Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Available Online at http://www.recentscientific.com International Journal of Recent Scientific Research Vol. 5, Issue, 1, pp.05-07, January, 2014 International Journal of Recent Scientific Research ISSN: 0976-3031 RESEARCH ARTICLE UNUSUAL BILATERAL PRESENCE OF THIRD HEAD OF STERNOCLEIDOMASTOID MUSCLE AND ITS CLINICAL SIGNIFICANCE - A CASE REPORT Pushpa, MS and Nandhini, V Department of Anatomy, Bangalore Medical College and Research Institute, Fort, Bangalore, India- 560002 ARTICLE INFO ABSTRACT Article History: The Sternocleidomastoid is a paired muscle o0f the neck which flexes and rotates the head. It also serves as an accessory muscle of inspiration, along with the scalene muscles (Hasan, 2011). An accessory head of Sternocleidomastoid muscle was encountered bilaterally during routine dissection of the head and neck region in a female cadaver around 60 years old. Embryological basis for the supernumerary clavicular head may be the unusual separation or division of mesoderm at the sixth branchial arch (Mehta V et al., 2012, Rani et al., 2011). The Sternocleidomastoid muscle stays as an important landmark for anatomists, dental surgeons, oncologists, orthopaedicians, neurosurgeons, plastic surgeons and anaesthetists in many surgical procedures, knowledge of such variations will prevent major complications during interventions in this region. Received 12th, December, 2013 Received in revised form 22th, December, 2013 Accepted 11th, January, 2014 Published online 28th, January, 2014 Key words: Sternocleidomastoid, accessory head, bilateral variation © Copy Right, IJRSR, 2014, Academic Journals. All rights reserved. INTRODUCTION Sternocleidomastoid is present in the cervical region, descends obliquely across the side of the neck and serves as an important landmark in dividing into anterior and posterior triangles (Mehta et al., 2012). It is thick and narrow centrally, and broader and thinner at each end. The muscle is attached inferiorly by two heads. The medial or sternal head is rounded and tendinous, arises from the upper part of the anterior surface of the manubrium sterni and ascends posterolaterally. The lateral or clavicular head, which is variable in width and contains muscular and fibrous elements, ascends almost vertically from the superior surface of the medial third of the clavicle. The two heads are separated near their attachments by a triangular interval which corresponds to a surface depression, the lesser supraclavicular fossa. As they ascend, the clavicular head spirals behind the sternal head and blends with its deep surface below the middle of the neck, forming a thick, rounded belly. Sternocleidomastoid inserts superiorly by a strong tendon into the lateral surface of the mastoid process from its apex to its superior border, and by a thin aponeurosis into the lateral half of the superior nuchal line. The clavicular fibres are directed mainly to the mastoid process; the sternal fibres are more oblique and superficial, and extend to the occiput. The direction of pull of the two heads is therefore different, and the muscle may be classed as 'cruciate' and slightly 'spiralized'. The muscle is innervated by the spinal part of accessory nerve along with branches from ventral rami of C2-3 and sometimes ventral rami of C4 spinal nerves. It is vascularized by the branches of suprascapular, superior thyroid, occipital and posterior auricular arteries. Acting alone, the Sternocleidomastoid muscle flexes the neck laterally and rotates the face to the opposite side. Acting together, the muscle of two sides flexes the head and neck forcibly (Williams et al., 1995). A wide mention of supernumerary and accessory musculature has been made in the anatomic, surgical, and radiology literatures. In majority of cases, accessory muscles are asymptomatic and usually incidental findings at surgery or imaging. However, sometimes accessory muscles may produce clinical symptoms. These symptoms may be related to a palpable swelling or compressive effect on neurovascular structures (Sookur et al., 2008). MATERIALS AND METHODS During the routine cadaveric dissection for undergraduate teaching in the Department of Anatomy, Bangalore Medical College and Research Institute, Bangalore the presence of third head or accessory head of Sternocleidomastoid was observed bilaterally in a female cadaver around 60 years of age. Case Report Right Sternocleidomastoid - It had three heads. 1st head / sternal head had a rounded origin from anterior surface of the manubrium sterni being 1.2 cms wide, got inserted to the mastoid process and superior nuchal line of occipital bone with 3 cms width. 