Accessory head of sternocleidomastoid-a case report

Abstract

As many important nerves emerge from the posterior border of sternocleidomastoid (SCM), it is important to know the morphological anatomy of sternocleidomastoid for surgical as well as radiological purpose. During routine dissection of head and neck for student demonstration, an accessory head of sternocleidomastoid was found arising from the superior surface of the middle third of the clavicle on the right side of the neck. Sternocleidomastoid is a key landmark as it divides the neck into anterior and lateral regions (anterior and posterior triangles respectively. Morphological variations arise due to the complexity of sequential development of any region. SCM is an important surgical landmark for clinicians. A well versed knowledge of its variations can avoid diagnostic and surgical complications.

Sternocleidomastoid Muscle in Fetuses: Classification, Morphometric Analysis, and Clinical Significance

“…As a result of the literature review, a total of 40 cases (57 SCM) were reached published in 32 case reports and 2 original studies related to SCM variations (Supplementary Table 10, Supplemental Digital Content 10, http://links.lww.com/SCS/E795). 5–7,10,14,16–44 In 40 cases, variations were detected using different methods such as dissection, surgery, magnetic resonance imaging, and ultrasonography. Distribution order of SCM types in the literature (40 subjects, 57 sides), from largest to smallest, was reported as Type 2a (35 sides)>Type 4 (9 sides)>Type 2b (4 sides)>Type 3 (3 sides)>Type 6 (2 sides)>Type 2c (1 side)=Type 2d (1 side)=Type 2e (1 side)=Type 5 (1 side) (Supplementary Table 10, Supplemental Digital Content 10, Supplemental Digital Content 10, http://links.lww.com/SCS/E795).…”