Introduction: Occipital artery (OA)-posterior inferior cerebellar artery (PICA) bypass has been used for posterior fossa revascularization. OA-PICA bypass is technically challenging because of its deep and narrow surgical corridor. When the caudal loop of PICA is unavailable as an optimal recipient, OA-PICA bypass could be more challenging.
Methods: The authors simulated OA-PICA bypass using 5 adult cadaveric specimens. The complex microsurgical anatomy of the lateral foramen magnum was examined in stepwise dissections, and feasibility of OA-PICA bypass to various segment of PICA was assessed through far-lateral approach. In addition, 7 patients underwent OA-PICA bypass surgery for hemodynamic ischemia or ruptured dissecting aneurysm (DA) of the posterior fossa. In these cases, clinical significance of the caudal loop as an optimal recipient, and technical difficulty of bypass procedure related to anatomical variation of the caudal loop were evaluated.
Results: The caudal loop as an optimal recipient was available in 4 out of 7 cases, where OA-PICA bypass was less demanding even when resection of the condylar fossa was incomplete. In the other 3 cases, the caudal loop was missing and the other segment was selected as a recipient. OA-PICA bypass was also completed through the surgical corridor provided by the far-lateral approach, although one bypass of the most difficult case was occluded on the next day.
Conclusions: Technical feasibility of OA-PICA bypass depends on presence of the caudal loop of PICA as an optimal recipient. Far-lateral approach is recommended particularly when the bypass is demanding because of anatomical variation of PICA.
Patient Care: Our research will contribute to raise the success rate of challenging OA-PICA bypass.
Learning Objectives: By the conclusion of this session, participants should be able to discuss anatomical variation of the caudal loop of PICA and optimal craniotomy for OA-PICA bypass