Anatomical Basis of the Occipital Artery-Posterior Inferior Cerebellar Artery Bypass (OA-PICA Bypass)

Revascularization allows the restoration of blood flow to a brain territory deprived of it, and a solid knowledge of cerebral vascular anatomy forms the foundation for mastering this practice. The aim of this study was to describe the main anatomical elements involved in the occipital artery-posterior inferior cerebellar artery technique and to briefly present the anastomosis procedure in cadaveric preparations. Four heads with cerebellums fixed in 5 % formalin were used. The dissections were carried out with left-hand forceps, scissors, 9-0 sutures, a high-resolution photographic camera, microdissection instruments, latex, and resin. The dissection of the occipital artery and the posterior inferior cerebellar artery (PICA) corresponded to classical anatomical and neurosurgical descriptions. Each segment of the PICA and its relationships with posterior fossa neural structures were exposed. The bypass performed in cadaveric preparations highlighted the importance of acquiring this skill through laboratory training before clinical application. The dissections allowed visualization of the vertebral artery with its segments V1–V4; the PICA with its five segments, anterior medullary, lateral medullary, amygdalo-medullary, telo-velo-tonsillar, and cortical; and the occipital artery with its three segments, oblique ascending, transverse, and vertical ascending. Both in the initial approach and during intraoperative microsurgical dissection, preserving the integrity of these vessels requires significant technical expertise, which can only be achieved through repeated laboratory practice. In summary, vascular neuroanatomy revealed the detailed segmentation of the occipital and PICA arteries, confirming their anatomical relationships with neural structures such as the pons, medulla, fourth ventricle, and cerebellum. The bypass practice in cadaveric specimens demonstrated that it is possible to successfully develop the technique under the microscope, reinforcing the necessity of laboratory training before performing it in the operating room with patients.