Dual Origin of Extradural Posterior Inferior Cerebellar Artery From Vertebral and Occipital Arteries

Small anastomotic channels exist between the occipital artery (OA) and muscular branches of the vertebral artery; however, no direct connection has been reported between an extradural origin of the posterior inferior cerebellar artery (PICA) and the OA.To describe a rare anatomic connection between the extradural PICA and the OA.A far lateral exposure was completed on a cadaveric head prepared for surgical simulation. The course and branches of the OA were followed, and the relations to their immediate anatomic structures were studied.The origin of the PICA was found at the second segment of the vertebral artery, between the C1 and C2 transverse foramina. There was a large anastomotic connection between the superficial descending branch of the occipital artery and the PICA 12 mm proximal to the dural entrance of the artery.Awareness of the angioarchitecture of the suboccipital region and the existence of patent vertebrocarotid anastomotic connections is important to avoid complications during surgical or endovascular interventions. When present, a pre-existing OA-PICA anastomosis can be exploited to facilitate treatment in certain vascular pathologies (eg, vertebral artery aneurysms). Awareness of the existence of both an extradural origin of the PICA and a direct connection of this vessel with the OA is of great relevance to the muscular stage of surgical approaches to the posterior craniovertebral junction.