Examine this patient's hands.
· Ask the patient about nocturnal pain (commonest cause of hand pain at night).· History of oral contraceptives, rheumatoid arthritis, myxoedema, acromegaly, chronic renal failure, sarcoidosis.· Take a family history (abnormally small size of carpal tunnel runs in families).
· Wasting of the thenar eminence.· Weakness of flexion, abduction and opposition of thumb.· Diminished sensation over lateral three and half fingers.
Proceed as follows
:· Look carefully for scar of previous surgery (hidden by the crease of the wrist).· Percuss over the course of the median nerve in the forearm: patient may experience tingling - this is Tinel's sign.· Ask the patient to hyperextend the wrist maximally for I minute; this may bring on symptoms (dysaesthesia over the thumb andlateral two and half fingers).· Tell the examiner that you would like to:-Examine for underlying causes such as myxoedema, acromegaly and rheumatoid arthritis.Look for cervical spondylosis, frozen shoulder and tennis elbow (these may be associated).-Look for the Cimino-Brescia fistula for haemodialysis (J Neurol NeurosurgPsychiatry 1997; 40:511 ).
This patient has median nerve involvement of the hand with Tinel's sign (lesion) due to carpal tunnel syndrome as a complication ofchronic haemodialysis (aetiology). The patient has disabling tingling and pain at night (functional status).
Mention a few causes of carpal tunnel syndrome.
· Pregnancy.· Oral contraceptives.· Rheumatoid arthritis.· Myxoedema.· Acromegaly.· In chronic renal failure patients on long-term dialysis it is due to [32-microglobulin as amyloid deposition.· Sarcoidosis.· Hyperparathyroidism.· Amyloidosis (e.g. due to multiple myeloma).
How would you treat this condition?
· Diuretics.· Wrist splint and ultrasound treatment (BMJ 1998; 316:731-5).· Local steroid injection should be given proximal to the carpal tunnel (not into the tunnel because it may damage the nerve)(BMJ 1999; 319: 884-6).· Surgical decompression.
How would you confirm the diagnosis?
Nerve conduction studies (increased latency at the wrist on stimulation of the median nerve; the muscle action potential fromabductor pollicis brevis is a valuable diagnostic sign). Rarely, the proximal latency may be normal with a prolonged distal latency dueto an anastomosis between the ulnar and median nerves in the forearm. A negative test thus does not rule the syndrome outabsolutely but calls it into question (J Neurol Neurosurg Psychiatry 1976; 39: 449).
Mention a few clinical diagnostic tests
(Lancet 1990; 335: 393).· Wrist extension test: the patient is asked to extend his wrists for I minute; this should produce numbness or tingling in thedistribution of the median nerve.· Phalen's test: the patient is asked to keep both hands with the wrist in complete palmar flexion for I minute; this producesnumbness or tingling in the distribution of the median nerve.· Tourniquet test: the symptoms are produced when the blood pressure cuff is inflated above the systolic pressure.· Pressure test: if pressure is placed where the median nerve leaves the carpal tunnel, it causes pain.· Luthy's sign: if the skinfold between the thumb and index finger does not close tightly around a bottle or cup because of thumbabduction paresis, this test is regarded as positive.· Durkan's test: direct pressure over the carpal tunnel - the carpal compression test -is more sensitive and specific than the Tineland Phalen sign.
Mention other entrapment neuropathies.
· Meralgia paraesthetica (lateral cutaneous nerve of the thigh trapped under the inguinal ligament).· Elbow tunnel syndrome (ulnar nerve trapped in the cubital tunnel; see p.207).· Common peroneal nerve trapped at the head of the fibula (see p. 211).· Morton's metatarsalgia (trapped medial and lateral plantar nerves causing pain between third and fourth toes).· Tarsal tunnel syndrome (posterior tibial nerve is trapped).· Suprascapular nerve trapped in the spinoglenoid notch.· Radial nerve trapped in the humeral groove.· Anterior interosseous nerve trapped between the heads of the pronator muscle.Jules Yinel (1879-1952), a French neurologist, described it as the 'sign of formication' in his book on nerve wounds. He took anactive part in the French resistance.T.G. Morton (1835-1903), a US surgeon, described this syndrome in 1876.