Carpal tunnel syndrome is compression of the median nerve as it passes through the wrist. The nerve travels through a narrow passage called the carpal tunnel, formed by the small wrist bones on one side and a band of tissue, the flexor retinaculum, on the other. When pressure inside that tunnel rises, the nerve is what suffers.
The median nerve supplies feeling to the thumb, index finger, and middle finger, and often half of the ring finger. This is why symptoms are typically felt in these fingers, and not the little finger. The exact pattern varies between individuals, because the area each person's median nerve supplies is not identical. Some people feel it only in the thumb, index, and middle fingers. Others feel it through the whole ring finger, or describe it spreading into the whole hand. This variation is normal.
The same study found that diabetes, rheumatoid arthritis, and an underactive thyroid were all linked to a higher chance of developing carpal tunnel syndrome, as was a higher body weight. None of these conditions cause carpal tunnel syndrome on their own. Each appears to make the tunnel more likely to become tight enough to compress the nerve.
The carpal tunnel is at its narrowest when the wrist is bent and the fingers are curled. Bending the wrist alone tightens the tunnel. Curling the fingers adds to this: small muscles inside the palm, called the lumbricals, move further into the tunnel as the fingers close.
During the day, the wrist is generally kept close to a neutral position. Overnight, once the muscles relax during sleep, the flexor muscles on the palm side of the forearm are naturally stronger than the extensor muscles on the back of the forearm. They take over, and the wrist and fingers curl, regardless of how a person fell asleep. This is why symptoms wake patients at night. The same mechanism explains why holding a phone or reading with the wrists bent can bring symptoms on during the day.
Diagnosis is established first by the description of symptoms, then by examination findings. A nerve conduction study is only needed where the history and the examination signs are not consistent with each other, or where the pattern is unusual, such as symptoms spreading into the little finger.
The examination includes several checks. Sensation in the fingers is tested, though this can be a late sign and may not yet be present in early cases. Tapping over the nerve at the wrist, known as Tinel's test, produces a shock-like sensation into the fingers when positive. Pressing on the nerve while bending the wrist, known as Durkan's test, reproduces the patient's usual numbness within about thirty seconds when positive. Some surgeons also use a supplementary test called the scratch collapse test, though it is not accepted by all surgeons and is used alongside the other tests rather than in place of them. The strength of a specific thumb muscle, supplied by the median nerve, is also checked, since weakness here supports the diagnosis.
An ultrasound scan is often carried out during the consultation. This is not usually needed to make the diagnosis, which is normally already clear from the history and examination. It is instead used to look at the nerve itself, and to check whether the anatomy of the tunnel is suitable for a smaller-incision technique, or whether the tunnel is too scarred or narrow for anything other than an open operation. Which technique suits which patient is covered in a separate article.
Three things determine this decision. The first is duration of symptoms. Anyone with a short history, under six weeks, who has not yet tried non-surgical treatment, would normally try non-surgical treatment before surgery is considered.
The second is severity. Symptoms that occur only at night, with no symptoms during the day, are more likely to respond to a night splint or a steroid injection. The third is evidence of nerve damage: wasting of the thumb muscle, or numbness that has become constant rather than coming and going. Either of these points toward surgery, because they suggest the nerve has already been damaged.
Two situations are treated differently. Carpal tunnel syndrome that develops in pregnancy usually settles after the baby is delivered, so surgery is less likely to be recommended during pregnancy. Carpal tunnel syndrome linked to poorly controlled thyroid disease is treated by stabilising thyroid control first, since this can resolve the symptoms without any direct treatment to the wrist.
The splints most patients are given are off-the-shelf splints. In the UK, these tend to hold the wrist extended by about twenty degrees. This is because they are designed for wrist sprains, fractures, and tendonitis. They are multipurpose splints, not made specifically for carpal tunnel syndrome.
A flexed wrist narrows the carpal tunnel. An extended wrist stretches a nerve that is already under pressure. Neither position helps. What is needed is a neutral wrist, held straight. Splints generally only help night-time symptoms. Once a patient also has symptoms during the day, splinting on its own is no longer an effective treatment.
A steroid injection is used for its anti-inflammatory effect. When the nerve becomes compressed, it swells, and the steroid effectively reduces that swelling. Where carpal tunnel syndrome is mild and treated early, an injection can fully resolve symptoms in around one in four patients. This is broadly in line with published data: one study following 100 wrists found that 28% remained symptom-free at six months after a single injection.¹
Symptoms present for a long time before treatment are generally associated with a lower chance of a lasting response to injection.
A single injection is normally the extent of this treatment. If it does not resolve symptoms, a second injection is not usually offered. If the first injection has not worked, a second is unlikely to succeed either. There is little to be gained from prolonging pressure on the nerve when surgery is available and reliable.
