Vertebral Artery-Posterior Inferior Cerebellar Artery (PICA) Aneurysm Treated With the PICA-to-PICA Bypass: A Case Report.

Treating vertebral artery-posterior inferior cerebellar artery (VA-PICA) aneurysms poses challenges because of their complex anatomy. Although endovascular treatment is commonly preferred, direct surgery offers better recovery prospects than endovascular surgery aided by bypass techniques. We present a VA-PICA aneurysm case treated with VA internal trapping, using a PICA-to-PICA bypass without direct clipping. A 64-year-old man presented with complaints of severe headache and was diagnosed with a right VA-PICA wide neck aneurysm. The PICA originated from the neck of the aneurysm. We consulted an endovascular surgeon and opted for direct clipping via the transcondylar fossa approach. During surgery, we secured and followed the right VA, identified the PICA origin, and observed the proximal neck of the aneurysm. However, securing the distal VA was challenging because the dissector was inaccessible. Instead of direct clipping, a PICA-to-PICA bypass was selected following internal trapping. After anastomosis, the proximal PICA was occluded, whereas the small perforating artery was preserved. The next day, internal trapping of the right VA was performed. The patient's postoperative course was uneventful, except for mild dysphagia. Head magnetic resonance imaging revealed a small infarction on the right medulla. Three-dimensional computed tomography angiography revealed perfect PICA-to-PICA bypass patency. The patient was subsequently transferred to a rehabilitation hospital. The patient had no neurological symptoms at the six-month follow-up (Modified Rankin Score = 0). The preoperative feasibility of direct clipping of complex PICA aneurysms while preserving PICA is unpredictable. Various bypass methods, including the PICA-to-PICA bypass, are potential treatment options for complicated VA-PICA aneurysms.