Review Article
Volume 2, No.2
October 1998
 
 Dietmar Stolke

 Translation
 Khalad Al Moutaery
 Neurosurgery Clinic &
    Polyclinic
 University of Essen
 Germany
 Correspondence:
 Prof Dietmar Stolke
 Neurosurgery Clinic &
     Polyclinic
 University of Essen
 Germany
 Fax: (49) 201 723 5909  
 
Radial Nerve Compression Syndromes

   INTRODUCTION

The radial nerve is more prone to injury because of its spiral course along the humerus. Fracture or continuous pressure is the most often aetiological factors seen. Radial nerve injuries constitute 70% of the nerve injuries in the arm and 35% of injuries in the forearm.

ANATOMY

The radial nerve is the direct continuation of the posterior cord of brachial plexus. In the axilla it is placed behind the axillary artery and in front of the axillary nerve teres major and latissimus dorsi. Leaving the axilla it heads towards the lower border of teres major, it inclines downwards and backwards through the interval between the long and medial heads of triceps and comes to lie on the oblique groove on the posterior aspect of humerus. Although the majority of the branches of this long nerve arise in the arm and forearm its first branches given off in the axilla. The posterior cutaneous nerve of the arm winds backwards round the medial side of the long head of triceps to supply a small skin area on the posterior aspect of the arm at the level of insertion of deltoid.

Reference for nerve branches arising:
In the arm - 1
In the elbow - 2
In the forearm - 3
In the hand - 3a

The following muscle nerve supply emanates in the region as follows:
Triceps brachii - 1
Brachioradialis - 1
Posterior cutaneous nerve of the arm - 1
Extensor carpi radialis longus - 2
Supinator - 3
Superficial branches of radial nerve - 3
Extensor di torum - 3a
Extensor digiti Minimi- 3a
Abductor pollicis longus - 3a
Extensor pollicis longus - 3a
Extensor indices - 3a

In the upper third of the forearm the radial nerve enters through the supinator groove where the posterior interosseous (3a) comes out and gives off motor branches to the extensor of the hand Superficial branch of the radial nerve supplies the skin of the lateral aide of the dorsum of the hand and the lateral three and a half fingers.

Site of Lesion

1.
 Radial nerve injuries in the axilla
2.
 Radial nerve injuries in the radial groove
3.
 Wartenberg's Syndrome
4.
 Cheiralgia Paresthetica
5.
 Radial nerve injuries in the supinator tunnel

1. Radial Nerve Injuries in the Axilla
In the axilla the nerve may be injured by pressure of the upper end of badly fitting crutch pressing up in to the armpit or by the drunkard falling asleep with his arm over the back of a chair. It may also be badly damaged in the axilla by fractures or dislocations of the upper end of the humerus. When the humerus is displaced downwards in dislocation of the shoulder the radial nerve which is wrapped around the back of the shaft of the bone is pulled downwards stretching the nerve in the axilla excessively.

Motor: Triceps anconeus and long extensor of the wrist are paralysed. The patient is unable to extend the elbow joint, wrist joint and fingers. Drop or flexion of the wrist occurs as a result of the unopposed flexor muscles of the wrist.

Sensory: There is a small loss of skin sensation down the posterior surface of the lower part of the arm and down a narrow strip on the back of the forearm. There is also a variable area of sensory loss on the lateral part of the dorsum of the hand. The dorsal surface of the roots of the lateral three and one half fingers. The area of total anaesthesia is relatively small due to the overlap of sensory innervation by adjacent nerves.

2. Radial Nerve Injuries in the Radial Groove
This is the most common lesion of the. radial nerve resulting because of the fracture of the shaft of humerus, callus formation, pressure on the back of the arm on the edge of the operating table in an unconscious patient and prolonged application of tourniquet. The injury to radial nerve occurs most commonly in the distal part of the groove beyond the origin of the nerve to the triceps, anconeus and beyond the origin of the cutaneous nerve.

Motor: With intact forearm extension, weakness of forearm flexion, weakness of hand extension as well as finger extension.

Sensory: Variable anaesthesia is present in the radial part of the forearm and back of the hand.

3. Wartenberg's Syndrome
Division of the superficial radial nerve which is sensory as a result of stab injury, iatrogenic or shunt operation for dialysis patients. It can also result because of pressure from handcuffs, tight bangles, tumour like ganglion, idiopathic or diabetes mellitus.
Figure 3 — Diagramic representation of radial nerve formation and distribution

4. Cheiralgia Parasthetica
Lesion of the dorsal digital branch of the superficial radial nerve with compression on the radial side of the thumb. It is seen because of the vibratory and stereotypic movements in industrial workers.

5. Radial Nerve Injuries in Supinator Tunnel
Motor: Pure motor lesion leads to no sensory disturbances. Intact forearm extension and flexion with intact hand extension. Only weakness of the ulnar hand extension and weakness of finger extensors. It may be damaged in fracture of the proximal end of the radius or during dislocation of the radial head. Nerve supply to the supinator and extensor carpi radialis longus will be undamaged and because the later muscle is powerful it will keep the wrist joint extended and this wrist drop will not occur. There will be no sensory loss since this is a motor nerve.

Other causes of injury include compression by a tumour, lipoma, rheumatic disease and changes of the lower end of the extensor carpi radialis brevis muscle.
 


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