Multiple Lateral Cervical Musculature Variation: A Case Report

Abstract

Introduction: The paired anterior, middle, and posterior scalene muscles are found in the lateral neck. The anterior scalene originates from the transverse processes (TPs) of C3-C6 and inserts on the first rib. The middle scalene originates from the TPs of C2-C7 and also inserts on the first rib. The posterior scalene originates from the TPs of C5-C7 and inserts on the second rib. The levator scapulae originates from C1-C4 and inserts on the angle of the scapula. This case report documents multiple anatomical variations of the scalenes and levator scapulae in the lateral neck. Background: While there have been case studies on other scalene variations, including the scalenus minimus, there are no documented cases matching the morphologies noted here. Case Findings: Detailed dissection revealed multiple muscle variations. The first, an accessory middle scalene muscle with two bellies. The superior belly originates at C1-C5 TPs, running in an inferomedial fashion, anterior to the middle scalene. The inferior belly runs in an inferior fashion, anterior to the middle scalene, with some fibers inserting on the middle scalene and the remainder merging with the first intercostal fibers. The second, an accessory levator scapulae muscle, with two bellies coming off the 3rd belly of levator scapulae and attaching to C5. The final variation, the posterior scalene muscle attaching to the first rib instead of the second. Conclusion: Some possible clinical implications of this variant include cervicogenic headaches, thoracic outlet syndrome, and compression of the brachial plexus.