What is Carpal Tunnel Syndrome and how is it caused

Featuring Dr. Bertrand Perey, MD, Orthopaedics

Duration: 3 minutes, 55 seconds

Carpal tunnel syndrome is compression of a nerve at the level of the wrist. The nerve in question is a median nerve, and the tunnel in the wrist is the carpal tunnel.

We have a prop here to help illustrate this. If you see, right here, the yellow lines are in fact branches of the nerve – the median nerve. That nerve gives feeling to the thumb, the index, the long finger, and half of the ring finger. The carpal tunnel is covered by a ligament called a transverse retinacular ligament, which is this white structure here.

So as people get compression in this tunnel the nerve gets affected, and that’s how it affects the fingers. If you don’t have numbness in your hand, you most likely do not have carpal tunnel syndrome.

Furthermore, it’s the pattern of numbness that makes it so special. You have numbness usually at night time or in the morning, so as these nine tendons swell at nighttime, they cause compression on the nerve, causing it to go to sleep.

Patients usually awake at night feeling their hand is dead, like they slept on their hand, that’s probably carpal tunnel syndrome. So after they wake up and move their fingers, thus pushing the fluid out of the tendons, the numbness usually goes away.

Furthermore, some patients sleep with their wrist bent at nighttime. If they sleep with their wrist bent at nighttime it further compresses the tunnel, and this is why in early parts of treatment we can put braces on patients at nighttime to prevent them from doing that.

As the problem evolves people often get numbness in the daytime, blow drying their hair, driving their car, whenever the hand is in the position that's anything but straight, if the wrist is bent or extended, it further compresses the tunnel, causing these symptoms.

And furthermore, as it becomes more and more advanced, patients can get symptoms of numbness doing virtually any task of the day. There's often associated symptoms of pain. Pain is usually felt in the palm of the hand and the forearm, with occasional radiation up to the shoulder.

Most patients who have carpal tunnel syndrome don't have an identifiable cause, so we call it idiopathic. What does that mean? Well, you're born. You're born with a small tunnel, compared to the size of your tendons. And interesting, as you age, the tendons get bigger. So as you go from the age of 15, 16, until the day you die, your tendons are swelling.

So somewhere along that line, if you have a small tunnel, you will develop carpal tunnel syndrome. So if you have a small tunnel, you might get it when you're 30, if you have a bigger tunnel you might get it when you're 45, and if your tunnel's big enough you may never get it. But if we all lived long enough, we may well all get carpal tunnel syndrome. Now that accounts for the vast majority of patients.

There are things, however, that can accelerate the onset of symptoms. One thing would be activities involving a lot of heavy gripping or vibrating tools. The biggest misconception is carpal tunnel is not due to repetitive use of your fingers such as when data entry or typing. It is not due to that at all, that is a completely false understanding of the problem.

There are some other metabolic or medical conditions that can lead to that. One is hypothyroidism. The other one is inflammation of your tendons from something like rheumatoid arthritis. And this your doctor can rule out these elements fairly simply. For the majority of patients there's no defined cause for your carpal tunnel syndrome, other than being born with a small carpal canal.

If you think that you have carpal tunnel syndrome based on the profile of symptoms that you're experiencing, you should contact your family doctor to confirm the diagnosis.

Presenter: Dr. Bertrand Perey, Orthopaedic Surgeon, New Westminster, BC

Local Practitioners: Orthopaedic Surgeon