Importance of the course of the accessory nerve on the neck region for surgical procedures

Aim: In this study, through the evaluation of the accessory nerve with cadaver dissection in the neck region, we aimed to contribute to the scientific and technological improvements of current and newly developed surgical techniques in terms of surgical interventions. Methods: In the Application and Research Laboratory of the Anatomy Department of Dokuz Eylul University Faculty of Medicine, from May 2017 to May 2018, bilateral neck dissections were performed on eight formaldehyde fixed adult male cadavers of unknown age. After marking the reference points, the measurements were taken with a digital caliper. Data were analyzed using SPSS 21.0 program and p<0.05 was accepted as statistically significant. Results: On the lower edge of the posterior belly of the digastric muscle, the accessory nerve crossed the internal jugular vein anteriorly in 10 sides (62.5%). The accessory nerve directly penetrated the sternocleidomastoid muscle in 14 sides (87.5%), and after the separation of the branch going to the sternocleidomastoid muscle, we observed that the accessory nerve passed this muscle posteriorly in 2 sides (12.5%). On the posterior edge of the sternocleidomastoid muscle, the exit point of the greater auricular nerve was mostly identified inferior (81.25%) to the exit point of the accessory nerve, and the distance between these two points was measured 14.36±6.56 mm. At the posterior edge of the sternocleidomastoid muscle, the distance between the exit point of the accessory nerve and the mastoid process was 62.95±12.37 mm. The length of the accessory nerve in the posterior neck region was 52.3±9.88 mm; and in two cadavers, the accessory nerve was tortios in this region. Conclusion: To reduce the risk of the accessory nerve damage and shoulder syndrome during surgical interventions, it is important to know the position, the course and the distances of some reference anatomical structures on the lower edge of the posterior belly of the digastric muscle, the posterior edge of the sternocleidomastoid muscle and the anterior edge of the trapezius muscle.