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International Journal of Morphology

versão On-line ISSN 0717-9502

Int. J. Morphol. v.21 n.4 Temuco  2003 

Int. J. Morphol., 21(4):261-264, 2003.



*Boaro, Sueli Nicolau & **Fragoso Neto, Raul Antonio

BOARO, S. N. & FRAGOSO NETO, R. A. Topographic variation of the sternocleidomastoid muscle in a just been born children. Int. J. Morphol., 21(4):261-264, 2003.

SUMMARY: The sternocleidomastoid muscle was dissected in one just been born children with approximately nine months of age. The topographic variation of this muscle found in this work suggests your surgical importance and your influence in the appropriate surgical access to repair structures found in the neck.

KEY WORDS: 1. Sternocleidomastoid muscle; 2. Neck; 3. Anatomical variation.


The sternocleidomastoid muscle is responsible for the mechanical action in the majority of the head movements, is also considered an accessory muscle for respiration (Costa et al., 1994). This muscle binds the skull to the clavicle and the breastbone. It is the most prominent muscle of the anterior and posterior triangular areas. When the sternocleidomastoid muscle is strongly contracted, it is possible to observe a clavicular and other sternal insertion. It arises on the top in the mastoid process and in the superior nape line of the occipital bone. It goes down, frontwards and lightly medially, to finish in the manubrium breastbone and sternal portion of the clavicle, where the tendons of the two sternocleidomastoid muscles (one at each side) delimited the sternal fork Calais-German (1992). In classic anatomical literature, the sternal and clavicular portions of sternocleidomastoid muscle represent its origins, meet moved away by a changeable space and the clavicular portion varies sufficiently in width. The muscle is inserted then in the lateral surface of the mastoid process and in the lateral half or the two third part of the superior line of the nape of the neck, in the occipital bone (Gardner, 1988). The present work sample that is necessary the knowledge of the anatomical variations in muscles of the neck, as they certify the some specific works in the area, related supernumerary muscular beams (Grüber, 1885; Miyauchi, 1983), muscular anomalies (Miyauchi; Richet,1873) or the variability of the sternocleidomastoid muscle (Demir et al., 1994; Koura,1959; Krause, 1876; Mori, 1964; Ouchi, 1953; Shima & Ichikawa, 1956). In addition to these, there are reports with reference to the clavicular origin of the sternocleidomastoideus, it was subdivided occasionally into several slips, separated by narrows intervals (Gray, 1918; 1977).


The specimen duly was fixed with formaldehyde 10%. In a routine dissection, under a surgical microscope, it was observed in a nine months old baby, a clavicular arrangement of the insertion of the sternocleidomastoid muscle. The skin, the platisma muscle (Fig. 1a), muscular fascia, veins and superficial nerves (Fig. 1b ­ c) were take away with the use of a bistoury to evidence the sternocleidomastoid muscle. After macroscopic examination of the muscle it was observed that just in one specimen presented the variation muscular in your attachment.

Fig. 1. Photography showing the sequence of dissection of the neck. a ­ Platism muscle (arrow). b ­ Sternocleidomastoid (S) and trapezius (T) muscles. c ­ Sternocleidomastoid muscle (S) with nerves and vein crossing this muscle. d ­ Vatiation of the sternocleidomastoid muscle (S). This muscle has four attachments (1,2,3,4).


The sternocleido-mastoid muscle after gross dissection showed morpho-logic variation. Macrosco-pically, the muscle showed four portions arranged in two layers, superficial and deep one. The first layer consisted in one sternal head by means of a long tendon from the manubrium breastbone, as well as in one clavicular head, like a short tendon from the sternal part of clavicle. The third portion of this layer was represented by another clavicular head, attached in the acromial part of this bone (Fig. 1d). The second layer was represented by one single voluminous clavicular head, situated between the both clavicular heads previously described. Before they inserted in the mastoid process, the two above-mentioned layers fused along the lateral region of the neck (Fig. 1d).


Comparative anatomical studies related the Man had concluded that the sternocleidomastoid muscle is formed by five portions arranged in two layers. In our report, we observed just four portions. The amount of fusion the two heads of this muscle varies considerably.

In 88,6% of japanese subjects (450/510 individuals), the two heads (sternal and clavicular) of this muscle are independent or distinct. In these citizens, the space between the two heads is triangular and filled with fascia, and named Trigonum supraclavicularis minor and covered by cervical fascia (Mori).

The observed anatomical variation in the present work has practical interest since surgical access to the various structures of the neck always makes uses of the arrangement of the musculature and other structures delimited by the borders. Variations in muscle arrangement at the base of neck could therefore result in inadequate repair of the important structures in this area, like the vascular and nervous structures of the neck root.

Recently, radiological parameters have been outlined to identify boundaries between various neck levels among them the sternocleidomastoid muscle (Hamoir et al., 2002).

In patients with irradiation-induced cervical muscle spasm benefit from treatment with botulinum toxin A injections (van Daele et al., 2002). Would the patients with painful tightness of the neck who received botulinum toxin A injections to the sternocleidomastoid muscle achieved pain relief need a larger dose of the toxin, due to variation of the sternocleido-mastoid muscle found in this work.

In face of these ranks, the proposal of the present work more justifies the continuation of deepened morphologic studies on the variability of the muscle in appraises in the experimental clinical research.


To the Professor Doctor João Adolfo Caldas Navarro for yielding the corpse of the just-been born child. In memory.

BOARO, S. N. & FRAGOSO NETO, R. A. Variación topográfica del músculo esternocleidomastoídeo en un niño recién nacido. Int. J. Morphol., 21(4):261-264, 2003.

RESUMEN: El músculo esternocleidomastoídeo fue disecado en niño de, aproximadamente, nueve meses de edad. La variación topográfica de este músculo tiene importancia clínica y quirúrgica, principalmente en el acceso quirúrgico al cuello con la finalidad de reparar estructuras de esa región.

PALABRAS CLAVE: 1.Músculo esternocleidomastídeo, 2.Cuello, 3. Variación anatómica.


Calais-German, B. Anatomia para o movimento. In: Os músculos anteriores e laterais do pescoço. São Paulo, Manole, 1992. V. 1. pp. 84-8.

Costa, D.; Vitti, M.; Oliveira, D. T. & Costa, R.P. Participation of the sternocleidomastoid muscle on deep inspiration in man. An electromyographic study. Electromyogr. Clin. Neurophysiol., 34:315-20, 1994.

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Correspondence to:
Prof. Dra. Sueli Nicolau Boaro
Departmen of Physical Education
Faculty of Sciences and Technology
Paulista State University «Júlio de Mesquita Filho» UNESP
Rua Roberto Simonsen 305
CEP 19060-900
Presidente Prudente - SP


Received : 17-07-2003
Accepted : 28-08-2003

* Department of Physical Education, of Faculty of Sciences and Technology, Paulista State University "Júlio de Mesquita Filho" (UNESP), Presidente Prudente, SP, Brazil.

** Department of Physiotheraphy of Faculty of Sciences and Technology, Paulista State University "Júlio de Mesquita Filho" (UNESP), Presidente Prudente, SP, Brazil.

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