ABSTRACT NUMBER: ESOC2026A900 RECURRENT VERTEBROBASILAR STROKE DUE TO INVERSE BOW-HUNTER SYNDROME: A CASE REPORT

Abstract Background and aims Bow-Hunter syndrome is a rare cause of ischemic stroke due to compression of the vertebral artery (VA) during head rotation. We describe an unusual “Inverse Bow Hunter” variant. Methods A 50-year-old male with recurrent embolic posterior circulation strokes presented to our tertiary stroke center. Prior CT revealed proliferative osseous changes of the left superior articular process of C6, causing narrowing of the ipsilateral transverse foramen and focal stenosis of the left VA (V2 segment). We performed dynamic digital subtraction angiography (DSA) and duplex sonography of positional hemodynamics. Results DSA in a neutral head position confirmed stenosis of the left V2 segment with absent antegrade flow and collateral filling of distal VA segments via the ascending cervical artery. Dynamic imaging revealed that maximal leftward head rotation resulted in markedly reduced VA flow, whereas maximal rightward rotation successfully restored antegrade flow. Duplex sonography corroborated these findings, demonstrating reduced flow in the neutral position, normalization during leftward rotation, and a stenotic flow pattern during rightward rotation. Subsequent MRI identified new silent embolic cerebellar infarcts. Following a multidisciplinary discussion of therapeutic options, the patient was maintained on antiplatelet therapy, and surgical resection of the compressive osseous structure was scheduled. Conclusions This case illustrates a rare “Inverse Bow Hunter” variant with flow arrest in neutral head position and relief during head rotation, where hemodynamic changes may lead to thromboembolic strokes. Dynamic imaging in rotated head positions may hence be helpful in the workup of suspected vertebral artery stenosis. Conflict of interest Martin Arndt: nothing to disclose; Pawel Krukowski: nothing to disclose. Timo Siepmann: nothing to disclose. Hagen B. Huttner: nothing to disclose. Ilker Eyüpoglu: nothing to disclose. Daniel P.O. Kaiser: nothing to disclose.