SHORT REPORT Eur J Anat, 9 (2): 103-106 (2005) Supernumerary cleidocervicalis (levator claviculae) muscle: case report of its rare inci- dence with clinical and embryological significance S. Koshy, S. Rabi and I. Indrasingh Department of Anatomy, Christian Medical College, Vellore, India SUMMARY et al., 1995). Its incidence is reported to be 2- 3% (Wood, 1869; Macalister, 1875; Gruber, During routine dissection by medical students at 1876; Testut, 1894; Le Double, 1897; Rubinstein the Department of Anatomy of the posterior et al., 1999). Variants of this muscle have been triangle of the neck of a South Indian muscular described as having different combinations of male cadaver, aged 67 years, a variant of the rare origins, ranging from transverse processes of supernumerary cleidocervicalis muscle was the cervical vertebrae to insertions to the clavi- found bilaterally. This muscle arose from the cle, the nerve supply, and sidedness: an origin transverse processes of the atlas and axis. It ter- from the transverse process of the sixth cervi- minated by inserting into the posterior aspect of cal (Tomo et al., 1994; Rosenheimer et al., the lateral third of the clavicle, merging with the 2000), first cervical (Leon et al., 1995), or first anterior fibres of the trapezius muscle. It was and second cervical vertebrae (Holibkova and innervated by branches from the second, third, Machalek, 1998), or the upper part of the cer- and fourth cervical nerves. No variation was vical vertebral column (Fasel et al., 1994; noted in the other muscles in this region. The Rubinstein et al., 1999); insertion into the supe- present report addresses another variant of the rior margin (Tomo et al., 1994), the posterior cleidocervicalis muscle with a combination of aspect of middle third (Leon et al.,, 1995; origin, insertion, and nerve supply different from Rubinstein et al., 1999), or the lateral third most previous reports. The aim of the present (Holibkova and Machalek, 1998; Rubinstein et case report is to highlight its clinical significance al., 1999) of the clavicle, nerve supply from the to physicians, surgeons, and radiologists in order fifth (Tomo et al., 1994), fourth (Leon et al., to differentiate it from other soft tissue lesions, 1995), or second to fourth (Holibkova and together with its embryological significance to Machalek, 1998) cervical nerves; and location anatomists. unilaterally on the left-side (Tomo et al., 1994; Rudisuli, 1995; Fasel et al., 1994; Rubinstein et Key words: Cleidocervicalis muscle – Levator al., 1999; Shaw and Connor, 2004), unilaterally claviculae muscle – Soft-tissue lesion – Supernu- on the right-side (Leon et al., 1995; Rubinstein merary muscle et al., 1999), or bilaterally (Nagashima et al., 1989; Rubinstein et al., 1999). A cleidocervica- lis muscle has not been reported in Indian sub- INTRODUCTION jects. The aim of the present case report on the cleidocervicalis muscle is to highlight its clini- The cleidocervicalis or levator claviculae is a cal significance to physicians, surgeons, and supernumerary muscle situated in the posterior radiologists in order to differentiate it from triangle of the neck (Kelch, 1813; Gruber, 1876; other soft tissue lesions, together with its embr- Nagashima et al., 1989; Tomo et al., 1994; Leon yological significance for anatomists. Correspondence to: Submitted: March 14, 2005 Dr. Shajan Koshy. Department of Anatomy, Christian Medical College, Vellore 632 002, India. Accepted: July 8, 2005 Phone: 0416 - 2284245 / Fax: 0091 - 416 - 2262788. E-mail: [email protected] 103 S. Koshy, S. Rabi and I. Indrasingh RESULTS et al., 2000). An unusual variant of the cleido- cervicalis muscle was encountered during explo- During routine dissection of the posterior trian- ratory surgery of the brachial plexus (O’Sullivan gle of the neck by medical students at the and Kay, 1998). When this muscle is encounte- Department of Anatomy on a 67-year old South red during explorations in the posterior triangle, Indian muscular male cadaver, a variant of the it may be safely resected since it is vestigial. The rare supernumerary cleidocervicalis muscle (Fig. cleidocervicalis muscle has been identified on 1) was found bilaterally. This muscle had a cylin- CT scans, which presented clinically as head and drical belly and measured 12.5 x 2.4 cm. The neck cancer or multiple enlarged lymph nodes muscle arose by a rounded tendon from the (Rudisuli, 1995). A soft tissue shadow seen transverse processes of the atlas and axis. The during routine radiological examination can be muscle ran parallel to the origin of the levator identified as a cleidocervicalis muscle by three- scapulae. It terminated by inserting into the pos- dimensional reconstruction, and hence reinfor- terior aspect of the