Microsurgical anatomy of the extracranial—extradural origin of the posterior inferior cerebellar artery

Abstract

Five to 20% of PICAs have an extradural origin. In the case described, both PICAs arose extradurally from the third segment of the vertebral artery (VA). Both origins were less than 1 cm proximal to the site at which the VA penetrated the dura, and neither PICA gave rise to extradural branches. Extradurally, the PICAs coursed parallel to the VA and the C-1 nerve and the three structures penetrated the dura together. Intradurally, the PICAs remained lateral and posterior to the brainstem, whereas, in the common PICA configuration, the first segment of the PICA courses anterior to the medulla. Neither PICA sent branches to the anterior brainstem, which is commonly found in PICAs with an intradural origin. There were no soft-tissue or bone anomalies.

Anatomical Features and Clinical Significance of Radiculomuscular Artery Variants Involving the Suboccipital Segment of Vertebral Artery

“…We cast doubt on some reported intradural courses of V3 within the spinal canal based merely on DSA [4,6], lacking information from either intraoperative findings or anatomical dissection. Moreover, two aberrant V3s demonstrated by DSA in this series were both found to give rise to a C1 extradural origin of the PICA [2,4]. One of them was also found to give rise to a muscular branch that usually arises extradurally immediately before the dural penetration of VA [4].…”

“…1 Occipitalized atlas, 2 Transverse process of atlas, 3 Axis, 4 Spinous process of the axis, 5 Internal carotid artery, 6 Internal jugular vein terminology but for the clinical significance of the radiculomuscular artery and its radiculomedullary branch, which is often encountered during several suboccipital approaches (e.g. lateral, far lateral, suboccipital midline or upper cervical approach) [2,4]. More attention should be paid to the radiculomuscular artery from the viewpoint of surgery, to avoid complications caused by inadvertent injury to these important variants.…”

“…The course of the aberrant V3 comprised both the hyperplastic radiculomuscular artery and its radiculomedullary branch in all 6 cases. An extradural origin of PICA [2,4] was found in two of the aberrant V3s ( Fig. 4c and d), one of them also gave rise to a muscular branch ( Fig.…”

“…The microsurgical anatomy of the suboccipital segment (V3) of the vertebral artery (VA) has been previously studied [1][2][3] because of its clinical significance. The V3 is further subdivided into two parts: a horizontal (V3 h) and a vertical (V3 v) segment ( [1]; Fig.…”

“…lateral, far lateral, suboccipital midline and upper cervical) the radiculomuscular artery and its branches can be dissected [2,4] and iatrogenic injury to an important variant related to this artery or its branches poses a greater risk to PICA or even to the VA ( [1]; Fig. 1); therefore, in this study we focused on the aforementioned variations in the distal VA related to radiculomuscular artery from the viewpoint of microsurgical anatomy.…”