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Home , Brachialis muscle, Coracobrachialis muscle

International Journal of Health Sciences and Research www.ijhsr.org ISSN: 2249-9571

Case Report

An Entrapment of Median and Brachial Due to Double Muscular Variation in the

Sharadkumar Pralhad Sawant**@, Shaguphta T. Shaikh*, Rakhi M. More*

**Associate Professor, *Assistant Professor, Department of Anatomy, K. J. Somaiya Medical College, Somaiya Ayurvihar, Eastern Express Highway, Sion, Mumbai-400 022.

@Correspondence Email: [email protected]

Received: 09/08//2012 Revised: 07/09/2012 Accepted: 07/09/2012

ABSTRACT

During routine dissection for First MBBS students on a 65 years donated embalmed male cadaver in the Department of Anatomy, K.J.Somaiya Medical College, we observed that the and the passed through the in the right arm. The superficial fibres of the coracobrachialis muscle were normal in their insertion i.e. on the middle 5 cm of the medial border of the shaft of the . We also encountered an accessory slip of the originated from anteromedial surface of the shaft of humerus and got inserted into the medial epicondyle of the humerus. The accessory slip of the brachialis muscle passed over the brachial artery and the median nerve. This may result in neurovascular compression and it may have some mechanical advantages and disadvantages during the movement of joint. The knowledge of such variations were important for medical fraternity such as surgeons, orthopaedicians, neurologists, radiologists and physiotherapist for dealing with injuries or operations around the elbow joint. Key words: Coracobrachialis Muscle, Brachialis Muscle, Accessory Belly, Median Nerve, Brachial Artery, Variation, Neurovascular Compression, Injuries, Elbow Joint.

INTRODUCTION short head of . The tendon is The coracobrachialis muscle shows continued into a muscular belly of varying several interesting morphological and development which is inserted into the anatomical characteristics. It is the medial border of the humerus. The lower counterpart in the arm of the adductors extent of the insertion is marked by the (longus, brevis, magnus) of the thigh. It nutrient foramen of the humerus, for the arises from the apex of the , nutrient branch of the brachial artery runs where it is fused with the medial side of the along the lower border of the muscle. The

