Radial Nerve Special Tests

The radial nerve is tested clinically through a combination of motor function tests, provocation/stress tests targeting specific entrapment sites, and sensory tests. The approach depends on which segment of the nerve is suspected.

1. Motor Function Tests

These screen for the level of radial nerve injury by testing muscles in sequence from proximal to distal.

Muscle	Test	Level Tested
Triceps brachii	Elbow extension against resistance	Radial nerve in axilla/proximal arm
Brachioradialis	Elbow flexion in mid-pronation	Radial nerve proper (mid-arm)
ECRL / ECRB	Wrist dorsiflexion (extension)	Radial nerve / superficial PIN
Extensor digitorum communis	Finger MCP hyperextension against resistance	PIN (posterior interosseous nerve)
Extensor pollicis longus	Thumb extension against resistance	PIN
Abductor pollicis longus	Thumb abduction	PIN
Extensor carpi ulnaris	Wrist extension in ulnar deviation	PIN

How to test finger MCP extension (EDC): Place the patient's palm flat on a table with fingers extended, then ask them to lift each digit while keeping the palm flat. The interossei cannot hyperextend the MCPs, so if extension is present, PIN is intact. - Tintinalli's Emergency Medicine

Wrist drop = classic sign of high radial nerve palsy (inability to extend wrist + fingers). Triceps is usually preserved with mid-humeral lesions.

2. Radial Tunnel Syndrome - Provocation Tests

Radial tunnel syndrome involves compression of the PIN (typically at the Arcade of Frohse) causing lateral proximal forearm pain without significant motor weakness. Maximum tenderness is 3-4 cm distal to the lateral epicondyle (distinguishing it from lateral epicondylitis, where tenderness is directly over the condyle).

a) Resisted Long-Finger (Middle Finger) Extension Test

Patient extends the long finger at the MCP joint against examiner resistance with the elbow extended
Positive: Reproduces pain in the radial tunnel / proximal forearm
This is the most specific provocation test for radial tunnel syndrome

b) Resisted Forearm Supination Test

Patient supinates the forearm against resistance
Positive: Reproduces pain over the radial tunnel
Both resisted long-finger extension and resisted supination are the key provocative tests for this condition - Miller's Review of Orthopaedics 9th Ed

c) Pressure/Palpation Test

Direct compression over the radial nerve/PIN beneath the extensor mass at and just distal to the radial head
Positive: Reproduces the characteristic lateral forearm pain

3. Posterior Interosseous Nerve (PIN) Syndrome

PIN syndrome is the motor variant of radial tunnel entrapment - it presents with actual weakness/paralysis of wrist and finger extensors (unlike radial tunnel syndrome, which is primarily pain).

Wrist Tenodesis Test - Used to differentiate PIN palsy from extensor tendon rupture. Passive wrist flexion should produce passive finger extension via tenodesis effect. In PIN palsy, this effect is preserved but active extension is absent; in tendon rupture, tenodesis is also lost. - Miller's Review of Orthopaedics 9th Ed
Note: ECRL and ECRB may be spared (innervated before PIN diverges), so the wrist can deviate radially but not extend in neutral - a useful localizing sign.

4. Wartenberg Syndrome (Cheiralgia Paresthetica) Tests

Wartenberg syndrome = compression of the superficial branch of the radial nerve (SBRN) between the brachioradialis and ECRL tendons in the distal forearm, causing pain and paresthesias over the dorsoradial hand.

a) Forced Forearm Pronation Test

The examiner forcefully pronates the patient's forearm and holds it for 60 seconds
Positive: Reproduces pain/paresthesias over the dorsoradial hand and thumb
Mechanism: scissors-like compression of the SBRN between the BR and ECRL tendons during pronation - Miller's Review of Orthopaedics 9th Ed

b) Tinel's Sign over the SBRN

Percussion over the nerve as it emerges from between the BR and ECRL tendons (~9 cm proximal to radial styloid)
Positive: Tingling/electric shock in the dorsoradial hand distribution

c) Finkelstein Maneuver

Also positive in Wartenberg syndrome due to close proximity of the SBRN to the 1st dorsal compartment; distinguishing from De Quervain's may require localization of maximum tenderness (more volar/proximal in Wartenberg)

Classic complaint: Unable to wear a wristwatch or tight jewelry due to pain over the nerve. - Campbell's Operative Orthopaedics 15th Ed

5. Sensory Examination

The sensory territory of the radial nerve:

Superficial radial nerve: Dorsum of thumb, index, long finger, and radial half of ring finger; dorsal first web space
Lateral antebrachial cutaneous nerve (from musculocutaneous) covers the distal/lateral forearm, so forearm sensation is preserved even in high radial nerve palsy

Dorsal first web space light touch is the standard quick sensory test for radial nerve integrity - Campbell's Operative Orthopaedics 15th Ed

Two-point discrimination is less useful over the dorsum (fewer receptors than volar fingertips).

Summary Table

Condition	Key Special Test	Positive Finding
High radial nerve palsy	Wrist/finger extension against resistance	Wrist drop, unable to extend MCPs
Radial tunnel syndrome	Resisted long-finger extension	Pain 3-4 cm distal to lateral epicondyle
Radial tunnel syndrome	Resisted supination	Reproduces forearm pain
PIN syndrome vs tendon rupture	Wrist tenodesis test	Tenodesis present = PIN palsy; absent = tendon rupture
Wartenberg syndrome	Forced pronation x60 sec	Dorsoradial paresthesias
Wartenberg syndrome	Tinel over distal forearm	Tingling in dorsoradial hand
Sensory	Dorsal first web space light touch	Absent = superficial radial nerve involvement

Key differentiating points:

Radial tunnel syndrome = pain only, no weakness; tenderness distal to epicondyle
PIN syndrome = motor weakness, pain may or may not be prominent
Wartenberg syndrome = purely sensory, distal forearm/wrist level
High radial nerve palsy (e.g., Saturday night palsy, mid-humeral fracture) = complete wrist drop + loss of finger extension + sensory changes

This is a shared conversation. Sign in to Orris to start your own chat.