2nd head / clavicular head originated from superior surface of medial one third of clavicle, 2.5cms from the sternal end of clavicle measuring about 1.4 cms in breadth. Before insertion it merged with deeper surface of the sternal head at a distance of 4 cms from clavicle and got attached to the mastoid and occiput deep to the sternal head. 3rd head / accessory clavicular head which had its origin from superior surface of clavicle, 4.5 cms from the sternal end of clavicle about 0.5 cm wide, it merged with sternal head above the * Corresponding author: Pushpa, MS Department of Anatomy, Bangalore Medical College and Research Institute, Fort, Bangalore, India- 560002 International Journal of Recent Scientific Research, Vol. 5, Issue, 1, pp.05-07, January, 2014 clavicular head at a distance of 4 cms from the clavicle, then it got attached to the superior nuchal line for insertion corresponding to the fibres of sternal head. At the fusion of the clavicular heads with the sternal head it was 2.5 cms wide. attached to the superior nuchal line for insertion corresponding to the fibres of sternal head. At the fusion of the clavicular heads with the sternal head it was 2.6 cms wide. Medial lesser supraclavicular fossa - the depression was between 1st and 2nd heads, base about 1.5 cm and height of about 4.6 cms on either side. Internal jugular vein was found in the triangle. Lateral / additional lesser supraclavicular fossa - the depression was between 2nd and 3rd heads, base about 0.7 cm and height of about 5.3 cms on either side. Spinal accessory nerve was found between 1st and 3rd heads on the superficial aspect and 2nd head on the deeper aspect and supplied the three heads. Fig 1 Bilateral presence of third head of SCM (SCM – Sternocleidomastoid) Medial lesser supraclavicular fossa - the depression was between 1st and 2nd heads, base about 0.8 cm and height of about 3.2 cms on either side. Internal jugular vein was found behind the second head. Lateral / additional lesser supraclavicular fossa - the depression was between 2nd and 3rd heads, base about 0.6 cm and height of about 3.6 cms on either side. Spinal accessory nerve was found between 1st and 3rd heads present superficially and 2nd head on its deeper aspect and supplied the three heads. Fig 3 Spinal accessory nerve DISCUSSION Variations in the Sternocleidomastoid are seen usually at its origin, found rare at its insertion. It may cause different clinical conditions limiting the function of neck. The Sternocleidomastoid may consist of five parts in two layers (superficial and deep layers), out of these five parts the superficial layer consists of superficial sternomastoid, sterno-occipital, and cleido-occipital parts. Deep layer have sternomastoid and cleidomastoid parts. Comparative studies in mammals have demonstrated that the Sternocleidomastoid muscle frequently separated into above five parts which are arranged in two layers. The fusion of these two muscles is considered to be a normal feature (Bergman et al., 1988). In a study, bipartite clavicular attachment of the Sternocleidomastoid in the neck of an adult male cadaver was reported. It was observed unilaterally on the left side of the neck, where the clavicular head of the muscle exhibited two bellies, one medial and one lateral. While the medial belly was fused with the sternal head, the lateral belly appeared to blend with the medial. Cranially, the Sternocleidomastoid attached to the mastoid process and superior nuchal line. (Mehta V et al., 2012). The accessory muscle can be confused with soft tissue masses such as lymphadenopathies and venous thromboses during physical examination (Fazliogullari Z et al., 2010). Left Sternocleidomastoid – It had three heads. 1st / sternal head origin was rounded from the anterior surface of the manubrium sterni measuring about 0.6 cm in width, inserted to the mastoid process and superior nuchal line of occipital bone at a breadth of 3 cms. Fig 2 Left SCM with the supraclavicular fossas. (IJV – Internal Jugular Vein, MSCF – Medial Supraclavicular Fossa, LSCF – Lateral Supraclavicular Fossa) In another study the additional third head originated from the middle third of the clavicle and joined the normal two heads (sternal and clavicular) of the muscle in the middle of the neck. The insertion and nerve supply of the muscle was normal. The additional head covered the major neurovascular structures in the subclavian triangle (Cherian SB & Nayak S, 2008). Additional slip of clavicular head was observed bilaterally creating one more surface depression, the additional lesser supraclavicular fossa. The additional slip was also supplied by a branch from the spinal part of the accessory nerve (Rao et al., 2007). The surgeons should be aware of the presence of such additional slips while performing 2nd head / clavicular head originated from superior surface of medial one third of clavicle, 3.7 cms from the sternal end of clavicle measuring about 0.5 cm in width. Before insertion it merged with deeper surface of the sternal head at a distance of 7 cms from clavicle and got attached to the mastoid and occiput deep to the sternal head. 3rd head / accessory clavicular head originated from superior surface of clavicle, 5 cms from the sternal end of clavicle, it was 0.9 cm wide. Before insertion it merged with sternal head above the clavicular head at about 7.5 cms from the clavicle, then it got 6 International Journal of Recent Scientific Research, Vol. 5, Issue, 1, pp.05-07, January, 2014 References surgeries in head and neck regions as these can be used as myocutaneous flaps without disturbing the normal morphology of muscle (Rani et al., 2011). 