ONS Advance Access: Variations of Occipital Artery-Posterior Inferior Cerebellar Artery Bypass: Anatomic Consideration

Microsurgical and endovascular techni-ques have improved surgical treatment of aneurysms involving the posterior inferior cerebellar artery (PICA).122 Distal intracranial aneurysms are quite rare, but recent reports revealed distal PICA aneurysms to be relatively frequent.20,23 The surgical treatment of these aneurysms, involving either the proximal or distal PICA, is consistently challenging because of the multiple anatomic variations of the parent vessels, their deep location in the posterior cranial base with close relation to the brainstem and lower cranial nerves (CNs), and the variation of location.3,4,9,21,24 In addition, these aneurysms may cause mass effects such as lower CN palsy, rupture at a small size, have a greater rate of rebleeding, and a high proportion of fusiform, dissecting, or wide-neck aneurysms.3,4,11,13,16,19,22,24

Despite advances in endovascular techniques, PICA aneurysms sometimes require revascularization procedures with parent vessel occlusion.23,2527 The caudal loop of PICA has been most frequently utilized for either the occipital artery (OA)-PICA bypass or PICA–PICA side-to-side anastomosis to achieve sufficient revascularization in such cases.25,26,28

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