The basics: Diagnosing carpal tunnel syndrome

Dr Julian Spinks takes a look at the causes and symptoms of carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is the most common focal peripheral neuropathy. It is caused by compression of the median nerve as it passes through the carpal tunnel. This compression may arise from local trauma or space-occupying lesions of the wrist.

The prevalence for proven disease is 3 per cent but some studies suggest the real prevalence may be above 7 per cent.

Approximately three times as many women as men are affected. The characteristic features of CTS are pain, numbness and tingling of the hand and fingers following the distribution of the median nerve — the radial side of the palm and back of the hands together with the thumb, index and middle finger.
 
The amount of involvement of the ring finger is variable.

The symptoms may be bilateral, but often the dominant side is affected more severely.

Some patients experience pain and paraesthesia in the forearm, elbow or shoulder. In severe cases the patient may also complain of reduced grip.

The pain is often worse at night, causing the patient to wake and shake their hand to relieve the symptoms.

Other patients may notice that certain hand positions or activities, such as typing or driving can exacerbate the condition. Initially symptoms may be episodic, but they may become continuous. Associated conditions include obesity, thyroid disease, rheumatoid arthritis, renal dialysis and diabetes.

Diagnosis
The differential diagnosis includes cervical spondylosis, disc disease and general peripheral neuropathy.
 
The patient may exhibit sensory loss in the distribution of the median nerve. There may also be wasting of the LOAF muscles: lumbricals (first and second), opponens pollicis, abductor pollicis brevis and flexor pollicis brevis.

Clinical tests include Tinel’s test, which involves tapping over the median nerve in the carpal tunnel; Phalen sign, reproduction of the symptoms by full flexion or extension at the wrist for 60 seconds; carpal compression, where direct pressure is placed over the carpal tunnel for 30 seconds; and square wrist sign — the ratio of wrist thickness to wrist width is >0.7.

Laboratory tests for associated conditions, such as thyroid disease, might be clinically indicated. Nerve conduction studies are considered the diagnostic gold standard for CTS but it is worth noting that these are negative in one third of patients with a history strongly supportive of the condition and positive in nearly 20 per cent of asymptomatic controls.

Management
Many patients can be managed in primary care. Associated conditions should be treated first.

Wrist splints can be worn which hold the wrist in a neutral position. The splint may be worn full time or just at night.

Oral steroids have been shown to give short-term relief compared with placebo.

Local corticosteroid injections are another commonly-used intervention in CTS.

Referral for consideration for surgery is appropriate in patients with initial severe symptoms, such as muscle weakness. One third of patients with CTS will have spontaneous resolution of the problem within six months. Following surgery, two thirds of patients are cured.

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