The Levator Claviculae muscle presenting as a neck mass.
The levator claviculae muscle in humans represents an uncommon muscular variation located with in the posterior triangle of the neck. First described nearly 145 years ago, (1) the incidence of this muscle is reported to be 1% to 2%.12 In contrast to the human species, the muscle is unequivocally and normally found in lower mammals. (1) The characteristic course of this supernumerary muscle as demonstrated by CT and MR makes the diagnosis certain. Recognition as a normal variant is therefore important to radiologists and surgeons in order to prevent misdiagnosis as lymphadenopathy, thrombosed vein or other soft-tissue mass.
A 14 year old male presented to his primary care physician with a palpable neck mass. The nontender and nonmobile mass was located in the left mid and lower neck, superior to the clavicle and posterior to the sternocleidomastoid muscle. The patient complained of no fever, additional masses, history of prior malignancy or other clinical symptoms. Evaluation by CT with intravenous contrast revealed the characteristic course of the anomalous muscle with no adenopathy or mass (Figure 1 and Figure 2).
The levator claviculae muscle in humans represents a rare cervical muscular variant. Approximately 30 reports detailing the levator claviculae in humans have been documented in the past 170 years. (3) However, after reviewing 300 CT scans, Rubinstein found the frequency of the muscle to be 2%, indeed similar to the frequency reported more than a century ago by Wood. (1,2) The embryologic origin of the muscle remains a controversial issue. Several hypotheses for the origin of the levator scapulae propose the sternocleidomastoid, trapezius, scalenus anterior, longus coli or ventrolateral muscle primordial of the neck as the embryologic derivative. (4)
The origin and insertion of the levator claviculae vary greatly among species; however, in humans the muscle frequently arises from the transverse processes of the cervical spine and inserts onto the middle or lateral clavicle. Typically arising from the transverse process of C3 to C5, the levator claviculae courses inferiorly, lateral to the scalene and levator scapulae muscles, medial and posterior to the sternocleidomastoid muscle and usually inserting on the clavicle. Most commonly the muscle inserts onto the middle or lateral clavicle. However, insertion sites may vary and include the medial clavicle as well as the sternocleidomastoid and serratus anterior muscles. (5,6) The exact insertion site may be difficult or impossible to adequately determine. Elevation of the clavicle and lateral flexion of the neck are generally regarded as the function of the muscle.
The levator claviculae muscle is frequently asymptomatic and usually discovered by CT and MR as an incidental finding. However, the muscle may present as a mass and misinterpreted clinically as a thrombosed vessel, cyst, lymph node or neoplasm. (5-8) In addition, thoracic outlet syndrome in a gymnast has been reported as a complication of this muscle. (9) The levator claviculae may be bilateral or unilateral. When the muscle occurs unilaterally, it is more frequently encountered on the left. (2)
The levator claviculae is an uncommon muscular variation. Its origin and insertion are varied. However, given the typical course of the muscle demonstrated by CT and MR, recognition of the levator claviculae will allow the radiologist to accurately define the variant and prevent misinterpretation as a pathologic lesion.
(1.) Wood J. On a group of varieties of the muscles of the human neck, shoulder, and chest with their transitional forms and homologies in the mammalia. Philos Trans R Soc London 1870; 160:83-116
(2.) Rubinstein D, Escott E, Hendrick L. The Prevalence and CT Appearance of the Levator Claviculae Muscle: A Normal Variant Not To Be Mistaken for an Abnormality. J Neuroradiol 1999, 20:583-586.
(3.) Toru O, Masataka K, Kazuki I, Satoshi F, Haruo F, Sen T. Anatomy of the levator claviculae, with an overview and a literature survey. Anatomical Science International Dec 2012; 87(4):203-211
(4.) Leon X, Maranillo E, Quer M, Sanudo J. Case report: cleidocervical or levator claviculae muscle. A new embryological explanation as to its origin. J Anat 1995; 187:503-504
(5.) Feigl G, Pixner T. The cleidoatlanticus muscle: a potential pitfall for the practice of ultrasound guided interscalene brachial plexus block. Surg Radiol Anat. 2011; 33(9):823-825.
(6.) Parsons F. The muscles of mammals, with special relation to human myology. J Anat Physiol. 1898; 32:428-450.
(7.) Ginsber L, Eicher S. Levator claviculae muscle presenting as a neck mass: CT imaging. J ComputAssist Tomogr 1999; 23: 538-539.
(8.) Santiago R, Milena L, Milena L, Santos C, Fernadez T. Levator claviculae muscle presenting as a hard clavicular mass: imaging study. Eur Radiol 2001; 11:2561- 2563
(9.) Aydog S, Ozgakar L, Demiryurek D, Bayramoglu A, Yorubulut M. An intervening thoracic outlet syndrome in a gymnast with levator claviculae muscle. Clin J Sport Med 2007; 17:323-325.
Haley C. Schlarb, MSII
West Virginia School of Osteopathic Medicine
Daniel W.Williams, MD
Department of Radiology, Wake Forest University--Baptist Health
Alexander C. Schlarb
West Virginia School of Medicine
Rudy Judhan, MD
Department of Surgery, West Virginia University--Charleston Division
Christopher A. Schlarb, MD
Department of Radiology, West Virginia University--Charleston Division
Corresponding Author: Christopher Schlarb, MD, 12 Dunlevy Rd., Charleston, WV 25314. Email: cschlarb@ suddenlink.net.
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|Title Annotation:||Case Report|
|Author:||Schlarb, Haley C.; Williams, Daniel W.; Schlarb, Alexander C.; Judhan, Rudy; Schlarb, Christopher A.|
|Publication:||West Virginia Medical Journal|
|Article Type:||Case study|
|Date:||Mar 1, 2016|
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