lateral third of the clavicle, ces the significance of identifying muscular merging with the anterior fibres of the trapezius variants by modern imaging techniques (Fasel et muscle. The upper third of this cleidocervicalis al., 1994). Multiplanar reformation of a mimicked muscle was covered by the sternocleidomastoid. cervical lymph node enlargement at preoperati- It was superficial to the omohyoid, scalenus ve axial computed tomography was confirmed anterior, and scalenus medius muscles. It had its as the muscle, which had a shape ranging from own fascial sheath, derived from the deep cervi- rounded to linear, changing shape along its cal fascia. The internal jugular vein was deep to length. Radiologically, it may be confused with the belly of the cleidocervicalis muscle. In the lymphadenopathy, leading to inappropriate lower part, the muscle was superficial to the management (Shaw and Connor, 2004). The superficial cervical and suprascapular arteries, importance of the cleidocervicalis muscle to phrenic nerve, and ventral branches from the radiologists lies in distinguishing it from an second, third, and fourth cervical nerves before abnormality; most commonly cervical adeno- they formed the large auricular, transverse cervi- pathy using CT scans (Rubinstein et al., 1999). A cal and supraclavicular nerves. The cleidocervi- posterior cervical space mass was identified on calis muscle was innervated by branches from CT as a cleidocervicalis muscle. Radiologists are the second, third, and fourth cervical nerves (Fig. thus cautioned to become familiar with the clei- 2): the upper third of the muscle by branches docervicalis muscle and its appearance in order directly from the roots of the anterior rami of to avoid misdiagnosing it as pathologic (Gins- second and third cervical nerves, and the lower berg and Eicher, 1999). Since the cleidocervicalis two thirds by branches from the loop between muscle is situated superficially in the posterior the third and fourth cervical nerves. No variation triangle of the neck, it overlies a number of small was noted with the other muscles in this region. arteries and nerves. It may therefore press on any of these structures and cause compression syndromes. DISCUSSION The cleidocervicalis muscle has more embryo- logical than functional significance. It appears The cleidocervicalis (levator claviculae) muscle is regularly in the neck of all anthropoid apes (Tes- a supernumerary (i.e., more than the usual, extra) tut, 1894; Le Double, 1897) and most other mam- muscle in the posterior triangle of the neck. It is mals (Parsons, 1898; Aiello and Dean, 1990; a vestigial muscle and is an infrequently recogni- Rubinstein et al., 1999) but has been lost in zed variant in humans. It is a relatively uncom- modern man. It is considered to have originated mon and little reported normal variant. Variants of from the scalene muscles (Kelch, 1813; Gruber, this muscle have been reported. The present 1876), sternocleidomastoid (Wood, 1869), trape- report describes another variant of the cleidocer- zius (Parsons, 1898), both of which develop from vicalis muscle with a combination of origin, inser- the material of post-branchial arches (caudal divi- tion, and nerve supply different from most pre- sion of the branchiogenic muscles) and cervical vious reports but closely resembling that of somites (Lewis, 1910; McKenzie, 1962; Holibkova Holibkova and Machalek (1998). and Machalek, 1998), both the inferior hyoid and The unexpected rare incidence of the cleido- sternocleidomastoid muscles (Nagashima et al., cervicalis muscle is of clinical significance. It can 1989), scalenus anterior, longus capitis, or the lon- present as a hard mass in the clavicular area gus coli, most likely the longus coli (Tomo et al., associated with an angular deformity of the cla- 1994). The embryological origin of the cleidocer- vicle (Santiago et al., 2001). During routine phy- vicalis muscle is possibly from the ventrolateral sical examination, a palpable soft tissue was muscle primordia of the neck, which in addition to observed and with further imaging techniques it contributing to the formation of the anterior verte- was identified as the cleidocervicalis muscle. bral, hyoid, and scalene muscles (Lewis, 1910; This observation underscores the importance of Arey, 1965), also contribute to the formation of a understanding soft tissue variants (Rosenheimer new muscle with an ‘atavistic’ character through a 104 Supernumerary cleidocervicalis (levator claviculae) muscle: case report of its rare incidence with clinical and embryological significance Fig. 1.- Cleidocervicalis muscle in the left posterior triangle of the neck. SCM - Sternoleidomastod muscle; T - Trapezius muscle; CC - CLeidocervicalis muscle; o - Omohyoid muscle.