Introduction: The existing classification of the cerebellar arteries is based on landmarks that might not be commonly encountered during routine surgical procedures (1). The anatomic relationship between neurovascular structures around the brainstem can provide a useful orientation tool while navigating this complex region. This cadaveric study aims to propose a novel nomenclature for the peritruncal cerebellar arteries, viz. Superior Cerebellar Artery(SCA), Anteroinferior Cerebellar Artery(AICA) and Posteroinferior Cerebellar Artery(PICA), using the cranial nerves as anatomic landmarks.

Methods: The course of the peritruncal cerebellar arteries was studied anteriorly via the rostrocaudal expanded endoscopic endonasal approach (EEA) and laterally via the following approaches: subtemporal for SCA, anterior transpetrosal for AICA and far-lateral for PICA, in 10 specimens. The length of the proposed segments, the relationship and distance between the arteries and their corresponding cranial nerves were recorded

Results: Starting form its origin and based on its closest vertical point with CN III-V, the SCA was divided into 3 segments: occulomotor, trochlear and trigeminal. The mean length of these segments was found to be 8.0mm, 5.2mm and 8.0mm, respectively. The mean caudal distance between SCA and the CNV was 6.0mm. In all the specimens, the SCA was in contact with CNIII and CNIV. The AICA was divided in 2 segments: abducens and facio-vestibular. The mean length of these segments was 6.9mm and 15.9mm, respectively. The PICA was divided in 2 segments: hypoglossal and accessory. The mean lengths of these segments were 3.3 mm and 13.1mm. The mean distance between the PICA and CN XII was 1.35 mm and it was in contact with the CN XI in all specimens.

Conclusions: The proposed segmentation of the peritruncal cerebellar arteries utilized structures routinely exposed during microsurgical and EEA. This classification could be a practical tool for intraoperative neurovascular orientation and navigation during vascular and skull base procedures.

Patient Care: Using this segmentation will help provide better understanding of peritruncal neurovascular structures allowing surgeons to be more cognizant of these critial relationships while performing routine skull base approaches and helping them prevent inadvertant introperative damage.

Learning Objectives: 1. Understand the anatomy and the course of the Superior Cerebellar Artery (SCA), Anteroinferior Cerebellar Artery (AICA) and Posteroinferior Cerebellar Artery (PICA) 2. Understand the relationship between cerebellar arteries and the cranial nerves in their vicinity 3. Be able to apply the proposed classification intra-operatively using the described surgical landmarks.

References: 1 A. Rodriguez-Hernandez. Segmental anatomy of cerebellar arteries: a proposed nomenclature. 2011. J Neurosurg. 115: 387-397.