Dissecting posterior inferior cerebellar artery (PICA) aneurysms typically have nonsaccular morphology, involve an entire segment of artery, and are unclippable. Exclusion of these ruptured aneurysms can be accomplished endovascularly or microsurgically by sacrificing the parent artery, but revascularization of the PICA territory can only be accomplished microsurgically. In situ bypass with a side-to-side anastomosis between the caudal loops of PICA bilaterally is an attractive option for these aneurysms. This video demonstrates trapping and side-to-side anastomosis of a ruptured proximal PICA aneurysm. This 28-yr-old woman presented with sudden headache and nausea, and angiography demonstrated a fusiform dissecting aneurysm at the left PICA origin measuring approximately 6 mm in diameter. A left far lateral craniotomy exposed the left PICA aneurysm, and it was not amenable for direct clipping or end-to-end reconstruction. Key technical points of the PICA–PICA in situ bypass include the following: extensive arachnoidal dissection to bring the p3 segments together without tension; arteriotomies 3 times the diameter of the arteries; continuous intraluminal suturing of the first suture line; continuous extraluminal suturing of the second suture line; and preservation of medullary perforators. Indocyanine green videoangiography confirmed patency of the bypass; the aneurysm was trapped and excised. The patient tolerated the operation well and made an excellent recovery (modified Rankin Scale score 0 at 6 mo). The PICA–PICA in situ bypass is an effective option when end-to-end reanastomosis is not possible, and it has a lower risk profile than PICA reimplantation onto the vertebral artery.
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