A study of neuroanatomical variations of median nerve in human cadavers

Abstract

Background and objectives ABSTRACT Median nerve is called labourers’ nerve. Comprehensive knowledge pertaining to its anatomical variations is extremely important in clinical and surgical procedures so as to avoid injury to it. The objectives of the study were to know about the variations of median nerve in its formation course, branching pattern and termination. Methods Dissection method was employed and 50 upper limbs were studied for anatomical variations of median nerve obtained from the department of Anatomy. Results The median nerve was found to be formed by two roots in 37( 74% ) and by three roots in 13 ( 26% ) specimens. It was found to be formed in axilla in 32 ( 64% ) , in the upper third of arm in 10 ( 20% ) , middle third of arm in 6 ( 12% ) and lower third of arm in 2 ( 4% ) specimens. The median nerve coursed lateral to brachial artery in 47 ( 94% ) and medial to brachial artery in 3 ( 6% ) specimens. In one specimen high division of brachial artery in the middle third of the arm was observed along with formation of median nerve at the same level. Formation of median nerve was lateral to axillary artery in 42 ( 84% ) specimens, anterior to axillary artery in 5 ( 10% ) specimens, medial to axillary artery in 3 ( 6% ) specimens. Absence of musculocutaneous nerve was noted in 6 ( 12% ) specimens and it was bilateral in one cadaver. In two out of these six specimens where absence of musculocutaneous nerve was noted, there were concomitant variations in the formation of median nerve as vii well. In both of these specimens the median nerve was formed by three roots. In one specimen there was extremely thin normal lateral root and abnormally very thick second lateral root of median nerve. In another specimen apart from three roots there was vascular variation as well. Vena comitans was coursing within the loop formed by the two lateral roots of the median nerve. The median nerve passed between two heads of pronator teres in 44 ( 88% ) specimens, deep to the muscle in 2 ( 4% ) , through ulnar head in 2 ( 4 % ) and the nerve passed deep to humeral head the ulnar head being absent in 2 ( 4% ) specimens. The median nerve passed deep to flexor digitorum superficialis in 48 ( 96% ) and piercing the muscle in 2 ( 4% ) specimens. The median nerve becoming superficial in middle third of the forearm was noted in 10 ( 20% ) specimens. Palmaris longus was absent in 2 ( 4% ) specimens. Communications between median nerve and musculocutaneous nerve were observed in 6 ( 12% ) specimens. In one specimen along with communication between median and musculocutaneous nerve in middle third of arm there was a concomitant arterial variation as well. In that specimen high division of axillary artery was observed. Communications between median and ulnar nerve in forearm and hand were seen in 4 ( 8% ) each. The median nerve was found to terminate in the palm into 3-5 branches in 5 ( 10% ) specimens. Conclusion and interpretation We are optimistic that the data obtained in our study would be helpful for the clinicians. It is probable that the differences observed as compared to other studies may be due to differences in the sample size. viii The present study concludes that, the different types of variations in cadavers which have been studied would be of immense help for successful clinical and surgical procedures. The present study may provide additional information as such neurovascular variations encountered here are important to be noted during surgical procedures as these are more prone to iatrogenic injuries.