UPPER PLEXUS LESION (C5C6)
Traction on the arm at birth (Erb-Duchenne paralysis) or falling on the shoulder may damage the upper part (C5C6) of the plexus. Deltoid
Supraspinatus f- paralysed.
Brachialis elbow flexors - also paralysed.
Adductors of shoulder - mildly affected.
When damage to C5C6 is more proximal, nerve to rhomboids and long thoracic nerve may be affected.
POSTERIOR CORD LESION (C5C6C7C8)
Extensors of elbow (triceps)
Extensors of wrist (extensor carpi radialis longus f paralysed and brevis, extensor carpi ulnaris) Extensors of fingers (extensor digitorum)
LOWER PLEXUS LESION (C8T,)
Forced abduction of the arm at birth (Klumpke's paralysis) or trauma may produce damage to the lower plexus. This results in paralysis of the intrinsic hand muscles producing a claw hand, CgT] sensory loss and a Horner's syndrome (page 141) if the T, root is involved.
n.b. A combined ulnar and median nerve lesion will produce a similar picture in the hand but with involvement also of flexor carpi ulnaris and pronator teres.
TOTAL BRACHIAL LESION
This results in complete flaccid paralysis and anaesthesia of the arm.
The presence of a Horner's syndrome indicates proximal Ti nerve root involvement.
n.b. When trauma is the cause of brachial paralysis, early referral to a specialist unit with experience in the surgical repair of plexus injuries is advised.
Sensory loss in a Tj distribution.
Wasting and weakness of thenar and occasionally interosseous muscles. Signs of vascular compression:
- Unilateral Raynaud's phenomenon.
- Pallor of limb on elevation.
- Brittle trophic finger nails.
- Loss of radial pulse in arm on abduction and external rotation at the shoulder or on bracing the shoulders — arson's sign.
- Subclavian venous thrombosis may occur, especially after excessive usage of arm.
Plain radiology of the thoracic outlet may reveal a cervical rib or prolonged transverse process. Nerve conduction/electromyography will distinguish this from other peripheral nerve lesions. Arteriography or venography is occasionally necessary if there are obvious vascular problems.
In middle-aged people with poor posture and no evidence of abnormality on plain radiology, neck and postural exercises are helpful.
In younger patients with clinical and electrophysiological changes supporting the radiological abnormalities, exploration and removal of a fibrous band or rib may afford relief.
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