Anatomical Variations of the Brachial Plexus Terminal Branches in Ethiopian Cadavers
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ORIGINAL COMMUNICATION Anatomy Journal of Africa. 2017. Vol 6 (1): 896 – 905. ANATOMICAL VARIATIONS OF THE BRACHIAL PLEXUS TERMINAL BRANCHES IN ETHIOPIAN CADAVERS Edengenet Guday Demis*, Asegedeche Bekele* Corresponding Author: Edengenet Guday Demis, 196, University of Gondar, Gondar, Ethiopia. Email: [email protected] ABSTRACT Anatomical variations are clinically significant, but many are inadequately described or quantified. Variations in anatomy of the brachial plexus are important to surgeons and anesthesiologists performing surgical procedures in the neck, axilla and upper limb regions. It is also important for radiologists who interpret plain and computerized imaging and anatomists to teach anatomy. This study aimed to describe the anatomical variations of the terminal branches of brachial plexus on 20 Ethiopian cadavers. The cadavers were examined bilaterally for the terminal branches of brachial plexus. From the 40 sides studied for the terminal branches of the brachial plexus; 28 sides were found without variation, 10 sides were found with median nerve variation, 2 sides were found with musculocutaneous nerve variation and 2 sides were found with axillary nerve variation. We conclude that variation in the median nerve was more common than variations in other terminal branches. Key words: INTRODUCTION The brachial plexus is usually formed by the may occur (Moore and Dalley, 1992, Standring fusion of the anterior primary rami of the C5-8 et al., 2005). and T1 spinal nerves. It supplies the muscles of the back and the upper limb. The C5 and C6 fuse Most nerves in the upper limb arise from the to form the upper trunk, the C7 continues as the brachial plexus; it begins in the neck and extends middle trunk and the C8 and T1 join to form the into the axilla. Almost all branches of the brachial lower trunk. Each trunk divides into anterior and plexus supplying the upper limb arise in the axilla posterior divisions. The anterior divisions of the (after the plexus has crossed the 1st rib) (Moore upper and middle trunks form the lateral cord; and Dalley, 1992). the anterior division of the lower trunk continues The brachial plexus is divided into as the medial cord and the posterior divisions of supraclavicular and infraclavicular parts by the all three forms the posterior cord. The cords then clavicle. Four branches of the supraclavicular give rise to various branches that form the part of the plexus arise from the roots and trunks peripheral nerves of the upper limb. Anterior of the brachial plexus namely dorsal scapular divisions of the trunks supply anterior (flexor) nerve, long thoracic nerve, nerve to subclavius compartments of the upper limb, and posterior and suprascapular nerve and are approachable divisions of the trunks supply posterior through the neck. In addition, officially unnamed (extensor) compartments. Since the brachial muscular branches arise from all five roots of the plexus is a complex structure, variations in plexus, which supply the scaleni and longus colli formation of roots, trunks, divisions and cords muscles. Submitted 27th May 2016, revised on 14th December 2016. Published online 30th January 2017. To cite: Edengenet GD, Bekele A. 2017. Anatomical Variations of the brachial plexus terminal branches in Ethiopian Cadavers. Anatomy Journal of Africa. 6: 896 - 905. www.anatomyafrica.org 896 Anatomy Journal of Africa. 2017. Vol 6 (1): 896 – 905. Branches of the infraclavicular part of the plexus Anatomical variations have clinical significance to arise from the cords of the brachial plexus and surgeons and radiologists who interpret plain are approachable through the axilla. Counting and computerized imaging and to those side and terminal branches, three branches arise anesthesiologists who place needles to from the lateral cord namely lateral pectoral administer anesthetic blocks. The awareness of nerve, musculocutaneous nerve ( terminal these variations is of interest to the surgeons, branch) and lateral root of median nerve neurologists and radiologist (Harry et al., 1997). (terminal branch), five branches arise from the So, a thorough understanding of the medial cord namely medial root of median nerve neuroanatomy of the brachial plexus, with an (terminal branch), medial pectoral nerve, medial appreciation of the possible anatomic variations cutaneous nerve of the arm, median cutaneous that may occur is necessary for effective clinical nerve of the forearm and ulnar nerve (terminal practice. Anatomical Variations may occur in the branch) and five branches arise from the origin and/or combination of branches and in the posterior cord namely upper subscapular nerve, relationship to the axillary artery and scalene lower