Treatment for carpal tunnel syndrome is time-sensitive. The longer the nerve is left untreated, the more likely it becomes that some of the damage turns permanent rather than reversible.
One way to picture this is a hose with water running through it. Step on the hose briefly, and the flow stops, then returns to normal the moment the pressure is lifted. Leave a foot pressed on the same hose for a long time, and a dent can remain even after the pressure is removed. The flow never quite returns to what it was. This is not an exact description of what happens inside a nerve, but it captures the idea.
In a nerve compressed for a long time, some of the nerve's own tissue is gradually replaced by scar tissue. Scar tissue cannot be undone by later treatment. This is why muscle wasting, once it has developed, typically does not fully recover. It is also why long-standing numbness has a real chance of not fully resolving, even after a technically successful operation.
This explains a story many patients arrive with: a friend or relative whose carpal tunnel syndrome never got better, even after treatment. In most cases, the issue was not that treatment failed. The condition had been left untreated for years, often long enough for permanent changes to have already set in. Once that has happened, the aim of treatment shifts from a complete cure to stopping things getting worse. Timing, more than any other factor, determines how completely someone recovers.
Surgery involves dividing the ligament that forms the roof of the tunnel, taking the pressure off the nerve. This can be done as an open operation, or through smaller-incision endoscopic or ultrasound-guided techniques. Which technique suits which patient is covered in a separate article.
The recovery pattern below describes an open operation. For the first 48 hours, the hand is kept in a bandage with the arm in a sling, to reduce swelling. Fingers can be moved, but only for essential tasks: eating, drinking, brushing teeth. After 48 hours the bandage comes off. The wound is then kept covered for a further 8 days, so that for 10 days in total, the wound cannot get wet, and the patient should not lift anything that risks reopening it.
Most patients notice discomfort along the sides of the palm during healing, known as pillar pain. This settles as the divided ligament heals, over about three months, which is also when grip strength returns to normal.
Recovery after endoscopic or ultrasound-guided release is quicker than this. Published data shows patients returning to work roughly six to eight days sooner, and regaining early grip strength faster, after endoscopic release compared with open release.² This is, in practice, the main reason many patients choose one of these techniques over open surgery, and it is covered in full in a separate article.
Return to work depends on the type of work. Desk-based roles are usually manageable from around two weeks, which is also when most patients feel comfortable driving again. Light manual roles, such as packing, are usually manageable from around four weeks, though not yet at full capacity. Heavier manual roles, such as building work, generally need around six weeks, unless light duties are available in the meantime. For all of these, it takes about three months to get back to normal.
Recovery varies between patients. Some notice a rapid, complete improvement from the moment they leave theatre. Others still have some pins-and-needles at three months, and are not yet entirely satisfied. Both are within the normal range. Where recovery is slower or less complete than expected, this is worth a proper reassessment. A separate article covers the common reasons carpal tunnel surgery does not fully resolve symptoms.
"Carpal tunnel syndrome only happens to people who type a lot."
Repetitive keyboard use is popularly blamed, but the published data links carpal tunnel syndrome more consistently with diabetes, an underactive thyroid, rheumatoid arthritis, and a higher body weight than with typing specifically. Any of these can make the tunnel more likely to become tight enough to compress the nerve.
"A wrist splint that bends the wrist back is the right treatment."
Most off-the-shelf splints hold the wrist extended by around twenty degrees, because they are designed for sprains and tendonitis, not carpal tunnel syndrome specifically. An extended wrist stretches a nerve that is already under pressure. What actually helps is a splint that holds the wrist neutral and straight.
"If one steroid injection did not work, a second is worth trying."
If the first injection has not resolved symptoms, a second is unlikely to succeed either. A single injection is normally the extent of this treatment, since there is little to be gained from prolonging pressure on the nerve when surgery is available and reliable.
Can carpal tunnel syndrome go away without surgery?
In mild cases, particularly when caught early, yes. A short history of symptoms, night-only symptoms, and no signs of nerve damage on examination all make a full recovery with splinting or an injection more likely.
Do I need a nerve conduction study to be diagnosed?
Not routinely. Most cases are diagnosed from the pattern of symptoms and a clinical examination alone. A nerve conduction study is reserved for cases where the history and examination do not agree, or where the symptom pattern is unusual.
Is it too late to treat carpal tunnel syndrome if I have had it for years?
Treatment can still relieve pressure on the nerve at any stage. Where nerve damage has already become permanent, a complete recovery of feeling and strength may not be possible. This is why earlier treatment generally gives a better outcome.
Why do my symptoms get worse when I am on my phone or reading?
These activities involve a bent wrist and curled fingers for a sustained period, which narrows the carpal tunnel in the same way sleeping position does overnight.
References:
iiS Health, The Cheshire Hand Clinic, provides consultant-led diagnosis and the full range of treatment options for carpal tunnel syndrome, including on-site nerve testing and ultrasound.
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