Carpal Tunnel Syndrome: What Is It?

What is carpal tunnel syndrome?

My intent for this page is to answer this question quickly and simply.

Hopefully, this will provide you some leverage to take control of your own health and your own symptoms. If you can’t physically be in Denver to see me about your carpal tunnel symptoms, you can at least learn the basics here. (Deep dive here if you want it).

Let’s get you some answers.

It’s all about the median nerve

Carpal tunnel syndrome (CTS for short) is all about nerves.

Nerves are the ‘electrical wires’ of your body. They originate in your brain, travel down your spinal cord, and power your hand. Nerves signal your fingers to close around a mug and transmit the feel of the warm ceramic back to your brain.

FIVE major nerves leave the spinal cord to travel down the arm. THREE of these make it all the way to the fingers. ONE is the median nerve.

This nerve travels down the inside of your forearm (Figure 1), and right before it enters the hand, it has to squeeze through a narrow tunnel known as (you guessed it) the carpal tunnel.

Figure 1 - The median nerve (yellow) travels down the inside of your arm and through the carpal tunnel (gray) to enter the hand.

The carpal tunnel - an arch of wrist bones

A little 3-D imagination will help with understanding this.

Imagine you’re the nerve passing through this tunnel. The floor beneath you and the walls on either side are made up of the bones in your wrist, otherwise known as carpal bones. And the roof of the tunnel is a thick ligament known as the ‘transverse carpal ligament.’

Inside the confines of the tunnel, you are surrounded on all sides by nine glistening white tubular structures known as flexor tendons (these bend your fingers into a fist).

So, to review.

Floor. Walls. Ceiling. Nerve plus nine tendons jamming their way through.

Carpal tunnel syndrome = median nerve compression

Now, if anything compresses the nerve in this tunnel, you get carpal tunnel syndrome.

Here’s how this might occur:

• The walls and floor collapse inward. Have you ever woken up in the fetal position? This is a natural tendency during sleep, and it results in wrist flexion (Figure 2). Even if you don’t wake up like this, you may move in and out of this position in your deep sleep stages. Wrist flexion collapses the wrist bones, resulting in higher pressure within the carpal tunnel [1]. And you guessed it. Median nerve compression.

• The flexor tendons become inflamed. Less common conditions such as rheumatoid arthritis lead to swelling of the nine flexor tendons in the carpal tunnel. And what will that cause? Increased pressure within the carpal tunnel. Median nerve compression.

• The roof thickens. This is the most common cause. The thick ligament that forms the roof of the carpal tunnel naturally thickens with age. The ceiling of the carpal tunnel slowly collapses like some claustrophobic nightmare, decreasing the volume of the carpal tunnel and….median nerve compression.

Figure 2 - When we sleep, our body may naturally curl into this position of wrist flexion, which places high pressures on the median nerve that can result in carpal tunnel syndrome

Carpal tunnel symptoms can be felt in any finger but the “pinky”

If your median nerve is compressed as it goes through the carpal tunnel, you will experience some combination of numbness, tingling (ever hit your funny bone?), burning, or shooting pains in your hand.

Specifically, you will feel these symptoms on the palm side of your thumb, index finger, middle finger, and sometimes part of your ring finger. CTS does NOT involve your pinky finger — that is compression of a different nerve around the elbow.

If severe, CTS can even result in weakness or atrophy of the palm side muscles of your thumb (Figure 3 - if this is you, please run, don’t walk to a hand surgeon).

Figure 3 - The area in red is known as your thenar muscles. If this area has shrunk in the hand where you have carpal tunnel symptoms, please get yourself immediately to a hand surgeon. Your carpal tunnel syndrome could be severe and/or permanent.

More to learn

So that’s it!

Hopefully, you now have a higher-level understanding of the anatomy of CTS.

And if you can’t make it to Denver, Colorado, you can find an even more in-depth article here, learn clues towards diagnosing yourself here, or learn about our recommended treatments for CTS here.

Keep learning.

REFERENCES:

[1]: Gelberman, R. H., Hergenroeder, P. T., Hargens, A. R., Lundborg, G. N., & Akeson, W. H. (1981). The carpal tunnel syndrome. A study of carpal canal pressures. JBJS, 63(3). https://journals.lww.com/jbjsjournal/Fulltext/1981/63030/The_carpal_tunnel_syndrome__A_study_of_carpal.9.aspx