The cleidoatlanticus muscle: a potential pitfall for the practice of ultrasound guided interscalene brachial plexus block

Abstract

As this muscle crosses at a level, where ultrasound guided interscalene blocks are performed, this unusual structure might lead to misinterpretation of the confusing ultrasound image, resulting in misguided needle positioning and consecutive inefficiency of the block technique.

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

“…Integrating the hypotheses proposed by McKenzie and Giebel, it is plausible that the myotome is destined to be part of the SCM-TZ and the levator scapulae divides into a discrete muscle bundle (i.e., the levator claviculae). This idea seems to reconcile with other cases where the levator claviculae directly originated from the trapezius (O’Sullivan and Kay 1998) and from the sternocleidomastoid (Feigl and Pixner 2011). Moreover, this connection between the cervical myotome and the brachiogenic trapezius and sternocleidomastoid might explain why these two neck muscles derived from the brachial arch have two sources of innervation: spinal nerves and the accessory nerve (McKenzie 1955).…”

“…As a rule, the levator claviculae inserts onto the middle or lateral clavicle. However, insertion onto the sternocleidomastoid (Feigl and Pixner 2011) and the serratus anterior (Flower and Murie 1867) has been noted.…”

“…In the clinic, the levator claviculae has the potential to be misidentified as a cyst, an arterial aneurysm, a neurofibroma, metastasis, a lymphadenopathy (Rüdisüli 1995; Rosenheimer et al 2000), the sternocleidomastoid (Feigl and Pixner 2011), or a thrombosed vein (Rubinstein et al 1999) in imaging diagnostics. From another standpoint, the levator claviculae has the potential to cause thoracic outlet syndrome, a rare condition that involves compression at the superior thoracic outlet, leading to pain, arm discoloration, and tingling, among other symptoms (Aydoğ et al 2007).…”

“…It usually originates from the transverse process of the upper cervical vertebrae, and attaches to the lateral aspect of the clavicle (Eisler 1912; Koshy et al 2005). While some articles in the literature have reported a tendency of this muscle to appear on the left side (Rubinstein et al 1999; Capo and Spinner 2007), this is not a strict rule (Holibková and Machálek 1998; Feigl and Pixner 2011). In primates other than humans (Gibbs et al 2002), this muscle is always present bilaterally.…”

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.…”