International Journal of Health Sciences & Research (www.ijhsr.org) 107 Vol.2; Issue: 6; September 2012 upward extent of the insertion cannot be supplies its lateral part. The brachialis seen on most bones, the muscle usually muscle is a flexor of the elbow joint. The leaves no impression. The brachialis muscle along with the supinator passes through the muscle forms the floor of the . muscle and supplies it. Compared to the The content of cubital fossa from medial to morphological interest of this muscle its lateral side are median nerve, brachial action is negligible. It is a weak adductor of artery, tendon of biceps brachii muscle and the joint, the main adductors of . All these contents of cubital which are pectoralis major and latissimus fossa are present anterior to the brachialis dorsi. (1, 2) muscle. The brachialis muscle may be In some animals the coracobrachialis derived into two or more parts. It may be muscle has three heads; (3) in man two have fused with the , the pronator fused, trapping the nerve between them, and teres or the biceps brachii muscle. the third part has become suppressed. The Sometimes the brachialis muscle may give occasional supratrochlear spur (on the slip to or . The anteromedial aspect of the lower humerus) blood supply of the brachialis muscle is may be continuous with a ligament (of derived from the superior and inferior Struthers) which passes to the medial branches. The superior branch is from the epicondyle and represents the remains of the brachial artery and the inferior branch is third head. (4) The median nerve or brachial either from the superior ulnar collateral artery or both may run beneath it and be artery or from the brachial artery. The subjected to compression. accessory supplying the brachialis The brachialis is the muscle of the muscle are small and variable in number. front of the arm region. It is situated behind They may arise from the brachial artery, the biceps brachii muscle. The brachialis superior and inferior ulnar collateral arteries arises from the lower half of the front of the or the profunda brachii artery. The brachialis shaft of the humeres including both the muscle can be tested clinically by palpating anteromedial and anterolateral surface of the its fibres during flexion of elbow joint shaft of the humerus. It also take origin from against resistance. lower part of the present on the posterior surface of the shaft of the humerus and the CASE REPORT medial intermuscular septum attached to the During routine dissection for First medial border of the shaft of the humerus. It MBBS students on a 65 years donated is separated distally from the lateral embalmed male cadaver in the Department intermuscular septum by brachioradialis and of Anatomy, K.J.Somaiya Medical College, extensor carpi radialis longus muscle. The the variations were found in the right upper brachialis covers the anterior part of the limb. It was unilateral. The median nerve elbow joint. The fibres of brachialis muscle and the brachial artery passes through the converge to form a thick and broad tendon coracobrachialis muscle. The superficial which is inserted into the ulnar tuberosity fibres of the coracobrachialis muscle were and to a rough surface on the anterior part of normal in their insertion i.e. on the middle 5 the coronoid process of . The brachialis cm of the medial border of the shaft of the muscle is hybrid muscle, it has dual nerve humerus. An accessory slip of brachialis supply. C5,6 fibres of the musculocutaneous muscle originated from the anteromedial nerve supplies the medial part of the muscle surface of the shaft of the humerus and got where as C7 fibres of the radial nerve inserted into medial epicondyle of the International Journal of Health Sciences & Research (www.ijhsr.org) 108 Vol.2; Issue: 6; September 2012 humerus. This accessory slip of the rare and not documented in the literature. brachialis muscle passed over the brachial The further course of the brachial artery and artery and the median nerve. The median the median nerve was normal. The accessory nerve and the brachial artery passes deep to slip of the brachialis muscle was supplied by the superficial fibres of the coracobrachialis the musculocutaneous nerve. The left arm of muscle in the upper 1/3rd of the arm and the same cadaver was normal. The deep to the accessory slip of brachialis photographs of the variations were taken for muscle in the lower 1/3rd of the arm. Such proper documentation and for ready type of double muscular variation is very reference.

Figure 1: Photographic representation of the superficial fibres of the coracobrachialis muscle and an accessory slip of the brachialis muscle passed over the brachial artery and the median nerve.

Figure 2: Photographic representation of the superficial fibres of the coracobrachialis muscle passed over the brachial artery and the median nerve.

International Journal of Health Sciences & Research (www.ijhsr.org) 109 Vol.2; Issue: 6; September 2012

Figure 3: Photographic representation of an accessory slip of the brachialis muscle passed over the brachial artery and the median nerve.

