Measurements and new definitions related to the accessory nerve in neck dissections

Introduction and Purpose: To prevent Nervus Accessorius (ACC) damage in patients who performed neck dissection, we aimed to define new reference points for easier exploration and protection of the nerve through neck morphological measurements and the relationship of the nerve with important anatomical structures in the neck. Materials and Methods: Our study was planned prospectively at Karadeniz Technical University Faculty of Medicine Ear Nose and Throat Clinic between October 2021 and September 2023. Some preoperative and perioperative measurements were made in millimeters (mm) for the patients. Results: The mean age of 59.2±17.07 (18-90) of 80 patients, 54 were men and 26 were women. According to the Spearman Correlation Test, there was a positive correlation between the distance between the Great auricular nervus (GAN)- (ACC) and the Sternocleidomastoid muscle (SCM) thickness (ρ=0.242, p = 0.03). There was a positive correlation between the distance between GAN and ACC and the length of the ACC from the point where it exits the posterior border of the Scm and enters the trapezius muscle (ρ=0.307, p = 0.006). There was a positive correlation between the distance between GAN-ACC and the distance between the mastoid apex and clavicle midline measured preoperatively (ρ=0.235, p = 0.036). There was a positive correlation between neck circumference, scm length, scm circumference, and scm thickness (ρ=0.248, p = 0.026), (ρ=0.354, p = 0.001), (ρ=0.346, p = 0.002, respectively). Conclusion: It is very important to protect N.Accessorius during head and neck surgeries. We recommend that surgeons take into account the morphological characteristics of the patients and the new definitions and clues we stated in our study when finding and protecting the nerve. Key Words: Neck Dissection, Accessory Nerve, Great Auricular Nerve