Cleidocervical muscle: a mini literature survey of a human muscle variation.

Cleidocervical muscles (CCM) or levator claviculae muscles in humans can be found as supernumerary unilaterally or bilaterally on the neck attached proximally to the clavicle and distally to the transverse process of cervical vertebrae at various levels. Altogether 20 case reports from year 1994 till present including 25 subjects related to CCM were found and analysed where parameters such as cervical insertion level, clavicular insertion at the middle vs. lateral third, unilateral vs. bilateral presence of the muscle, study type, reported gender of the subjects were extracted. Our literature survey shows that the prevalence of CCM in male and female was equally presented in radiological studies whereas almost 3-fold higher prevalence of males was found in cadaver reports. Since body donor system worldwide is male dominant, a 1:1 proportion of male and female in radiological studies could show more reality-based distribution of this muscle. Nevertheless, the presentation of this muscle was found in over 90% of the case reports unilaterally with higher left sided dominance. Even though the attachment points of CCM varied from case to case, the proximal attachment was found slightly more frequent on the middle third of the clavicle whereas the distal insertion was present more often on the superior cervical vertebrae than the lower ones. With prevalence of CCM in the population around 2.0-2.5%, the clinical, radiological and surgical relevance of this variation has to be highlighted to avoid potential misleading diagnostics in the neck.