DISCUSSION formed by fusion of the muscle primordia The accessory head of within the different layers of the arm at coracobrachialis muscle may be attached to certain stages of development; thereafter, the , medial epicondyle or the some muscle primordia disappears through medial intermusculur septum. (2) The clinical cell death. The morphological variations of implication of the accessory head of the the coracobrachialis muscle may be due to coracobrachialis is that it has the potential to failure of muscle primordia to disappear cause the median nerve entrapment and the during the embryological development. (9) brachial artery compression. Various studies The presence of accessory belly of have described the compression of the the brachialis muscle have been reported by median nerve and the brachial artery with many authors. Dharap observed an unusual anomalous muscles. (5, 6, 7, 8) In the present muscle that passed obliquely from the case the accessory head of the middle of the humerus anterior to the coracobrachialis muscle arises from median nerve and brachial artery, forming a superficial fibres of the coracobrachialis tunnel for them, before inserting with the muscle having 3cm muscle belly and 15cm common origin of the flexor tendinous band. It extended downwards and muscles. (5) Loukas et al. reported an medially in front of the median nerve and accessory brachialis muscle originating from brachial artery and finally got inserted on middle of the shaft of the humerus and the the anteromedial aspect of the medial medial intermuscular septum. The accessory epicondyle of the humerus. The accessory brachialis muscle crossed over both the head of the coracobrachialis muscle reported brachial artery and the median nerve. The in this case may be explained on the basis of distal tendon split to surround the median the embryogenesis of the muscles of the nerve before inserting into the brachialis arm. During development, the limb bud tendon and the common tendon of the mesenchyme of the lateral plate antebrachial flexor compartment muscles. differentiates into the intrinsic muscles of (10) Paraskevas et al. have described a variant the upper limb. A single muscle mass is muscle on the left side arising from the International Journal of Health Sciences & Research (www.ijhsr.org) 110 Vol.2; Issue: 6; September 2012 medial border of the brachialis muscle and nerve and brachial artery by various types of after bridging the median nerve, the brachial structures leading to clinical artery and vein; it was fused with the medial neurovasculopathy has been reported. (17, 18) intermuscular septum. The muscle was On contraction, these muscles can compress innervated by the musculocutaneous nerve. the median and ulnar , leading to (11) George and Nayak have described few further irritation of the nerves. Also, on fleshy fibers of brachialis arising from the contraction these muscles can compress both distal third of the muscle and merging with the brachial artery and brachial veins. The superficial flexors of the forearm and to the possibility of those muscles anomalies medial aspect of the olecranon process of should, therefore, be considered when in any ulna. (12) Rajanigandha et al. reported the patient, a high median or ulnar or medial occurrence of an accessory brachialis antebrachial cutaneous nerve paralysis exists muscle that formed a fibro-muscular tunnel with symptoms of lower brachial artery or after blending with the medial intermuscular brachial vein compression. Also, these septum. (13) An anomalous muscle, without muscles should not be mistaken for tumors any contribution from the biceps or the on MR imaging of the arm. (19) The fibres of brachialis, originated between the accessory slip of the brachialis muscle can coracobrachialis and the brachialis from the be used in reconstruction surgery of the humerus, has been reported previously. This annular ligament and the medial collateral muscle passed obliquely across the front of ligament of elbow joint. the brachial artery and the median nerve. The muscle also was found to blend with Developmental basis: common origin of flexor muscles. There are Embryologically, the intrinsic three well described entrapment syndromes muscles of the upper limb differentiate in involving the median nerve or its branches, situ, opposite the lower six cervical and namely carpal tunnel syndrome, pronator upper two thoracic segments, from the limb teres syndrome and anterior interosseous bud mesenchyme of the lateral plate syndrome. A few case reports were found in mesoderm. The formation of muscular the literature, explaining the possible median elements in the limbs takes place shortly nerve entrapment due to a third head of after the skeletal elements begin to take biceps brachi. (14, 15) Even though anatomy shape. At a certain stage of development, the literature hardly mentions the median nerve muscle primordia within the different layers compression due to bicipital aponeurosis, a of the arm fuse to form a single muscle fewresearch reports say that it could be a mass. (20) Langman stated, however, that cause of high median nerve compression, some muscle primodia disappear through along with brachial artery. (16) The cell death despite the fact that cells within simultaneous occurrence of the above them have differentiated to the point of mentioned variants in the same specimen containing myofilaments. (21) Failure of has not been reported to the best of our muscle primordia to disappear during knowledge. Although causes no symptoms embryologic development may account for most of the time, such structures have the the presence of the accessory muscular potential to compress the median nerve with bands reported in this case. consequent functional impairment. Such accessory muscle slips may also compress CONCLUSION the underlying arteries viz., in The existence of such double the present case. Compression of the median variations should be kept in mind by the International Journal of Health Sciences & Research (www.ijhsr.org) 111 Vol.2; Issue: 6; September 2012 surgeons operating on patients with high median nerve palsy and brachial artery REFERENCES compression, by the orthopaedicians dealing 1. Standring S, ed. Gray’s Anatomy, with fracture of the humerus, the The anatomical basis of clinical radiologists while doing radiodiagnostic practice. 39th Ed., Elsevier Churchill procedures e.g.CT scan, MRI of the arm and Livingstone. 2005; 855, 859. angiographic studies and also by the 2. 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International Journal of Health Sciences & Research (www.ijhsr.org) 113 Vol.2; Issue: 6; September 2012