A Unique Presentation of an Upper Subscapular Nerve Variation Accompanied by an Accessory Subscapular Artery.

The presence of an upper subscapular nerve branching from the posterior division of the superior trunk, and it being accompanied by an accessory subscapular artery, is of both clinical and surgical significance. During routine dissection of the root of the neck in a 75-year-old male cadaver, an unusual branch from the third part of the right subclavian artery was observed lateral to the dorsal scapular artery. Continued dissection revealed that this artery traveled between the anterior divisions of the superior and middle trunks of the brachial plexus before traveling alongside a nerve from the posterior division of the superior trunk of the brachial plexus. This artery and nerve descended on the anterior aspect of the subscapularis muscle before piercing into its muscle belly. We believe this to be a previously unreported unique variation of the upper subscapular nerve that is accompanied by an accessory subscapular artery on its course to the subscapularis muscle. Knowledge of anatomical variations like this may lead to decreased complications in nerve blocks and surgical procedures related to the shoulder.