A Study of Median Nerve and Its Variations: Formation, Course and Distribution

BACKGROUND: Median Nerve is formed in the axilla by the union of medial and lateral roots. Pronator syndrome is entrapment of the median nerve between the two heads of the pronator teres muscle. Entrapment of the median nerve in the carpal tunnel is one of the most common entrapment neuropathy syndromes in clinical practice. OBJECTIVES: 1. To study the variations in the formation of median nerve and its course. 2. To study the morphometry of median nerve branches innervating pronator teres. 3. To study the relation of median nerve and pronator teres. 4. To study the branching pattern of median nerve in hand. MATERIALS: 50 embalmed adult human cadavers from the Institute of Anatomy, Madras Medical College,Chennai-03. Parameters were measured using digital Vernier calipers. RESULTS: In 12% of specimens, median nerve found to have trifurcate origin. Median nerve was formed anterior and posterior to axillary artery in 4% and 2% respectively. Musculocutaneous nerve was absent in 14% of specimens. One branch of median nerve to pronator teres was seen in 72% of specimens. Among this, in 56% of specimens, it takes origin above the level of intercondylar line. And in 8% and 36% of specimens, it takes origin at and below the level of intercondylar line. The average length of these branches was 3.8cms median nerve passing between humeral and ulnar heads of pronator teres muscle was observed in 82% of specimens, passing through and below the ulnar head of pronator teres in 6% and 2% specimens respectively. It was passing deep to the humeral head, when ulnar head of pronator teres was absent in 5 specimens (10%). Persistent median artery was seen in 6% specimens. It was divided into terminal branches medial and lateral above the level of flexor retinaculum in 4% of specimens. All median nerve studied were given off 5 digital branches which supply lateral three and half fingers.