subscapular nerve, thoracodorsal nerve, muscles (Moore and Dalley, 1992, Loukas et al., axillary nerve(terminal branch) and radial nerve 2008, Johnson et al., 2010) (terminal branch) (Moore and Dalley, 1992, Drake et al., 2014). Anatomical variation of the brachial plexus is clinically important as this knowledge may help The topography of the brachial plexus and its the anesthesiologists and the surgeons to avoid anatomical variation play an essential role in any inadvertent damage to nerves and blood diagnoses, therapy and surgical procedures vessels during blocks and surgical interventions. (Loukas et al., 2008, Johnson et al., 2010).This Knowledge of anatomical variations in brachial variation may lead to deviation from the plexus branching pattern is also important to expected dermatome distribution as well as radiologists who interpret plain and differences in the motor innervation of muscles computerized imaging and anatomists who teach of the upper limb. Such variations may anatomy for medical and paramedical students. predispose patients to certain pathology such as The aim of this research was an assessment of thoracic outlet syndrome and may alter surgical anatomical variation of the brachial plexus approaches to the brachial plexus (Pellerin et al., terminal branches on 20 Ethiopian cadavers in 2010). Variation in brachial plexus formation and selected medical schools in Ethiopia. branching pattern has clinical implications as it may result in failure of regional brachial or axillary block (Moore and Dalley, 1992). MATERIALS AND METHODS Observational based descriptive study design by using formalin, alcohol, glycerin and phenol was conducted to assess anatomical variation of for routine dissection sessions and the materials the brachial plexus terminal branches on 20 necessary to collect data were blade, forceps, Ethiopian cadavers. Purposive sampling gloves, camera and a check list. technique was used for selecting 20 cadavers Data collection procedure was by using the from the available limited number of cadavers dissection manual Cunningham (Cunningham, obtained from Gondar, Bahir Dar, Hawasa, Addis 1903). The brachial plexus was exposed in the Ababa universities, Hayat Medical College and left and right of 20 cadavers and the anatomy of St. Paul Hospital Millennium Medical College brachial plexus (terminal branches) and its Departments of Human Anatomy. They were relationship with muscles and blood vessels embalmed according to conventional methods around were inspected in the axilla and upper www.anatomyafrica.org 897 Anatomy Journal of Africa. 2017. Vol 6 (1): 896 – 905. limb. All of the dissections were photographed between the artery and vein, while the radial and recorded. nerve lies behind the artery. The radial nerve was traced upwards and at the lower border of To expose terminal branches of the brachial subscapularis and the axillary nerve identified plexus skin incisions were made along the middle passing backwards with the posterior humeral of the sternum vertically, extending the incision circumflex artery. The medial, lateral and along the clavicle horizontally to its acromial end posterior cords of the brachial plexus which are and another incision from the sternum to the found around the axillary artery were exposed. axilla. The flaps of skin and superficial fascia were reflected laterally by blunt dissection, and To ensure quality of data, after dissection, the deep fascia in the deltopectoral groove divided. dissected specimen was photographed and The fascia from the anterior part of pectoralis clarity was checked by the advisor. The quality major and deltoid were removed and the checking was done at the end of each dissection clavicular head of pectoralis major cut across and cross-checking was done before analysis. below the clavicle and reflected towards its insertion. The remainder of the pectoralis major Thematic approach was applied to compile and was cut about 5cm from the sternum and its analyze findings on anatomical variations of parts reflected medially and laterally. The brachial plexus formation and terminal branches. clavipectoral fascia was removed from pectoralis minor to expose the vessels and nerves in the Ethical clearance was obtained from school of axilla. Loose connective tissue, fat and lymph medicine ethical review committee of University nodes were removed from the axilla to expose of Gondar. Study subjects are prepared for its contents. The coracobrachialis and short head teaching purposes in the departments of human of biceps muscles was exposed and the median anatomy. An official letter was submitted to nerve and axillary artery medial to these muscles Bahir Dar University, Hawasa University, Addis identified, together with musculocutaneous Ababa University, Hayat Medical College and St. nerve entering the deep surface