The Relation of the Extracranial Spinal Accessory Nerve to the Sternocleidomastoid Muscle and the Internal Jugular Vein

Abstract

The spinal accessory nerve (SAN) exhibits variant anatomy in its relation to the internal jugular vein (IJV) as well as the sternocleidomastoid muscle (SCM). These variations are important in locating the nerve during surgical neck procedures to avoid its inadvertent injury. These variations, however, are not conserved among different populations and data from the Kenyan setting are partly elucidated. This study, therefore, aims to determine the variant anatomical relationship of the SAN to the SCM and IJV in a select Kenyan population. Forty cadaveric necks were studied bilaterally during routine dissection and the data collected were analyzed using SPSS version 21. Means and modes were calculated for the point of entry of the SAN into the posterior triangle of the neck as well as for its relation to the SCM. Side variations for both of these were analyzed using Student's t-test. Data relating the SAN to the IJV were represented in percentages and side variations were analyzed using the chi-square test. The SAN point of entry into the posterior triangle of the neck was 5.38 cm (3.501–8.008 cm) on the left side and 5.637 cm (3.504–9.173 cm) on the right side ( p = 0.785) from the mastoid process. The nerve perforated the SCM in four cases (10%) on the left side and in eight cases (20%) on the right ( p = 0.253). The SAN lay predominantly medial to the IJV on both sides of the neck, 87.5% on the left side of the neck versus 82.5% on the right ( p = 0.831). In conclusion, the variant relation of the SAN to the IJV and SCM as observed in this setting is an important consideration during radical neck procedures and node biopsies.

The spinal accessory nerve and its entry point into the posterior triangle of the neck

“…There have been many attempts within the literature to describe the course of the spinal accessory nerve and to define its point of entry into the posterior triangle of the neck in relation to surrounding structures [8]. This includes distance from the clavicle [8,9], the mastoid process [3,4,8,11,12,23], the angle of the mandible [23], the greater auricular nerve [21] as well as, similar to this study, the distance along the posterior border of sternocleidomastoid from its superior insertion point [1,2,13,21,22].…”

Spinal accessory nerve anatomy in the posterior cervical triangle: A systematic review with meta‐analysis

“…The flow chart of the strategy used in this search is presented in Figure 1. A total of 25 studies ( n = 1346 heminecks, n = 798 subjects) were included in the final analysis, spanning a time from 1986 to 2023 (Table 1) (Abakay et al, 2020; Amirlak et al, 2020; Amuti et al, 2019; Anehosur et al, 2021; Aramrattana et al, 2005; Caliot et al, 1989; Chen et al, 2009; Dailiana et al, 2001; Diop et al, 1987; Durazzo et al, 2009; Ellis et al, 2023; Khavanin et al, 2019; Kierner et al, 2000; Krause et al, 1991; Lu et al, 2002; Peck & Luce, 1988; Raikos et al, 2017; Salgarelli et al, 2009; Shiozaki et al, 2007; Soo et al, 1986; Symes & Ellis, 2005; Tubbs et al, 2005; Vargas et al, 2009; Vathana et al, 2007; Wirth et al, 2011). Twenty‐two studies were cadaveric ( n = 1206 heminecks), and three studies were prospective intraoperative ( n = 140 heminecks).…”

Anatomic Relationship between the Spinal Accessory Nerve and the Internal Jugular Vein in the Upper Neck during Neck Dissection: A Prospective Study

“…Then it passes to the JF where it receives some fibers from the cranial root. The SAN exits the JF with the ninth and tenth cranial nerves as well as the internal jugular vein (IJV) [2][3][4].…”

“…al conducted a study in 181 and 80 ND, where the SAN was located medial to the IJV in 104(57.4%) and 68(85%), and lateral to the IJV in 72(39.8%) and 12(15%) of the cases respectively. [6,17] Few previous studies have reported on the incidence of the SAN passing through the fenestrated IJV. Hollinshead reported identifying 3.2% during cadaver dissection, Prades et.…”

“…ISSN: 2332-4139 observed in the Nepalese population. Knowledge of these variations is important in locating the SAN and avoiding its inadvertent injury during neck procedures such as node biopsies, SAN blocks, and radical neck surgeries [17,18] to avoid the morbidity associated with SAN injury. Therefore, the primary objective of the study is to find the intraoperative relationship between the SAN and the IJV in the upper neck, at the level of superior border of PBD muscle.…”