The symptoms and signs of this condition include paraesthesia (an abnormal sensation, typically tingling or pricking like ‘pins and needles’); numbness; burning sensation; pain; inability to grasp; and an unhealthy texture of the skin of the affected hand. If untreated, wasting of the hand muscles will occur.

Carpal Tunnel Syndrome is due to a compression of the median nerve at the wrist. The median nerve is one of the three principal nerves which control the neurological function of the hand. The other two nerves are the radial nerve and the ulnar nerve, but they are not involved in this condition.

This condition is easy to diagnose and can be treated successfully with a simple neurosurgical procedure.

Causes

The median nerve originates from multiple roots of the cervical spinal cord and then forms a network or plexus, before making a single cord which traverses the armpit, arm, forearm and enters the hand through the compact carpal tunnel at the wrist.

The carpal tunnel is a compact passage formed by small bony pieces of the wrist bound by the thick transverse membrane called flexor retinaculum or transverse carpal ligaments.

The median nerve, tendons and lubricant-filled sleeves go through the carpal tunnel before attachment to the fingers. A swelling of the contents within the carpal tunnel or restriction of the unyielding space can cause increased pressure within it, leading to the compression of the median nerve, thus interfering with its function. This could either be due to mechanical pressure or impairment of the blood supply.

It is, however, not clear why the structures within the carpal tunnel become swollen. But in some patients Carpal Tunnel Syndrome has been associated with the following:

• Hormonal changes — pregnancy, menopause, acromegaly, hypoparathyroidism and oral contraceptives
• Tumours — ganglion of the wrist, lipoma and neurofibroma
• Systemic diseases — gout, rheumatoid arthritis, hypothyroidism and alcoholism
• Mechanical overuse — vibrating machinery, prolonged typing, playing musical instruments
• Trauma-related structural changes — distal radius fracture, oedema, haemorrhage and post-traumatic arthritis
• Anatomy — decreased size of carpal tunnel and thickened flexor retinaculum

More women than men are affected by Carpal Tunnel Syndrome. Even though exact numbers are not known, there are reports which indicate that up to 1% of the population and 5% or more of workers in certain industries requiring repetitive movements of hands and wrist are affected. Around 50% of cases are said to occur when they are in their forties or fifties.

Clinical diagnosis of Carpal Tunnel Syndrome

Getting an accurate history is vital. The patient may complain of a burning pain or numbness of the fingers, with the little finger being spared. The symptoms occur more in the night which may wake up the patient who feels the need to hang the hand over the bed or shake it for relief. The symptoms may radiate up to the arm as far as the elbow and are exacerbated by postures which flex the wrist or elevate the arm.

Over time, fine finger movements may be affected and weakness may occur in the pinch or grip strength. There may be evidence of trophic changes in association with the skin and the soft tissue of the hands such as discolouration, unhealthy texture and trophic ulcers. There could also be wasting of the muscles in the thenar eminence (base of the thumb). The symptoms may be bilateral, with one side being generally worse than the other.

Apart from general, physical and neurological examinations, there are several provocative tests that can be used to elicit the symptoms associated with Carpal Tunnel Syndrome. They are:

• Phalen’s Test which involves holding the wrist at a maximum flexion for 30 seconds. A characteristic median nerve distribution paraesthesia can be elicited with this manoeuvre.
• Tinel’s Test which involves causing percussion over the median nerve at the carpal crease would reproduce paraesthesia in the median nerve.

When diagnosing Carpal Tunnel Syndrome, some other conditions which mimic it need to be ruled out. These conditions include Cervical Disc Herniation; Cervical Spondylosis; Thoracic Outlet Syndrome; Proximal Median Nerve Compression; and Brachial Plexopathy.

The screening tests for Carpal Tunnel Syndrome should include Thyroid Function Test, Rheumatoid Factor, Uric Acid, Antinuclear Factor, Serum Cholesterol, Fasting Blood Sugar, ESR and Chest X-ray.

While Electromyography (EMG)/nerve conduction studies may be helpful in the diagnosis of Carpal Tunnel Syndrome, particularly when the clinical findings are unclear, sometimes they can be negative in a patient with the disorder.

The electrophysiological classification of the condition is:

• Mild – sensory only
• Moderate – sensory and motor
• Severe – Denervation of median nerve intrinsic muscles

Treatment

Simple surgery, performed under local anaesthesia, is the treatment of choice and aims to relieve the compression of the median nerve by the flexor retinaculum overlying the carpal tunnel. It is a day procedure.

The definitive indications for surgery are:

• Rapidly progressive thenar wasting and hand dysfunction.
• Substantial symptoms which cannot be relieved through conservative measures.
• When nerve conduction and electromyographic results suggest severe carpal tunnel compression with clinical confirmation.

The aims of the operation are:

• Division of the entire length of the flexor retinaculum.
• Avoidance of damage to neurovascular structures.
• Pain relief for the patient.
• Relief of sensory disturbances for the patient.
• Ideally, the recovery of motor function and reversion of thenar atrophy following surgery, but in practice surgeons aim to halt the progression of these neurological deficits.

The surgical technique –

A local anaesthetic is given to the site of the surgery at the wrist and a compression tourniquet is applied to the upper arm to achieve a bloodless field. The operation site is marked, prepared and draped, after which a small skin incision, 1cm in length, is made.

Thereafter, the mini self-retained refractor is applied and the rest of the procedure continued under head light vision and surgical loup magnification. The exposure is deepened until the flexor retinaculum can be visualized, with a small incision then being made on the retinaculum until the median nerve is exposed. The retinaculum is separated and divided completely with a pair of small fine scissors, keeping a close eye on the median nerve.

The surgical site is closed with non-absorbable suture material and the operation site covered with cotton padding and crepe bandage with adequate compression.

The post-operative care entails keeping the hand elevated for 24 hours. The patient may be discharged after about two hours of neurosurgical observation. Finger movements have to be done continuously.

While analgesics are given for the pain when necessary, oral antibiotics are prescribed for five days. The sutures are removed after 14 days.

(The writer is a Consultant Neurosurgeon)

 

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