Ulnar nerve palsy

Published on 02/04/2015 by admin

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74 Ulnar nerve palsy

Instruction

Carry out a neurological examination of this patient’s upper limbs.

Salient features

History

• Repeated trivial trauma to the elbow; the patient feels the ‘funny bone’

• Patient may be immobilized in the orthopaedic ward and use the elbows to shuffle in bed

• History of fracture of the upper arm in childhood (supracondylar fractures of humerus in childhood has an insidious course and can result in acute ulnar nerve palsy 20–30 years later: tardy-ulnar palsy).

Examination

• Generalized wasting of the small muscles of the hand.

• There may be features of ulnar claw hand: hyperextension at the metacarpophalangeal joints and flexion at the interphalangeal joints of the fourth and fifth fingers (Fig. 74.1).

• There is weakness of movement of the fingers, except that of the thenar eminence.

• There is sensory loss over the medial one and half fingers.

Fig. 74.1 (A) Benediction posture, with clawing of the fourth and fifth fingers while fingers and thumb are held slightly abducted. (B) Wartenberg’ sign, abduction of the little finger with the hand at rest. (C) Froment’s sign, seen when using the thumb and index finger to pinch an object. (D) Weakness of the ulnar flexor digitorum profundus, inability to completely flex the distal phalanx of the fourth and fifth digits.

Proceed as follows:

• Examine the elbow for scars and signs of osteoarthrosis.

• Comment on the large carrying angle at the elbow, particularly in women (repeated extension and flexion of the arm can result in damage of the olecranon and consequently the ulnar nerve).

Diagnosis

This patient has wasting of the small muscles of the hand and claw hand with sensory loss over the medial one and half fingers (lesion) caused by ulnar nerve palsy following trauma (aetiology). She is unable to button her clothes (functional status).

Advanced-level questions

How would you differentiate between a lesion above the cubital fossa and a lesion at the wrist?

• In lesions above the cubital fossa the flexor carpi ulnaris is involved.

• In lesions at the wrist, the adductor pollicis is involved.

How would you test the flexor carpi ulnaris?

Ask the patient to keep the hand flat on a table with the palm facing upwards and then to perform flexion and ulnar deviation at the wrist.

How would you test the adductor pollicis?

Ask the patient to grip a folded newspaper between the thumb and index finger of each hand so that the thumbs are uppermost—this causes the adductor to contract. When the muscle is paralysed, the thumb is incapable of adequate adduction and becomes flexed at the interphalangeal joint caused by contraction of the flexor pollicis longus (innervated by the median nerve). This is known as Froment’s sign (Fig. 74.1C).

What is ulnar paradox?

The higher the lesion in the upper limb, the lesser is the deformity. A lesion at or above the elbow causes paralysis of the ulnar half of the flexor digitorum profundus, interossei and lumbricals. Thus, the action of the paralysed profundus is not unopposed by the interossei and lumbricals; as a result, the ring and little fingers are not flexed and hence there is no claw, whereas a lesion at the wrist causes an ulnar claw hand.

What causes the ulnar claw hand?

A lesion of the ulnar nerve at the wrist. The little and ring fingers are flexed at the interphalangeal joints and hyperextended at the metacarpophalangeal joints. The index and middle fingers are less affected as the first and second lumbricals are supplied by the median nerve.

How can the ulnar nerve be affected at the wrist?

The deep branch of the ulnar nerve is motor and may be compressed in Guyon’s canal, which runs between the pisiform and hook of the hamate. This results in wasting and weakness of the interossei, particularly the first and the adductor pollicis, but sensation is spared. Also the hypothenar muscles are usually spared, although the third and fourth lumbricals may be affected. The nerve may be compressed in Guyon’s canal by a ganglion, neuroma or repeated trauma. Surgical exposure of the nerve may be necessary when there is no history of trauma.

What is the most common cause of an ulnar nerve lesion at the elbow?

It is caused by compression of the nerve by the fibrous arch of the flexor carpi ulnaris (the cubital tunnel), which arises as two heads from the medial epicondyle and the olecranon.

What you understand by ‘tardy ulnar nerve palsy’?

This occurs when injuries or arthritic changes at the elbow cause a delayed or slowly progressive involvement of the ulnar nerve.

How would you rapidly exclude an injury to a major nerve in the arm?

• Radial nerve: test for wrist drop

• Ulnar nerve: test for Froment’s sign (see above)

• Median nerve: Ochsner’s clasping test.

R von Volkmann (1830–1889), Professor of Surgery in Halle, Germany.

Augusta Déjérine-Klumpke (1859–1927), a French neurologist, was the first woman to receive the title ‘Internes des Hôpitaux’ in 1877.

Jules Froment (1876–1946), Professor of Clinical Medicine, Lyons, France.

AJ Ochsner (1896–1981), a US surgeon, also investigated the role of tobacco in lung cancer.

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