Operative nuances of side-to-side in situ posterior inferior cerebellar artery-posterior inferior cerebellar artery bypass procedure

BACKGROUND: An intracranial posterior circulation revascularization procedure in the form of a side-to-side in situ posterior inferior cerebellar artery (PICA)-PICA bypass operation was introduced in 1991. This elegant and apparently low-risk operation is performed infrequently. Thus, the operative nuances used in this procedure have not been well reported, limiting the scope of treatment modalities of vertebral artery-PICA aneurysms and vertebral dissections. OBJECTIVE: To repair an incidental right-sided PICA aneurysm noted in a 51-year-old woman in magnetic resonance imaging and subsequent angiography. METHODS: The patient underwent side-to-side in situ PICA-PICA bypass surgery. RESULTS: Immediate indocyanine green angiography suggested that the PICA distal to the aneurysms was filling in a retrograde fashion through the bypass. On the following day, the patient was taken for coil embolization of the aneurysm. However, angiography images revealed that the aneurysm was spontaneously thrombosed, the proximal PICA was patent, and the PICA distal to the aneurysms was filling in a retrograde fashion, as suspected in intraoperative indocyanine green angiography. No further treatments were done. The patient recovered fully. CONCLUSION: We describe in detail the preoperative evaluation, decision process, and operative techniques for a side-to-side in situ PICA-PICA bypass operation, which is a relatively safe and elegant posterior circulation bypass procedure.