Houston Methodist. Leading Medicine

Hand FAQ

Question:

I had carpal tunnel surgery about nine months ago. It's taken me a while to search this but I was told the cause of my problem was an extra tendon in there. Can you tell me more about this? How did I get an extra tendon? Does this happen very often? Will I get carpal tunnel on the other side because of this?

Answer:

Carpal tunnel syndrome (CTS) is a common problem affecting the hand and wrist. Symptoms begin when the median nerve gets squeezed inside the carpal tunnel of the wrist, a medical condition known as nerve entrapment or compressive neuropathy. Any condition that decreases the size of the carpal tunnel or enlarges the tissues inside the tunnel can produce the symptoms of CTS. The most common cause of narrowing in the carpal tunnel is a thickening of the flexor tenosynovium. This is the lining around the tendon that contains fluid to help the tendons slide and glide easily. When the connective tissue gets thick and dried out, the tendon gets stuck and pulls or presses on the nerve. The result can be the characteristic numbness and tingling of the fingers and hand. Unusual anatomy or alterations in the normal anatomy can be another cause of carpal tunnel syndrome. It doesn't happen very often -- estimated at one in 100 cases. There could be a narrow passageway at the wrist because of the shape, structure, or alignment of the carpal bones. There could be a missing protective covering of fascia over the carpal tunnel. Pressure from the contracting muscles and tendons could then compress the nerve more easily. There is also a transverse carpal ligament that crosses over the carpal tunnel. This, too, can become thickened and apply pressure to the nerve. When there is an extra tendon, it usually has something to do with a tendon normally present in about 90 per cent of all humans. That's the palmaris longus tendon. Sometimes this tendon is absent and another tendon is present instead (the palmaris profundus). In some people, both the palmaris longus and the palmaris profundus are present. Pressure from either (or both) of these tendons can cause carpal tunnel syndrome. Only one out of 1600 people have the palmaris profundus muscle. So you can see this particular cause of carpal tunnel is very rare. There have been reports of the palmaris profundus being encased inside the sheath or lining that covers and protects the median nerve. With this abnormal arrangement, any time the muscle/tendon unit contracts, it puts pressure on the nerve. Whether or not this could happen on the other hand is uncertain. There are no studies to document how often this problem occurs bilaterally (on both sides). For a better understanding of your own condition, you can ask the surgeon for a copy of the surgical notes. Reading the details of the procedure may give you a better idea of the exact difference(s) in your anatomy. Or you can just ask the surgeon to give you the particulars of your case at your final follow-up appointment. Ahmed Elbardouni and Moradh Elyaacoubi. Carpal Tunnel Syndrome Caused by a Palmaris Profundus Muscle. In Journal of Orthopaedics. Vol. 8. No. 3. e4.

*Disclaimer:* The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic.
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