Anatomical relationships of the cleidoatlanticus muscle. Interpretation about its origin

Abstract

An unusual muscular variation, the cleidoatlanticus muscle, was observed on the right-hand side of the lateral cervical region. The upper third of the muscle was concealed by the sternocleidomastoid muscle. There was a loop of nerves surrounding the muscle, formed by an anastomosis between the transverse cervical nerve and the greater auricular nerve. A fine vascular-nervous pedicle (formed by a small branch from the transverse cervical artery and by a branch from the medial supraclavicular nerve) entered the deep surface of the muscle at the junction of its middle and lower thirds. Taking into account the relationships that presented with the superficial branches of the cervical plexus, we consider that the cleidoatlanticus muscle is derived from the sternocleidomastoid muscle.

Bilateral Supernumerary Sternocleidomastoid Heads with Critical Narrowing of the Minor and Major Supraclavicular Fossae: Clinical and Surgical Implications

“…Its frequency is estimated to be 1-3% (Fasel et al, 1994), but probably it is even lower as judged by the very few reports in the literature (Tomo et al, 1994). When the muscle terminates on the transverse process of the atlas it is termed as cleidoatlanticus muscle, which is a very rare variant with only four reports in the literature (Grüber, 1876;Koshy et al, 2005;Rodríguez-Vázquez et al, 2009;Feigl & Pixner, 2011). However, it may be difficult to distinguish if an observed tendon is inserted or emerges from a given structure in the cadaver accounting for problems in the determination of cleidoatlanticus and levator claviculae muscle, which macroscopically may look very similar but has a contrariwise function.…”

Anatomy of the levator claviculae, with an overview and a literature survey

“…There are six other candidate muscles proposed hitherto: sternocleidomastoid (Rodríguez-Vázquez et al 2009); trapezius (Parsons 1898); sternocleidomastoid and trapezius (Fasel et al 1994; Holibková and Machálek 1998); LCO (Tomo et al 1994); ventrolateral muscle primordium of the neck, viz. the scalene, anterior vertebral muscles and infrahyoid muscles (Leon et al 1995; Koshy et al 2005); and anterior scalene (Theile 1843; Gruber 1876).…”

“…the scalene, anterior vertebral muscles and infrahyoid muscles (Leon et al 1995; Koshy et al 2005); and anterior scalene (Theile 1843; Gruber 1876). Rodríguez-Vázquez et al (2009) defined the origin of the levator claviculae as the sternocleidomastoid from their observation. According to their assumption, the great auricular nerve and the transverse cervical nerve, which existed between the two muscles in their case, caused the separation of the levator claviculae from the anlage of the sternocleidomastoid.…”

“…For example, a variety of names have been assigned to this muscle, chiefly according to their origin and insertion: the cleidoatlanticus (Rodríguez-Vázquez et al 2009), the acromio-trachélien (Gruber 1876), the omo-cleido-transversarius (Giebel 1874), the omocervicalis (McKenzie 1955), the atlantoscapularis anterior (Kajiyama 1970), the cleido-cervicalis (Gruber 1876), the cléido-omo-transversaire (Testut 1884), and the omo-trachelian (Parsons 1898). Quite confusingly, these synonyms are often used interchangeably in various contexts.…”

“…In primates other than humans (Gibbs et al 2002), this muscle is always present bilaterally. Although the nerve supply usually comes from the cervical plexus, we do not know exactly which nerve branch innervates this muscle (Rodríguez-Vázquez et al 2009). There are currently some hypotheses concerning its embryological origin: sternocleidomastoid (Rodríguez-Vázquez et al 2009), trapezius (Parsons 1898), ventrolateral muscle primordium of the neck (Leon et al 1995), anterior scalene (Gruber 1876), and longus colli (LCO) (Tomo et al 1994).…”