Treatment Surgical division of the carpal ligament with decompression of the nerve is curative but is required only in severe and protracted cases. Splinting of the wrist to limit flexion almost always relieves the discomfort but denies the patient the full use of the hand for some time. It is a useful temporizing measure for a few weeks, as is the injection of hydrocortisone into the carpal tunnel. Studies of oral corticosteroids give conflicting results. Treatment of an underlying condition such as arthritis, hypothyroidism and possibly diabetes, is often helpful. Some patients have benefited, paradoxically, from the stopping of corticosteroids or estrogen. Also, some practitioners favor the use of nonsteroid anti-inflammatory medication, but we have been generally unimpressed with the results. Most often, splinting and local steroid injections are very satisfactory in the short term, especially if the symptoms are of recent onset.
Another less common site of compression of the median nerve is at the elbow, where the nerve passes between the two heads of the pronator teres, or just above that point behind the bicipital aponeurosis. It gives rise to the “pronator syndrome,” in which forceful pronation of the forearm produces an aching pain (see Table 43-8). There is weakness of the abductor pollicis brevis and opponens muscles and numbness of the first three digits and palm.
This nerve is derived from the eighth cervical and first thoracic roots. It innervates the ulnar flexor of the wrist, the ulnar half of the deep finger flexors, the adductors and abductors of the fingers, the adductor of the thumb, the third and fourth lumbricals, and muscles of the hypothenar eminence. Complete ulnar paralysis is manifest by a characteristic clawhand deformity; wasting of the small hand muscles results in hyperextension of the fingers at the metacarpophalangeal joints and flexion at the interphalangeal joints. The flexion deformity is most pronounced in the fourth and fifth fingers, as the lumbrical muscles of the second and third fingers, supplied by the median nerve, counteract the deformity. Sensory loss occurs over the fifth finger, the ulnar aspect of the fourth finger, and the ulnar border of the palm.
The ulnar nerve is vulnerable to pressure in the axilla from the use of crutches, but it is most commonly injured at the elbow by fracture or dislocation involving the joint. Delayed (“tardive”) ulnar palsy may occur many months or years after an injury to the elbow that had resulted in a cubitus valgus deformity of the joint. Because of the deformity, the nerve is stretched in its groove over the ulnar condyle and its superficial location renders it vulnerable to compression. A shallow ulnar groove, quite apart from abnormalities of the elbow joint, may expose the nerve to compressive injury from more innocuous situations such as prolonged resting of the arm on the side of a chair or even excessive flexion of the elbow. Anterior transposition of the ulnar nerve is a simple and effective form of treatment for these types of ulnar palsies. Compression of the nerve may occur just distal to the medial epicondyle, where it runs beneath the aponeurosis of the flexor carpi ulnaris (cubital tunnel). Flexion at the elbow causes a narrowing of the tunnel and constriction of the nerve. This type of ulnar palsy is treated by incising the aponeurotic arch between the olecranon and medial epicondyle. Yet another site of ulnar nerve compression is in the ulnar tunnel at the wrist. Prolonged pressure on the ulnar part of the palm may result in damage to the deep palmar branch of the ulnar nerve, causing weakness of small hand muscles but no sensory loss. This site is most often implicated in patients who hold tools or implements tightly in the hand for long periods (we have seen it in machinists and professional cake decorators). The lesion is localizable by nerve conduction studies.