1. Hasan, T. 2011. Variations of the Sternocleidomastoid Muscle: A Literature Review. The Internet Journal of Human Anatomy. 1 (1), 2. Mehta, V.; Arora, J.; Kuma, A.; Nayar, A. K.; Ioh, H. K.; Gupta, V.; Suri, R.K.; Rath, G. 2012. Bipartite clavicular attachment of the sternocleidomastoid muscle: a case report. Anatomy and Cell Biology. 45, 66-69. 3. Rani, A.; Srivastava, A. K.; Rani, A.; Chopra, J. 2011. Third head of sternocleidomastoid muscle. International Journal of Anatomical Variations. 4, 204-206. 4. Williams, P. L.; Bannister, L. H.; Berry, M. M.; Collins, P.; Dyson, M.; Dussek, J. E.; Ferguson, M. W. J. 1995. Gray's Anatomy. 38th ed. Baltimore, Churchill Livingstone. 804-5. 5. Sookur, P. A.; Naraghi, A.M.; Bleakney, R.R.; Jalan, R.; Chan, O.; White, L.M. 2008. Accessory Muscles: Anatomy, Symptoms, and Radiologic Evaluation. Radiographics. 28, 481–499. 6. Bergman, R. A.; Thomson, S. A.; Afifi, A. K.; Saadeh, F. A. 1988. Compendium of Anatomic Variation, In: Muscles. Baltimore, Urban and Schwarzenberg. 32-33. 7. Fazliogullari, Z.; Cicekcibasi, A.E.; Dogan, N.U.; Yilmaz, M.T.; Buyukmumcu, M.; Ziylan, T. 2010. The levator claviculae muscle and unilateral third head of the sternocleidomastoid muscle: case report. International Journal of Morphology. 28, 929-932. 8. Cherian, S. B.; Nayak, S. 2008. A rare case of unilateral third head of sternocleidomastoid muscle. International Journal of Morphology. 26(1), 99-101. 9. Rao, T.R.; Vishnumaya, G.; Prakashchandra, S.K.; Suresh, R. 2007. Variation in the origin of sternocleidomastoid muscle. A case report. International Journal of Morphology. 25, 621–623. 10. Sirasanagandla, S. R.; Bhat, K. M. R.; Pamidi, N.; Somayaji, S. N. 2012. Unusual third head of the sternocleidomastoid muscle from the investing layer of cervical fascia. International Journal of Morphology. 30(3), 783-785. 11. Kumar, M.S.; Sundaram, S.M.; Fenn, A.; Nayak, S.R.; Krishnamurthy, A. 2009. Cleido-occipital platysma muscle: a rare variant of sternocleidomastoid muscle. International Journal of Anatomical Variations. 2, 9-10. Embryology During the development, Sternocleidomastoid and trapezius muscles share a common premuscle mass from the last two occipital and upper cervical myotomes. This muscle mass splits and separates at 9 mm stage of development (Sirasanagandla, S. R et al., 2012). This myotome segregates into the ventral Sternocleidomastoid and dorsal trapezius. The trapezius and Sternocleidomastoid arises from a common pre-muscle mass in the occipital region just caudal to the sixth branchial arch. Therefore, occasionally the margins of these two muscles make contact with each other. Moreover, HOX D4 and somitic mesoderm contributes to the development of these muscles where they are connected to skeletal elements only by posterior otic neural-crest derived connective tissue. Since HOX D4 and somites contribute muscle cells to branchial neck muscles, these myoblasts seem to associate with neural-crest derived muscular connective tissue (Kumar et al., 2009). Significance The Sternocleidomastoid has many vital structures lying under its cover, like the common carotid artery, accessory nerve, brachial plexus roots, cervical plexus nerves and lymph nodes (Hasan T, 2011). An accurate and appropriate anatomical knowledge for anaesthetists is mandatory before attempting a central venous catheterisation approach for internal jugular vein cannulation. The presence of an additional clavicular belly narrows the minor supraclavicular fossa of the neck, leading to cumbersome internal jugular vein cannulation. This difficulty during cannulation can accidentally puncture the neighbouring neurovascular structures thereby leading to haematoma formation or resulting in neural deficits. (Mehta V et al., 2012). CONCLUSION Presence of the abnormal muscles in the neck is not very common. In most cases, these muscles go unnoticed as they do not produce any symptoms in the individual. These abnormal muscles may cause functional deficits by compressing the neurovascular structures. Plastic surgeons, orthopaedicians and dental surgeons should be aware of these variations while taking muscle flap in reconstructive surgeries. Acknowledgements Authors are grateful to Dr. Priya Ranganath, Professor & HOD and to all staffs of department of Anatomy, BMCRI, Bangalore. ******* 7