Relations of Median Nerve
The relations of the median nerve change progressively as it descends from the axilla to the palm, mostly in relation to the brachial artery and, distally, the flexor tendons of the forearm.
In the Axilla
- The median nerve is formed by its lateral and medial roots, which embrace the third part of the axillary artery and unite on its lateral or anterior aspect.
In the Arm
- In the upper part of the arm, the median nerve lies lateral to the brachial artery.
- At the level of insertion of coracobrachialis (mid-arm), it crosses the brachial artery (usually anteriorly) to come to lie on its medial side.
- It continues distally medial to the brachial artery up to the cubital fossa.
In the Cubital Fossa
- Lies medial to the brachial artery.
- Lies behind the bicipital aponeurosis.
- Lies in front of brachialis.
- The brachial artery here divides into radial and ulnar arteries; the median nerve remains medial to this bifurcation.
At the Elbow / Entry into Forearm
- The median nerve leaves the cubital fossa by passing between the two heads of pronator teres (superficial humeral head and deep ulnar head).
- Here it crosses in front of the ulnar artery, separated from it by the deep (ulnar) head of pronator teres.
In the Forearm
- Passes deep to the fibrous arch of flexor digitorum superficialis (FDS).
- Runs down on the posterior surface of FDS, lying on flexor digitorum profundus (FDP).
- Accompanied by the median artery (a branch of the anterior interosseous artery).
- About 5 cm above the flexor retinaculum, it emerges from behind the lateral border of FDS to become superficial.
Near the Wrist
- Lies between the tendons of flexor carpi radialis (laterally) and flexor digitorum superficialis (medially).
- Overlapped by the tendon of palmaris longus.
In the Carpal Tunnel / Palm
- Enters the palm deep to the flexor retinaculum, through the carpal tunnel.
- Lies in the narrow space of the carpal tunnel in front of the ulnar bursa (which encloses the long flexor tendons).
- Immediately distal to the retinaculum, it divides into lateral and medial divisions.
Summary Table
| Region | Key Relation |
|---|---|
| Axilla | Embraces axillary artery (formation) |
| Upper arm | Lateral to brachial artery |
| Mid-arm | Crosses brachial artery anteriorly → medial side |
| Cubital fossa | Medial to brachial artery; behind bicipital aponeurosis; in front of brachialis |
| Elbow/forearm entry | Between two heads of pronator teres; crosses anterior to ulnar artery |
| Forearm | Deep to FDS, on FDP, with median artery |
| Lower forearm | Between FCR and FDS tendons, under palmaris longus |
| Carpal tunnel | Deep to flexor retinaculum, anterior to ulnar bursa |