Abstract
The carotid sheath (CS) is a fibrous tunnel in the neck, one in each side, that serves to transport the internal carotid artery (ICA), common carotid artery (CCA), internal jugular vein (IJV), and vagus nerve (CN X) as they exit the skull base at the jugular foramen, transverse the neck and enter the thorax. Awareness of CS anatomy is very pertinent in the clinical context. Several pathologies associated with the sheath, include neural sheath tumours, paragangliomas, metastatic lymph nodes, phlebitis, and thromboembolism. However, complex aspects of CS anatomy are still not well-understood. These gaps include its origin, fascial contributions, spatial positioning of the sheath’s contents, subdivisions within the sheath, and relationships with surrounding structures. Some authors have even argued against the existence of a discrete sheath structure in the neck. Therefore, the overall aim of this study was to investigate the fine architecture of the upper CS and its structural relationship with the posterior group of the cranial nerves (CNs IX-XII). The hypotheses of this work were (1) the upper CS is an aponeurosis tube that made up of discontinuous walls from multiple muscular origins; and (2) the 3D fine architecture of the upper CS is closely correlated to the course of the posterior group of the cranial nerves entering and leaving the sheath. In this study, the upper CS refers to part of the CS above the level of the hyoid bone, or in the suprahyoid neck.