Jacobs Journal of Anatomy and Physiology

Petroclival Canal: A Rare Passage of the Abducens Nerve at the Petroclival Region-Anatomic Variation

*Selim Kayaci
Department Of Neurosurgery, Recep Tayyip Erdogan University, Kirikkale, Turkey
*Fernando Anschau
Department Of Medicine, Recep Tayyip Erdogan University, Porto Alegre , Brazil

*Corresponding Author:
Selim Kayaci
Department Of Neurosurgery, Recep Tayyip Erdogan University, Kirikkale, Turkey
Email:jeff.carroll@ars.usda.gov Fernando Anschau
Department Of Medicine, Recep Tayyip Erdogan University, Porto Alegre , Brazil
Email:anschau@terra.com.br

Published on: 2018-12-20

Abstract

Petroclival canal (PCC), which occurs as a result of petrosfenoidal ligament (PSL) calsification is a different passage for the abducens nerve path. During performing the anatomic dissection of petroclival region of a the cadaveric specimen, we incidentally noted existence of a bony canal in which abducens nerve was passing through petro-occipital fissure (POF), petroclival canal. This variation was also confirmed by thin sections of computed tomography images. PSL was found as a thin fibrous band between the petrous apex and posterior clinoid process at an interdural space, however the sixth cranial nerve were passing through bony canals in the petro-occipital fissures to the superior posterior side of the lacerum segment of the internal carotid artery on both sides. Passage of the abducens nerve through a bony canal is presumed to be clinically important in terms of fractures reaching up to the petroclival region and there is a risk of nerve injury during both anterior transpetrosal or endoscopic approaches through the petroclival region.

Keywords

Abducens Nerve, Ossification, Petro-Clival Canal, Petro sphenoidal Ligament

Introduction

Abducens nerve has 3 trapping points in the petroclival region. These are: the dural entry hole, transit area between PSL and petrous apex, and the area where internal carotid artery has anastomosis with sympathetic plexus on the lateral wall. In case of a trauma, the trapping of the nerve on these points due to fierce movement of the head (flexion, extension) can result in nerve palsy. The course of the abducens nerve through a bony canal, as in our case may result in nerve damage in case of a fracture reaching up to the petroclival region as opposed to a possible damage seen in the most frequently encountered course of the nerve. In the literature, there is no report of abducens nerve palsy in a patient whose PCC is identified in an isolated way, however, the presence of ossification can be identified at least in some patients with petroclival fractures with the help of thin sliced computed tomography (CT). Existence of the bony canal inside the petrooccipital fissure may cause consideration of the idea of possible nerve damage in the diastatic fractures of skull base characterized by the diastasis of sutures [2]. Many patients with bilateral VIth nerve palsies after a head injury have an underlying fracture of the clivus. Furthermore, the fact that the dural sheath of the nerve has an arachnoid membranous extension may also bring up the idea that the dural sheath injury, in such a variation, may be an important factor in cerebrospinal fluid leak.