Anatomical observation of the dorsal scapular nerve- A series of cadaver study.

Purpose: The impingement of the dorsal scapular nerve (DSN) often leads to shoulder weakness and scapular pain radiating to the upper limb. This nerve originates from a branch of the root of C5 in the brachial plexus and typically pierces the middle scalene muscle to innervate the levator scapulae, rhomboid minor, and rhomboid major muscles. Due to its anatomical location, the DSN is difficult to dissect and thus, is not often shown to medical students in lab. The purpose of this study is to show and educate medical students on the variable anatomy of the DSN. Materials and Methods: Studies were conducted on 3 embalmed adult Caucasian cadavers in which the origin, anatomical route, and muscular innervations of the DSN were dissected and documented. Results: It was found that the DSN originated from C5 spinal nerve root in two cadavers whereas in one cadaver, the DSN branches from C4. The route of the DSN varies either by passing anteriorly to the scalene muscles or piercing through the middle scalene muscle in order to travel posteroinferiorly to its targeted muscles. The DSN innervated only the rhomboid muscles in one cadaver and in the other two cadavers, this nerve innervated the rhomboid muscles as well as the levator scapulae muscle. Conclusions: The variations of the DSN spinal contribution, route, and muscle innervations are identified in this study. Such variations will help clinicians become better aware of its anatomy in order to make the appropriate diagnosis and treatment plan to patients with pain related to DSN impingement.