The carpal tunnel syndrome

This occurs more often in women than in men, and is often worse during pregnancy, and before menstruation. It is the result of pressure on a patient's median nerve, as it passes through her carpal tunnel, on the front of her wrist. It causes: (1) Pain, pins and needles and reduced sensation in the distribution of her median nerve (her thumb, her index and her middle finger, and the radial side of her ring finger). (2) Weakness and wasting of the muscles of her thenar eminence; her hypothenar muscles are spared. (3) Pain in her wrist, usually referred pain to her lower forearm, and sometimes even pain referred to her elbow and upper arm. Her pain is worse at night, and she may get some relief by hanging it out of bed. Tapping over her flexor retinaculum (Tinel's sign) may bring on her symptoms.

Fig. 27-14a THE CARPAL TUNNEL SYNDROME. A, and B, landmarks for the incision. C, the median nerve with an annular constricting ring round it, caused by pressure from the edge of the flexor retinaculum. D, the distal and E, the proximal row of carpal bones and the carpal tunnel.

H, the hamate. C, the capitate. T, the trapezium. T[,2], the trapezoid. L, the lunate. S, the scaphoid. Tq, the triquetrum. P, the pisiform.

1, the median nerve. 2, the ulnar nerve and artery. 3, the muscular branch of the median nerve. 4, the profundus tendons. 5, the superficialis tendons. 6, flexor pollicis longus. 7, flexor carpi radialis. 8, the pisiform bone. 9, the hook of the hamate. 10, the tuberosity of the scaphoid. 11, the tuberosity of the trapezium. After ''Grant's Method of Anatomy', (9th edn 1975), edited by JV Basmajian), Figs. 32.17 and 32.20. Williams and Wilkins, permission requested.

CARPAL TUNNEL SYNDROME NON-OPERATIVE TREATMENT. (1) Reduce the patient's oedema with a thiazide, such as hydrochlorthiazide 25 to 50 mg twice daily during pregnancy. Don't operate while she is pregnant, unless her symptoms are severe. (2) Encourage her to lose weight. (3) Inject her carpal tunnel with hydrocortisone suspension 2.5 ml and lignocaine 2.5 ml.

INDICATIONS FOR SURGERY. (1) Wasting of the muscles of her thenar eminence. (2) Failure of non-operative treatment.

ANAESTHESIA. Axillary block (A 6.18), intravenous forearm block (6.19) or general anaesthesia (A 11.3).

METHOD. If you cannot refer her, apply a tourniquet to produce a bloodless field (3.9). Make an L-shaped incision over the creases on the front of her wrist, as in Fig. 27-14a. Incise longitudinally for 4 cm in her thenar crease, and then transversely for 2 cm in her wrist crease. Divide her flexor retinaculum in the line of her arm. Look for her median nerve, but don't injure it. Opposite the proximal edge of her retinaculum you should see an incomplete annular depression, most marked anteriorly, which is the site of pressure. Don't sew her deep tissues. Sew up her skin only with 2/0 or 3/0 monofilament. Apply a pressure dressing for 48 hours. Raise her arm in a roller towel (B, 75-1).

POSTOPERATIVELY, watch the circulation in her hand hourly; if there is any problem with this, remove all dressings. She will probably find that her pain is relieved immediately.