Heat is not the treatment for carpal tunnel syndrome, and for some people it makes the night symptoms worse. That’s an uncomfortable thing for a company selling heat pads to say, so here it is early.
Heat has a narrow, real use here: loosening a stiff hand and forearm before exercises or work. It does nothing for the nerve compression causing the problem.
What carpal tunnel actually is
The median nerve runs into your hand through a tunnel at the wrist, alongside the tendons that bend your fingers. The roof of that tunnel is a stiff ligament. When the space inside gets tight, the nerve gets squeezed.
That’s why the symptoms have such a specific pattern:
- Numbness and tingling in the thumb, index, middle and half the ring finger. The little finger is spared, because a different nerve supplies it.
- Worst at night. People wake and shake the hand out.
- Worse when holding a phone, a steering wheel or a book. See thumb and wrist pain from phone use.
- Later on, dropping things, and a flattening of the muscle at the base of the thumb.
Numbness in the little finger, or pain in the neck and down the arm, points elsewhere: see neck pain, tech neck and handlebar pressure in cyclists. Get it assessed rather than assuming.
Why heat isn’t the answer
The tunnel is a fixed space with a nerve in it.
Warming the area increases blood flow to the tissues inside a space that has no room to spare, which is the opposite of what a compressed nerve needs. Some people find their night tingling is worse after a warm bath or a hot shower for exactly this reason.
Nor does warmth reach the problem. Heat from a pad penetrates a centimetre or two. The median nerve sits under the tendons, and the ligament over it doesn’t soften in twenty minutes. Heat is equally powerless against the nerve pain of sciatica, for the same reason.
Where heat does have a place
- Before exercises. A warm forearm and hand move more easily, so nerve glides and tendon glides feel less stiff. See “my physio said use heat”.
- When arthritis sits alongside it. Plenty of people have both. Heat helps the stiff arthritic joints in the morning even though it does nothing for the nerve. See hand arthritis and morning stiffness, and trigger finger, which often turns up in the same hand.
- For a tight forearm after a long day of gripping tools, a keyboard or a steering wheel. See tennis and golfer’s elbow.
Keep it to the forearm and the back of the hand, on the lowest setting, for 10 to 15 minutes, then do your exercises. If the tingling is worse afterwards, stop using heat on it. And if sensation in the hand is already reduced, keep heat off it entirely: who should not use a heating pad.
What actually helps
A night splint. This is the first thing worth trying. It holds the wrist straight while you sleep, which is when most people bend the wrist under themselves and squash the nerve. It’s cheap, it’s not invasive, and for mild to moderate cases it often settles the night symptoms within a few weeks.
Changing what provokes it. Sustained gripping, vibration, a bent wrist at the keyboard, long phone calls held in one hand. See upper back pain from desk work for the desk setup.
Nerve and tendon glides, from a hand therapist who has watched you do them.
A steroid injection, which often gives real relief for a period and helps confirm the diagnosis.
Surgery, where the ligament over the tunnel is released. It’s a small operation with good results in the right patients, and it’s the answer when the numbness is constant or the thumb muscle is wasting. Afterwards: heat after surgery and getting a stiff wrist moving again.
Carpal tunnel is also more common in pregnancy and often settles after the birth; see heat during pregnancy and new parent aches. In rheumatoid arthritis and diabetes it’s more common again, and in diabetes the heat cautions are stricter.
Don’t wait it out if…
- The numbness is there all the time rather than coming and going
- You’re dropping things, or struggling with buttons and keys
- The muscle at the base of your thumb looks flatter than the other side
- Symptoms started after a fall or a wrist injury
A nerve under long-term pressure can be slow to recover, and muscle wasting doesn’t always come back. That’s the reason not to spend six months on a heat pad instead.
Related: thumb and wrist pain from phone use and a stiff wrist after a cast.
The heat pad we use
We’ve supplied the Bremed BD7800 since 2010. It holds a steady temperature, covers a whole lower back and has a machine-washable cotton cover. Physiotherapy clinics in Singapore use it with their patients.
Clinically reviewed by: Nigel Chua (Hand Occupational Therapist) & Louise Yow (Physiotherapist). This article is general information, not a diagnosis. electricheatpad.com sells electric heat pads.
