Ruptured Vertebral Artery Dissecting Aneurysms Involving A Dominant Posterior Inferior Cerebellar Artery Origin: A Preferred Indication For Bypass Surgery In Clinical Practice

Background: In clinical practice, the optimal treatment approach for ruptured vertebral artery dissecting aneurysm (VADA) involving a posterior inferior cerebellar artery (PICA) remains unclear. Here, we report two cases of ruptured VADA involving a dominant PICA that were successfully treated with surgical occlusion with occipital artery (OA) to PICA bypass, while avoiding postoperative ischemia.Case description: The first patient was a 47-year-old woman who presented with a Hunt-Hess grade III, diffuse subarachnoid hemorrhage (SAH) due to a ruptured right VADA involving a PICA. The PICA was dominant, supplying a wide vascular territory in the right cerebellum (the "PICA-anterior inferior cerebellar artery" variant). The second patient was a 56-year-old man who presented with a Hunt-Hess grade II, localized SAH due to a ruptured right VADA involving a PICA. The PICA was also dominant, supplying a wide vascular territory in the bilateral cerebellum (the "bihemispheric PICA" variant). Both patients were treated with OA-PICA bypass, which was followed by surgical trapping of the VADA in the first patient and proximal clipping in the second patient on the day of the SAH onset. The postoperative course was uneventful, and magnetic resonance imaging showed no apparent ischemic change in the brainstem and cerebellum in either patient.Conclusions: For ruptured VADA involving a PICA, dominance of the involved PICA may be a practically preferred indication for bypass surgery because of the severity of ischemia when a dominant PICA is sacrificed and because the vascular anatomy of a dominant PICA makes anastomosis feasible.