A study of the formation and branching Pattern of brachial plexus and its Variations in adult human cadavers of North karnataka

Abstract

Background and objectives - ABSTRACT The brachial plexus is highly variable in its formation and branching pattern and the knowledge of its basic anatomical pattern may be insufficient for the surgeon operating on or around these nerves and for the anaesthesiologist while working in this area. Commonly the brachial plexus can get injured in infants during the process of parturition and during adult life due to fall on an outstretched hand. Thus, the present study was an effort to know further, about variations of brachial plexus encountered during routine dissection classes, thus tracing the plexus in its entire course right from its formation in the cervical region to its branching pattern confined to the axilla and arm region of the upper extremity. Methods - The present descriptive study was carried out by dissection of 60 upper limbs of 30 cadavers, in the age group of 18 to 85 years, obtained during a study period of 2 years from the Department of Anatomy. The plexus was studied in its entire course commencing from the formation in cervical region, course through root of the neck and axilla, till the main terminal branches of the upper extremity. During the dissection, variations of brachial plexus pertaining to its formation from the roots, trunks, divisions and cords and the branching pattern were observed and data was collected. viii Results - Out of the 60 cadaveric upper limbs studied for the anatomical variations of the brachial plexus, 2 limbs ( 3.33% ) were pre-fixed plexuses. Fusion of adjacent trunks was detected in 2 limbs ( 3.33% ) , where middle and lower trunks were fused. Variations in branches of lateral cord was detected in 8 limbs ( 13.33% ) , in which extra lateral root of median nerve was detected in 7 limbs ( 11.67% ) and 4 limbs ( 6.67% ) had absence of musculocutaneous nerve. Among Posterior cord variations 2- thoracodorsal nerves were detected in 2 limbs ( 3.33% ) . In one limb ( 1.67% ) the posterior cord divided into two branches/roots, which later fused to form the radial nerve. In two limbs ( 3.33% ) the posterior cord was formed from joining of the posterior division of upper trunk to the common posterior division from fused middle and lower trunks. The median nerve was formed from 3 roots in 7 limbs ( 11.67% ) . In 7 limbs ( 11.67% ) communicating branch was encountered between musculocutaneous nerve and median nerve. In one limb ( 1.67% ) there was a communicating branch from radial nerve to ulnar nerve. In another case ( 1.67% ) radial nerve was formed from two roots, formed by splitting of the posterior cord, which subsequently united to form radial nerve. In one case ( 1.67% ) there was high division of radial nerve in the arm. In one case ( 1.67% ) axillary nerve, upper subscapular nerve and lower subscapular nerve originated from posterior division of upper trunk and only the radial nerve and thoracodorsal nerve originated from posterior cord. All the other branches from brachial plexus had been found to have no anatomical variations. Conclusion and Interpretation - In the present study, an attempt has been made to know the possible variations of the brachial plexus. Though the variations mentioned may not alter the normal ix functioning of the limb of the individual, but knowledge of the variations is of prime importance to be kept in mind, during anaesthetic and surgical procedures. The restricted sample size was a limitation in our study. Yet an earnest effort in the study has opened new avenues for further research.