The short answer
Carpal tunnel symptoms peak at night because most people sleep with the wrist bent, which raises pressure inside the tunnel several times over, and because fluid redistributes when lying flat. A neutral wrist splint worn at night is the single most effective conservative measure.
- Night symptoms come from a bent wrist raising pressure in the tunnel, plus fluid shift when lying flat.
- A splint that holds the wrist genuinely neutral is the most effective conservative measure; many off-the-shelf splints hold it extended.
- Little finger involvement points away from the median nerve and toward the neck or the ulnar nerve.
- Constant numbness or thumb muscle wasting is a surgical referral, not a reason to persist with splinting.
- A splint that holds the wrist genuinely straight, worn every night, is the whole of the first six weeks for most people.
Waking at two or three with a numb, burning hand that you have to shake out is the most recognizable presentation in hand medicine.
It is also one of the few where a cheap intervention, correctly applied, resolves a large share of cases.
What the carpal tunnel is
A narrow passage on the palm side of the wrist, floored by the carpal bones and roofed by a thick ligament. Through it run nine tendons and the median nerve.
The space is fixed. Anything that increases the volume of the contents, or reduces the space, raises the pressure on the nerve.
The median nerve supplies sensation to the thumb, index, middle and half the ring finger, and it powers the muscles at the base of the thumb. That distribution is the map that identifies the condition.
Why it is worse at night
Wrist position. Pressure inside the tunnel is lowest with the wrist neutral and rises sharply with flexion or extension. Most people sleep with the wrist curled.
Fluid. Lying flat redistributes fluid toward the upper body, and any swelling in the tunnel raises the pressure further.
Absence of movement. During the day, constant small movements pump fluid through and vary the pressure. Asleep, that stops for hours.
Put together, those explain why the symptom clock is so consistent from patient to patient.
The pattern that identifies it
Numbness or tingling in the thumb, index and middle fingers. The little finger is spared, because it is supplied by the ulnar nerve.
Symptoms that wake you and are relieved by shaking the hand or hanging it over the edge of the bed — the flick sign, which is one of the more useful pieces of history in the whole examination.
Provocation by sustained gripping, driving, holding a phone, or reading a book.
In longer-standing cases, weakness of thumb opposition and visible wasting of the muscle bulk at the base of the thumb. That finding changes the urgency.
The splint, and why it is worn at night
A splint holding the wrist neutral removes the position that raises the pressure. That is the entire mechanism and it works.
Neutral means straight, not extended. Many off-the-shelf splints hold the wrist in twenty or thirty degrees of extension, which is worse than nothing. Check it or have it checked.
Worn every night for six weeks. Most people who respond notice a change within two.
Daytime use is optional and generally reserved for specific provoking tasks, because a wrist immobilized all day gets stiff.
What else helps
Nerve gliding exercises, which move the median nerve through its tunnel rather than stretching it. Done gently, several times a day.
Manual therapy to the carpal bones and the transverse ligament, and to the forearm.
Addressing the neck and the shoulder, because a nerve that is irritated at more than one point along its length is more symptomatic than one irritated at a single site.
And ergonomic changes: keyboard height so the wrists are not extended, a mouse that does not require a bent wrist, and breaks from sustained gripping.
What causes it in the first place
Often nothing identifiable. But several things raise the risk and are worth knowing about.
Pregnancy, because of fluid retention. These frequently resolve after delivery and are worth managing conservatively in the meantime.
Hypothyroidism, diabetes, rheumatoid arthritis, and obesity all increase risk, and the first two in particular are worth excluding in a new case without an obvious mechanical cause.
Repetitive forceful gripping and vibration exposure at work. Keyboard use, despite its reputation, has a weaker association than most people assume.
When it is not the wrist
Cervical radiculopathy at C6 produces numbness in the thumb and index finger and is regularly mistaken for carpal tunnel. The clue is neck movement provoking it, and symptoms above the wrist.
