Posterior inferior cerebellar artery reimplantation: buffer lengths, perforator anatomy, and technical limitations.

OBJECTIVE Reimplantation of the posterior inferior cerebellar artery (PICA) to the vertebral artery (VA) is a safe and effective bypass option after deliberate PICA sacrifice during the treatment of nonsaccular and dissecting aneurysms at this location. However, the anatomy and limitations of this technique have not been studied. The goal of this study was to define the surgical anatomy and buffer lengths specific to the proximal segment of the PICA related to 2 variations of PICA reimplantation: 1) reimplantation "along-VA" (simulating a dissecting VA aneurysm), and 2) reimplantation "across-VA" (simulating a nonclippable, proximal PICA aneurysm). METHODS Ten cadaver heads (20 sides) were prepared for surgical simulation. Twenty far-lateral approaches were performed. The PICA was mobilized and reimplanted onto the VA according to 2 different paradigms: 1) transposition along the axis of the VA (along-VA) to simulate a dissecting VA, and 2) transposition perpendicular to the axis of the VA (across-VA) to simulate a nonclippable, proximal PICA aneurysm. The buffer lengths provided by mobilization of the artery in each paradigm were measured and the anatomy of perforator branching on the proximal PICAs was analyzed. RESULTS The PICA was reimplanted in all surgical simulations. The most common perforating artery on the P and P segments was the short circumflex type. No direct perforator was found on the P segment. The mean buffer length with reimplantation along the VA axis was 13.43 ± 4.61 mm, and it was 6.97 ± 4.04 mm with reimplantation across the VA. The PICA was less maneuverable when it was reimplanted across the VA, due to perforator branches of the PICA (P segment). CONCLUSIONS The buffer lengths measured in this study describe the limitations of PICA reimplantation as a revascularization procedure for nonsaccular aneurysms in this location. PICA reimplantation is a revascularization option for dissecting VA aneurysms incorporating the PICA origin that are < 13 mm in length, and for nonsaccular proximal PICA aneurysms that are < 6 mm in diameter. The final decision to reimplant the PICA depends on careful inspection of perforator anatomy that is not visible preoperatively on angiography, as well as an assessment of technical difficulty intraoperatively.