Muscular Variation in the Neck Region with Narrowing of the Minor and Major Supraclavicular Fossa ORIGINAL

International International Archives of Medicine 2017 Medical Society Section: Human Anatomy Vol. 10 No. 208 http://imedicalsociety.org ISSN: 1755-7682 doi: 10.3823/2478

Humberto Ferreira Abstract Arquez1

Background: The sternocleidomastoideus muscle is the most promi- 1 University of Cartagena. University nent landmarks of the surface anatomy of the neck, separates the an- St. Thomas. Professor Human terior part of the neck (anterior triangle) from the posterior part of the Morphology, Medicine Program, neck (posterior triangle). An accessory head of sternocleidomastoideus University of Pamplona. Morphology Laboratory Coordinator- University of muscle may cause complications while trying to access vital neurovas- Pamplona cular structures that are located in the minor and major supraclavicular fossa. The purpose of this study is to describe an anatomical variation Contact information: of the sternocleidomastoideus muscle and clinical impact. Humberto Ferreira Arquez Methods and Findings: The anatomical variations described were Address: University Campus. Kilometer, found during routine dissection conducted in the laboratory of Mor- 1. Via Bucaramanga. phology of the University of Pamplona in two male cadavers of 47 Tel: 75685667-3124379606. and 75 years respectively. Measurements were taken using a Vernier caliper. Topographic details of the variations were examined, recorded  [email protected] and photographed. The morphological variations in the number of heads (three and four) of origin of sternocleidomastoideus muscle was found in two male subjects in right and left neck, bilaterally. The posterior cervical triangle was diminished. The bilateral narrowing of Keywords the minor and major supraclavicular fossa minimizing space needed Anatomical Variation, for potential surgical access. The branching patterns of the spinal ac- Clavicular Head, Sternal cessory nerve and arterial patterns were normal. Head, Minor Supraclavicular Fossa, Major Supraclavicular Conclusions: The Knowledge of the presence of additional heads of Fossa, Additional Head, sternocleidomastoideus muscle it might cause difficulties in subclavian Sternocleidomastoideus or external jugular vein catheterization, and in surgical interventions Muscle, involving structures lying under the sternocleidomastoideus muscle. Sternocleidomastoideus These variations must be kept in mind while approaching the region Syndrome. to avoid complications as the classical anatomical landmarks might be misinterpreted and confuse.

© Under License of Creative Commons Attribution 3.0 License This article is available at: www.intarchmed.com and www.medbrary.com 1 International Archives of Medicine 2017 Section: Human Anatomy Vol. 10 No. 208 ISSN: 1755-7682 doi: 10.3823/2478

Introduction domastoideus functions as landmark for physicians, The muscles of the neck generate head movements surgeons and anesthesiologists, who intervene in and maintain the stability of the cervical spine; the minor supraclavicular and major supraclavicu- Sternocleidomastoideus (SCM) muscle plays a ma- lar fossa. The variability of sternocleidomastoideus jor part in it. The SCM muscle is one of the most anatomy may cause complications while trying to complex in the body. It functions as a short range access vital structures located in the fossa [5]. Any (clavicular head) and long range (sternal head) ro- variation in origin of Sternocleidomastoideus mus- tator, an upper cervical extensor, a flexor of the cle can lead to narrowing of minor supraclavicular cervical spine on the thoracic spine, a lateral flexor, fossa, which can complicate internal jugular vein, as well as a very important source of equilibrium sublavian vein, external jugular vein cannulation. A [1,2]. In classic anatomical description, the sternal myocutaneous flap including an additional head of and clavicular portions of SCM muscle represent its sternocleidomastoideus is of great use to the plas- origins, both the heads blends below the middle of tic surgeon because of its adequate vascularity and the neck, leaving a changeable space in between presence of sufficient tissue to be transferred to the them and the clavicular portion varies sufficiently recipient site [1-5]. The presence of supernumerary in width. The muscle is inserted then in the lateral heads of SCM may affect the usual mechanism of surface of the mastoid process and the lateral half a clavicle fracture and have a direct effect on bone or the two third part of the superior nuchal line, in fragments, diagnoses and treatment; malunion may the occipital bone [1]. impair these functions, in addition, callus formation The SCM muscle is responsible for the mechanical or displacement can lead to thoracic outlet com- action in the majority of the head movements, is pression. The accessory SCM muscle could mimic also considered an accessory muscle for respiration. pathological masses of the lateral neck region and The sternocleidomastoideus muscle is situated on can be confused with soft tissue masses such as the side of the neck. This thick muscle protects the lymphadenopathies; on clinical and imaging studies great vessels, the branches of the cervical plexus, including metastatic disease, or benign tumors such deep cervical lymph nodes and soft tissues from as cyst, glomus tumor, neurofibroma, thrombosed damage. The sternocleidomastoideus muscle is vein, hematoma, familiar sternocleidomastoideus tu- supplied by the spinal part of the accessory nerve. mor of infancy, and hypertrophy of the SCM [2,6,7]. It also receives proprioceptive innervations by cer- The objective of this study was to describe an ana- vical spinal nerves from the cervical plexus [2]. The tomical variation of bilateral sternocleidomastoideus sternocleidomastoideus muscle receives its blood anatomy, the morphology features, the prevalence supply from branches of the occipital and posterior and clinical impact. auricular arteries, which supply the upper part of the muscle. The muscular branches coming from the superior thyroid artery and suprascapular ar- Methods tery supply the middle and lower part of sterno- This work was previously approved by the Ethics cleidomastoideus muscle [2-4]. The two heads of Committee in Research and Environmental Impact sternocleidomastoideus form with clavicle, the mi- of the University of Pamplona, conformed by reso- nor supraclavicular fossa. The major supraclavicular lution 030 of January 16 of 2014 and Resolution fossa is a larger depression behind the intermediate No. 008430 of 1993 of October 4 of the Ministry 3rd of the clavicle, between the lower parts of tra- of Health of Republic of Colombia by which regula- pezius and sternocleidomastoideus. The sternoclei- tes the scientific, technical and administrative norms

