Sternalis Muscle: A Case Report and Literature Review

Abstract

Introduction and Objective: The sternal muscle is a rare anatomical variation found in the anterior chest wall. This study's objective was to make a narrative review of the anatomical and epidemiological aspects of the sternal muscle, as well as to present its finding in one of this group’s dissections. Materials and Methods: This study consisted of a literature review using Pubmed and LILACS platforms. Articles were analyzed regarding incidence, laterality, action, innervation, and vascularization of the sternal muscle. We also present a case report based on a cadaveric dissection of the Hospital das Clínicas, Faculty of Medicine, University of São Paulo (HCFMUSP). Results: Our review included 22 articles. The anatomical variation incidence ranged from 1.96% to 5.55%, with a higher predominance of a bilateral presentation. The action of the sternal muscle is predominantly accessory and there are divergences in the literature regarding its innervation and vascularization. Our case reports the finding of a unilateral sternal muscle in the left paramedian line inserted in both sternocleidomastoid muscles, in a female patient. Conclusion: The sternal muscle has a small incidence in the population and it is usually bilateral. The anatomical knowledge of this muscle is important to prevent it from being confused with other structures commonly found in the chest and cervical region. Significance/Implication: The importance of sternal muscle importance cannot be overlooked due to possible misinterpretations in imaging and its possible influence on mastectomies. Wider case series are necessary for a better definition of its irrigation and innervation.