Learning Objectives
By the end of this section, you should be able to:
- Describe the origin and anatomical course of the median nerve.
- Identify its major branches and their functions.
- List the motor and sensory distributions of the median nerve.
- Recognize the clinical features of median nerve injury at different levels.
Introduction
The median nerve is a major peripheral nerve of the upper limb. It supplies most of the flexor and pronator muscles of the forearm, several intrinsic muscles of the hand, and a large area of skin on the palmar surface of the hand.
This section reviews the anatomical course, motor and sensory functions, and clinical relevance of the median nerve.
- Roots: C6–T1 (may also receive fibres from C5)
- Motor:
- Most flexors and pronators in the anterior forearm
- Thenar muscles
- Lateral two lumbricals
- Sensory:
- Lateral palm (via palmar cutaneous branch)
- Palmar surface and fingertips of the lateral 3½ digits
Anatomical Course
Contributions from the median nerve from the lateral and medial cords of the brachial plexus.
Arm
- Originates in the axilla
- Descends laterally to the brachial artery, then crosses to its medial side
- Enters the forearm via the cubital fossa
Forearm
- Passes between the two heads of the pronator teres
- Travels between flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP)
- Gives off two major branches:
- Anterior interosseous nerve (AIN) – deep forearm muscles
- Palmar cutaneous branch – skin of the lateral palm
Hand
The median nerve enters the hand through the carpal tunnel, where it divides into:
-
- Recurrent branch → thenar muscles
- Palmar digital nerves → lateral 3½ digits + lateral two lumbricals
Motor Functions
Forearm
Direct branches:
- Pronator teres
- Flexor carpi radialis
- Palmaris longus
- Flexor digitorum superficialis
Via anterior interosseous nerve:
- Flexor pollicis longus
- Pronator quadratus
- The lateral half of the flexor digitorum profundus
Main actions:
- Pronation of the forearm
- Flexion of the wrist
- Flexion of fingers
Hand
- Thenar muscles (via recurrent branch)
- Lateral two lumbricals
Sensory Functions
- Palmar cutaneous branch: lateral palm (spared in carpal tunnel)
- Palmar digital branches: palmar surface and fingertips of lateral 3½ digits
Clinical Relevance
Carpal Tunnel Syndrome
Compression of the median nerve within the carpal tunnel.
Symptoms:
- Numbness, tingling, and pain in the lateral 3½ fingers
- Thenar muscle wasting in chronic cases
- Palm usually spared
Tests:
- Tinel’s sign
- Phalen’s test
Median Nerve Injury
At the Elbow (e.g., supracondylar fracture)
- Loss of forearm flexion and pronation
- Thenar muscle atrophy
- Loss of thumb flexion
- Hand of Benediction on making a fist
At the Wrist (e.g., laceration)
- Loss of thenar function
- Impaired thumb opposition
- Sensory loss in the lateral 3½ digits
- Forearm muscles remain intact
