Carpal Tunnel Syndrome: Symptoms, Causes and Treatment

What is carpal tunnel syndrome?

The carpal tunnel is a narrow passage in your wrist, with just enough room for the tendons that bend your fingers and for the median nerve. That nerve carries feeling from your thumb and most of the next two fingers. When the tendons swell or thicken, or the tunnel narrows, the nerve gets squeezed.¹

It is the most common trapped nerve condition in the world.²

Carpal tunnel symptoms

• Tingling, pins and needles or numbness in the palm, thumb, index finger and middle finger
• Pain in the wrist or hand that can spread up the arm
• Symptoms that are worse at night, and often wake you
• A weak grip, or dropping things
• Fingers that feel swollen¹

The little finger is supplied by a different nerve and is usually spared. Both hands can be affected, and the hand you use most is often worse.¹

Not all tingling hands are carpal tunnel syndrome. In a Swedish population study, 14 per cent of adults reported pain, numbness or tingling in that part of the hand, but only about 1 in 5 of them had carpal tunnel syndrome confirmed by examination and nerve testing. Overall, 2.7 per cent of the population had confirmed carpal tunnel syndrome.³

What causes it?

Often there is no single cause.¹ Things that raise the risk include:

• Being female and aged 40 to 60¹
• Excess weight. A meta-analysis of 58 studies found that being overweight raised the risk about 1.5 times, and obesity doubled it⁴
• Diabetes. Both type 1 and type 2 diabetes raise the risk⁵
• Pregnancy. The body holds more fluid, which causes swelling in the tunnel¹
• An underactive thyroid, rheumatoid arthritis and other forms of arthritis¹
• A wrist injury, such as a fracture or sprain¹
• Forceful or repetitive hand use, including vibrating tools¹

Does typing cause carpal tunnel syndrome?

The evidence is mixed. A meta-analysis found that computer users had no higher rate of carpal tunnel syndrome than the general population. Among office workers, though, those who used a computer or mouse the most had higher rates than those who used them least.⁶ The question isn’t settled.

Carpal tunnel in pregnancy

It is common in pregnancy and usually goes away after the baby is born.¹ Not always, though. A systematic review found that more than half of affected women still had some symptoms a year later, and about 30 per cent at three years.⁷ If your symptoms carry on after the birth, have them checked.

How is it diagnosed?

Your doctor will ask about your symptoms and examine your hand. They may order blood tests to look for causes such as a thyroid problem or rheumatoid arthritis, and nerve conduction tests, which measure how quickly signals travel along the median nerve through the wrist.¹

Carpal tunnel treatment

Wrist splint

A splint keeps the wrist straight, which keeps pressure in the tunnel low. It is mainly worn at night.¹ It is cheap and safe, and it is the usual first step.

The evidence is modest. A Cochrane review of 29 trials found that splinting may give little or no benefit for symptoms in the first three months compared with no treatment, though one trial found people were more likely to report overall improvement with a night splint.⁸

Treat the cause

Managing a condition such as diabetes or an underactive thyroid, and changing activities that bring on symptoms, can help.¹

Injection

An injection into the wrist can ease symptoms.¹ The relief may be temporary.

Surgery

Carpal tunnel release is usually considered when symptoms are severe, getting worse, or haven’t improved with other treatment. The surgeon cuts the ligament that forms the roof of the tunnel, which gives the nerve more room.¹

• In a Dutch trial, 80 per cent of people who had surgery were improved at three months, compared with 54 per cent who used a splint. At 18 months it was 90 per cent against 75 per cent, and by then four in ten of the splint group had gone on to have surgery.⁹
• A 2024 Cochrane review found that surgery probably leads to a higher rate of improvement than splinting over the long term, although the average difference in symptom scores was small.¹⁰
• The results last. In a follow-up study an average of 13 years after surgery, 88 per cent of patients were satisfied and 74 per cent said their symptoms had gone completely.¹¹

What happens if it’s not treated?

Mild cases can settle. But if the nerve stays compressed, symptoms can get worse and the damage can become permanent, with weakness in the muscles of the hand.¹ Constant numbness and wasting of the muscle at the base of the thumb are signs not to wait.

When to see a doctor

• Tingling or numbness in your hand that keeps coming back or wakes you at night
• Weakness, clumsiness or dropping things
• Numbness that is constant
• Symptoms that continue after pregnancy

Seek help urgently for weakness in the arm, a sudden change in feeling, or pain that is severe or getting worse.¹

References

1. healthdirect. Carpal tunnel syndrome.
2. Padua L, Coraci D, Erra C, et al. Carpal tunnel syndrome: clinical features, diagnosis, and management. Lancet Neurol. 2016;15(12):1273-1284.
3. Atroshi I, Gummesson C, Johnsson R, et al. Prevalence of carpal tunnel syndrome in a general population. JAMA. 1999;282(2):153-8.
4. Shiri R, Pourmemari MH, Falah-Hassani K, et al. The effect of excess body mass on the risk of carpal tunnel syndrome: a meta-analysis of 58 studies. Obes Rev. 2015;16(12):1094-104.
5. Pourmemari MH, Shiri R. Diabetes as a risk factor for carpal tunnel syndrome: a systematic review and meta-analysis. Diabet Med. 2016;33(1):10-6.
6. Shiri R, Falah-Hassani K. Computer use and carpal tunnel syndrome: A meta-analysis. J Neurol Sci. 2015;349(1-2):15-9.
7. Padua L, Di Pasquale A, Pazzaglia C, et al. Systematic review of pregnancy-related carpal tunnel syndrome. Muscle Nerve. 2010;42(5):697-702.
8. Karjalainen TV, Lusa V, Page MJ, et al. Splinting for carpal tunnel syndrome. Cochrane Database Syst Rev. 2023;2(2):CD010003.
9. Gerritsen AA, de Vet HC, Scholten RJ, et al. Splinting vs surgery in the treatment of carpal tunnel syndrome: a randomized controlled trial. JAMA. 2002;288(10):1245-51.
10. Lusa V, Karjalainen TV, Pääkkönen M, et al. Surgical versus non-surgical treatment for carpal tunnel syndrome. Cochrane Database Syst Rev. 2024;1(1):CD001552.
11. Louie DL, Earp BE, Collins JE, et al. Outcomes of open carpal tunnel release at a minimum of ten years. J Bone Joint Surg Am. 2013;95(12):1067-73.