Thoracic outlet syndrome produces a more diffuse pattern, often worse with the arm overhead.
Peripheral neuropathy from diabetes gives a stocking-and-glove pattern in both hands and both feet.
And the double crush phenomenon is real: a nerve compressed at the neck is more vulnerable at the wrist. Some patients need both addressed.
Testing, and what it adds
Nerve conduction studies measure how well the median nerve conducts across the wrist. They are useful for confirming the diagnosis and grading severity.
They are not perfect: a proportion of clinically clear cases test normal, particularly early.
They matter most when surgery is being considered, or when the diagnosis is genuinely unclear.
Ultrasound of the nerve is increasingly used and is quicker and more comfortable.
When to consider surgery
Constant numbness rather than intermittent. That indicates the nerve is affected at rest, not just under provocation.
Any muscle wasting at the base of the thumb, or measurable weakness of thumb opposition. This is the finding that turns a wait-and-see into a referral.
Failure of a properly conducted conservative course — a correctly fitted neutral splint worn nightly for six to twelve weeks, plus the rest of it.
Carpal tunnel release is a short procedure with good outcomes in appropriately selected patients. Where there is genuine nerve compromise, delaying it risks permanent change.
What recovery looks like after surgery
Night symptoms usually resolve quickly, often within days, which is the change people notice first.
Numbness that has been constant for a long time recovers more slowly and sometimes incompletely, which is the argument against waiting too long.
Grip and pinch strength take about three months to return, and scar sensitivity is normal for six to eight weeks.
Rehabilitation is straightforward but not optional: nerve and tendon gliding early, then progressive grip loading.
Pregnancy, and why it is different
Carpal tunnel symptoms in pregnancy are common, usually appear in the third trimester, and are driven by fluid retention rather than by anything mechanical you did.
The large majority resolve within weeks to a few months of delivery, which changes the whole calculation: the aim is comfort until then, not a permanent fix.
Night splinting is the mainstay and it works well. Elevation, and avoiding sustained gripping, help.
Surgery is very rarely appropriate during pregnancy, and it is worth saying so clearly, because the symptoms can be severe enough that people start asking about it.
The habits that quietly keep it going
Sleeping with the hand tucked under the pillow or under the body, which is the most flexed position available and is where most people end up.
Holding a phone or a tablet for long stretches with the wrist bent back.
Driving with a firm grip on the wheel for a long commute, which is a sustained grip with a static wrist for an hour at a time.
Cycling, particularly on drop handlebars, which combines pressure on the palm with wrist extension. Padded gloves and changing hand position frequently both help.
A reasonable order of operations
Get a correctly fitted neutral night splint and wear it every night for six weeks.
Add nerve gliding and sort out the keyboard and mouse.
Have the neck and shoulder assessed, particularly if symptoms extend above the wrist or the splint has not helped.
If there is constant numbness or any thumb weakness at any point, skip ahead and get a surgical opinion rather than persisting.
What to expect week by week
Week one to two: the splint should change the nights. If it does not, check that it is genuinely neutral before concluding it has failed.
Week three to six: daytime symptoms reduce, and the tasks that provoked it become tolerable for longer.
Week six to twelve: symptoms intermittent rather than daily, and grip strength returning.
A case that is unchanged at six weeks of a correctly fitted splint is a case that needs a different answer, not more of the same one.
What I would check at a first visit
The exact distribution of symptoms, mapped on your own hand. Little finger involvement points away from the median nerve.
Thumb opposition strength and the muscle bulk at the base of the thumb, compared side to side.
Provocation tests at the wrist, and a full neck screen including a flexion-rotation assessment.
And your splint, if you have one, because a surprising number of people are wearing one that holds the wrist in exactly the position that causes the problem.
That last check takes ten seconds and it resolves a surprising share of cases that arrive labeled as having failed conservative treatment. Conservative treatment that was never correctly applied has not failed.