2 This article is available at: www.intarchmed.com and www.medbrary.com International Archives of Medicine 2017 Section: Human Anatomy Vol. 10 No. 208 ISSN: 1755-7682 doi: 10.3823/2478

for health research. This descriptive cross-over study fibers at a distance of 4.8 cm from the clavicle, was designed to determine the prevalence, mor- while the distance of fusion of additional clavicular phologic features and anatomical variations of the fibers with the usual clavicular fibers was 5.3 cm. sternocleidomastoideus muscle. The region neck The sternal, usual clavicular and additional clavicular were studied serially during the years 2014-2016 in heads were blending into a thick, rounded muscle 15 male and 2 females embalmed adults cadavers belly which was inserted by a tendon onto the late- in the laboratory of Morphology of the University ral surface of the mastoid process and the superior of Pamplona. The anatomical variations described nuchal line of the occipital bone. Medial minor were found during routine dissection conducted in supraclavicular fossa: the depression was between the laboratory of Morphology of the University of 1st and 2nd heads, base about 1.5 cm and height Pamplona in two male cadavers of 47 and 75 years of about 4.5 cms on either side. Internal jugular vein respectively. Measurements were taken with assis- was found behind the second head. Lateral minor tance of a sliding Vernier caliper, accurate to 1 mm supraclavicular fossa: the depression was between during the course of the anatomical dissection. The 2nd and 3rd heads, base about 0.8 cm and height data thus obtained were recorded in a physical ma- of about 3.6 cms on either side. Spinal accessory trix and were consigned in digital media using Excel nerve was found between 1st and 3rd heads pre- tables. Topographic details of the variations were sent superficially and 2nd head on its deeper aspect examined, recorded and photographed. and supplied the three heads. The usual as well as the additional slip were supplied by a branch from the spinal part of the accessory nerve. The additio- Results nal head received its blood supply from an inde- The morphological variations in the number of pendent branch of suprascapular artery (Figure 1). heads of origin of sternocleidomastoideus muscle In the same male cadaver of 47 years old, on the were observed in 2 out de 16 neck (11.76%). It was left side, instead of a normal sternocleidomastoideus found in two male subjects in right and left neck, (SCM), four muscle bellies were recorded, in terms bilaterally. The remaining 15 neck (88.24%) showed of heads one sternal and three clavicular. The me- the normal origin, insertion, course of the sterno- dial of the four heads had anatomy corresponding cleidomastoideus and the course and branching to the usual sternomastoid portion of the SCM. It patterns of the spinal accessory nerve and arterial was extended from the sternal manubrium to the patterns was normal having classic branching. mastoid process tip. The second head extending In the male cadaver of 47 years old in the right from the sternoclavicular joint, posterior and late- side, it was observed that the sternocleidomastoi- ral to the origin of the sternomastoid muscle. The deus muscle has three heads, arising by a tendinous third muscle head originated from the lateral part head from the front of the manubrium sterni and of the proximal third of the clavicle and terminated by a broad aponeurotic head from the medial part at the occipital bone just inferior to the insertion of the upper surface of clavicle, lateral to its medial of the sternomastoid head. A fourth muscle head, end. Additionally, an unusual prominent and broad arose from the middle third of the clavicle, cour- muscular slip was also arising from the upper sur- sed upwards, posteriorly, and obliquely, in a parallel face of clavicle, lateral to its medial end. The fibers course to the previously described muscle bellies and of both the clavicular heads were directed vertically fused with the third head muscle at the level of the upwards and backwards. The fibers of the usual or middle third of the anterior border of the trapezoid medial clavicular head were fusing with the sternal muscle. The non-typical arrangement of the muscle

found between 1st and 3rd heads on the superfi- Figure 1: Superficial dissection of right side of cial aspect and 2nd and 4th heads on the deeper the neck region showing three heads of aspect and supplied the four heads. The additional sternocleidomastoideus muscle. head received its blood supply from an independent branch of suprascapular artery. (Figure 2). The presence of third head or accessory head of Sternocleidomastoideus was observed bilaterally in a male cadaver of 75 years of age: Right Sternocleidomastoideus, it had three heads, sternal head had a rounded origin from anterior surface of the manubrium sterni, got inserted to the mastoid process and s