diagnose patients with BHS and improve their quality of life. Disclosure: Miss Trujillo has nothing to disclose. Miss Otero-Bell has nothing to disclose. Dr. Girotra has nothing to disclose.