Median nerve: course, branches, distribution and lesions

Median nerve: terminal branch of the brachial plexus, root value C5 to T1, supplying most forearm flexors and the lateral palm.

Origin and Course

Formed in the axilla by union of the lateral root (C5, C6, C7) and medial root (C8, T1) of the brachial plexus.
Axilla → arm (crosses to medial at midhumerus) → cubital fossa (exits between pronator teres heads) → forearm (deep to FDS) → carpal tunnel → palm, terminal division.
In the axilla lies lateral to the axillary artery; enters the arm at the lower border of teres major.
In the arm, lies lateral to the brachial artery then crosses to its medial side at midhumerus (coracobrachialis insertion level).
In the cubital fossa, lies medial to the brachial artery and biceps tendon, covered by the bicipital aponeurosis.
Leaves the cubital fossa between the two heads of pronator teres, giving off the anterior interosseous nerve at this point.
In the forearm runs deep to flexor digitorum superficialis, becoming superficial about 5 cm proximal to the flexor retinaculum.
Enters the palm through the carpal tunnel, deep to the retinaculum.
The medial root crosses in front of the third part of the axillary artery to join the lateral root in a Y shape, in front of or lateral to the artery.
The bicipital aponeurosis separates the nerve from the median cubital vein in the cubital fossa; in the forearm it passes behind the tendinous arch between the two heads of FDS.
In the carpal tunnel it lies superficial to the tendons of FDS, FDP and FPL and their synovial bursae, flattening and dividing into its terminal divisions at the retinaculum's distal border.