Explainer: what is carpal tunnel syndrome and what happens if I get it?

It often begins as an easily dismissed tingle in the thumb or an ache in the wrist. Building slowly but persistently to a searing, tearing pain from the wrist to the fingers. Culminating in sleepless nights, workless days and a numb but simultaneously excruciating, useless hand. Carpal tunnel syndrome is a painful and disabling condition. It’s also very common.

The carpal tunnel itself is a tunnel in the wrist made up of bony structures that are the base and walls, with a roof constructed by a dense fibrous sheet called the flexor retinaculum.

Through this tunnel courses a bundle of nerves, blood vessels and tendons that are the cables of supply to the hand. The syndrome is a result of pressure on the all important median nerve that travels through this space-limited tunnel.

The median nerve supplies sensation and strength to most of the thumb, several fingers and part of the palm. It is thought increased swelling or fluid in the carpal tunnel places pressure on this nerve resulting in the distressing symptoms experienced. Swelling may occur for several reasons, for example with repetitive hand movements or in pregnancy.

Who’s at risk?

Carpal tunnel syndrome has been reported to account for more days off work than any other occupation-related injury. Some 7.8% of the US working population are estimated to be affected and a UK study estimated an annual incidence of 120 per 100,000 women and 60 per 100,000 men.

An audit performed in general practice in Australia found there are about 195,000 appointments annually with patients for carpal tunnel syndrome.

It seems to occur more commonly in women, particularly during pregnancy. Although the mechanism is unclear, it is thought a combination of hormonal factors as well as increased fluid in the body of a pregnant woman increases the pressure in the carpal tunnel.

While we may not be able to modify these aspects, there are risk factors that may be more amenable. Increased body mass index and obesity increase your risk of developing this syndrome, as does diabetes. Some data also associates increased occupational risk, particularly tasks requiring hand force or repetitive wrist movement.

How do I know if I have it?

Sufferers of carpal tunnel syndrome might feel tingling or pain in their fingers or hand. It’s often intermittent at the start – just a nuisance – and then it gets worse. Sufferers may experience sharp pain and numbness that wakes them at night. Shaking the hand might help it settle, but not always. At its most severe, the hand may be weak, holding things is difficult, lifting things is out of the question.

Discussing these symptoms with your doctor is important and you may need to have a nerve conduction study. This study involves testing the function of the nerves in your hand. It can be uncomfortable, but it is safe. More importantly, it tells you if your nerve is trapped in the tunnel.

What can I do?

There are several options for treatment. A wrist splint can be helpful; it supports your wrist and reduces trauma to the nerve. Different medications and a local steroid injection to help with the pain can also be useful.

If things don’t improve, you may go on to have carpal tunnel release surgery. The procedure aims to loosen the lid on the tunnel and relieve the pressure on the nerve. It’s not as scary as it sounds and is the most commonly performed hand surgery. Surgery under local anaesthetic or via endoscopic means (“key hole”) are even available now.

Will it get better?

Severity has historically been the instigator for treatment. We often leave things until they have to be done, surgery especially.

However a worse outcome is associated with longer duration of symptoms, particularly over six months. If the nerve is too far compressed, it may not rebound, despite surgery. So if your symptoms are persistent and start to bother you, talk to your local doctor.

Vinojini Vivek is affiliated with and employed by Melbourne Health.