Page 347 - Medicine and Surgery

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Chapter 7: Disorders of cranial and peripheral nerves 343

under local or regional anaesthetic. Treatment of under- axilla (crutch palsy). Radial nerve lesions cause weakness
lying cause may relieve symptoms. in the brachioradialis and triceps muscles.

Clinical features
Ulnar nerve lesions
Wrist drop and sensory loss over the back of the hand at
Definition the base of the thumb (the anatomical snuffbox). If there
The ulnar nerve arises from the brachial plexus and sup- is paralysis of triceps (weakness of elbow extension), this
plies most of the intrinsic muscles of the hand. is evidence of a lesion above the upper third of the upper
arm, e.g. in the axilla. Low lesions, i.e. at the elbow result
Aetiology/pathophysiology in failure to extend the metacarpophalangeal joints.
Most injuries occur at the elbow, although open wounds
can arise anywhere. The ulnar nerve passes down the Management
anterior medial aspect of the upper arm and wraps pos- Compression due to crutch palsy or Saturday night palsy
teriorly round the medial epicondyle of the humerus maytakeupto3monthstorecover.Openwoundsshould
where it is vulnerable to fracture of the elbow or chronic be explored immediately with nerve repair or graft.
pressure. It enters the hand on the ulnar side, and can be Other trauma should be given 6 weeks, with surgery if
damaged by pressure or lacerations at the wrist. there is no sign of recovery.

Clinical features Prognosis
Low lesions (at wrist): There is wasting of all the small Lesions that do not recover can often be overcome by

muscles of the hand except the thenar eminence and suitable tendon transfers.
there is a clawing of the ring and little fingers. Sensa-
tion is lost over the ulnar one and a half fingers.
High lesions (at elbow): The claw deformity is less
Sciatic nerve lesions
due to paralysis of the ulnar side of flexor digitorum
Definition
profundus.
The sciatic nerve (L4–5, S1–3) is a branch of the lum-
bosacral plexus and the largest nerve in the body. It
Management supplies most of the muscles and cutaneous sensation
If the ulnar nerve is severed, repair is may be attempted, of the leg, so that sciatic nerve lesions cause serious
stretching can be avoided by transposing the nerve to the disability.
front of the elbow. Failure of recovery can be overcome
by tendon transfer. Nerve entrapment is treated with
Aetiology/pathophysiology
decompression and transposition of the nerve.
Division of the sciatic nerve occurs occasionally in pene-
trating injuries. Traction injuries occur more commonly
Radial nerve lesions in association with fractures of the pelvis or hip dislo-
cations. It is most frequently injured by badly placed
Definition intramuscular injections in the gluteal region (avoided
The radial nerve supplies the extensor muscles of the by injecting into the upper outer quadrant of the but-
upper arm and forearm. It is a branch of the brachial tock). It supplies all the muscles of the lower leg, some
plexus. of the hamstrings, and most of the sensation of the calf,
as well as the skin on the sole and lateral side of the
Aetiology foot.
Injuries to the radial nerve may occur due to elbow In most sciatic nerve lesions, the common peroneal
fracture/dislocations, in the upper arm due to humerus nerve component is most affected, probably because
fractures or prolonged pressure due to hanging an arm its nerve fibres lie most superficial in the sciatic nerve
over the back of a chair (Saturday night palsy), or in the trunk.