Radial Nerve Injury

Excerpt

The radial nerve stems from the posterior cord of the brachial plexus and supplies the upper limb. It also supplies the triceps brachii muscle of the arm, the muscles in the posterior compartment of the forearm (also known as the extensors), the wrist joint capsule, and aspects of the dorsal skin of the forearm and hand. The radial nerve proper innervates:

1. Triceps

2. Anconeus

3. Extensor carpi radialis longus (ECRL)

4. Extensor carpi radialis brevis (ECRB)

5. Brachioradialis

The radial nerve divides into a deep (mostly motor) branch, which becomes the posterior interosseous nerve (PIN), and a superficial branch. The PIN innervates:

1. Extensor digitorum

2. Supinator muscle

3. Extensor digiti minimi (EDM)

4. Extensor carpi ulnaris (ECU)

5. Abductor pollicis longus (APL)

6. Extensor pollicis longus (EPL)

7. Extensor pollicis brevis (EPB)

8. Extensor indicis proprius (EIP)

Sensory innervation includes:

1. Posterior cutaneous nerve (arm and forearm)

2. Superficial branch radial nerve (SBRN)

3. Dorsal digital branch

The following tests can quickly assess the radial nerve and its motor and sensory functions:

1. Motor function: Thumb extension against resistance

2. Sensory function: Two-point discrimination on the dorsum of the thumb

Nevertheless, a thorough physical exam is always required. Radial nerve injuries have distinct signs and symptoms depending on where and how the nerve has been injured.