Variation of the sternocleidomastoid muscle: a case report of three heads and an accessory head

Abstract

Purpose Anatomical variations of the sternocleidomastoid muscle (SCM) have been observed to occupy multiple origins and insertion points and have supernumerary heads, sometimes varying in thickness. Methods An 85-year-old Korean male cadaver was dissected and a SMC with unilateral supernumerary heads was identified. Results Three heads and an accessory belly of the sternal head were recorded on the left side. There were two clavicular heads, one lateral and one medial. The sternal head originated inferior to the manubrium of the sternum. A small belly arose from the sternal head and merged to the lateral clavicular head on the C5 vertebrae level. These bellies inserted into the mastoid process of the temporal bone. Conclusions These variants may be problematic during surgical approaches to the upper neck and occipital, and should thus be appreciated by the clinician.

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).…”

An Accessory Muscle Originating From the Hyoid Bone and Inserting Into the Sternocleidomastoid Muscle

“…Before the intervention, knowledge of anatomic variations is paramount for every surgeon as it might prevent severe complications. Irregular bellies and insertions into neck muscles have been described in the literature [1][2][3][4][5]. To the best of our knowledge, a right accessory muscle originating from the hyoid bone and inserting into the sternocleidomastoid muscle has not been reported to date.…”

Sternocleidomastoid muscle can have multiple attachments

“…We read the article entitled "Variation of the sternocleidomastoid muscle: a case report of three heads and an accessory head" [2] published your esteemed journal. The authors of the article have reported a muscle with three heads of origin and an accessory head.…”