Hand: Carpal tunnel syndrome

Carpal tunnel is one of the most common hand problems, with one of the simplest treatments. Yet, not everything about it is simple.

  1. Not every hand pain is "carpal tunnel syndrome."
  2. Not every burning in the hand is "carpal tunnel syndrome."
  3. Nobody really knows why some people are prone to getting carpal tunnel syndrome.
  4. It used to be said that carpal tunnel syndrome was caused by "repetitive" hand work. As best we can tell today (2014) repetitive work, such as typing, is not the cause of the problem. Carpal tunnel syndrome is probably a function of genetics.

Understanding the problem

Carpal tunnel syndrome is the most commonly diagnosed upper extremity nerve compression. Other terms for this diagnostic entity include "median mononeuritis," "median neuropathy," or most clearly "median nerve compression at the wrist."

Glossary

The carpal tunnel is a tunnel made of bones and tight fascia, which contains the median nerve and 9 hand tendons. The median nerve is one of the three nerves that reach the hand, the other ones being the ulnar, and the radial nerve. Neuropathy translated into English means quite simply "nerve problem".

Patients typically present with pain, numbness, tingling, burning in the palm of the hand extending to the thumb, index, long, and possibly to the ring finger. As suggested from the previous paragraph, these symptoms results from increased pressure on the median nerve at the carpal tunnel.

Following is a sketch of a carpal tunnel of a cut right hand. To understand the picture imagine somebody's right hand, cut cleanly across at the wrist. This is what it would look like.

The carpal tunnel is the oval that I've colored green. It is surrounded by the carpal bones on 3 sides (brown). The roof of the tunnel, on the palm side, consists of the flexor retinaculum layer.

The contents of the carpal tunnel are the median nerve (colored yellow) and 9 of flexor tendons of the hand (colored blue).

The problem with the carpal tunnel is that it does not expand much, because it is made of bones and a very tight roof that does not give at all. The space available for its contents is fixed. If the tendons get inflamed or swollen for any reason, the space available for the median nerve decreases. A compressed nerve, any compressed nerve, causes pain, tingling, burning, etc.

The typical pain of the carpal tunnel is felt in the palm of the hand, often with burning, tingling, numbness, especially at night.

The area of typical carpal tunnel symptoms is the area that is supplied by the median nerve. The area affected is illustrated in the following diagram.

What else can it be besides carpal tunnel syndrome?

If your symptoms are in the small finger, it is probably not a simple carpal tunnel problem.

If your pain and burning is on the side of the forearm, or in the shoulder, again it is not a simple case of carpal tunnel syndrome.

Other things to consider include diabetic neuropathy, arthritis with compression of one or more nerves at the neck, etc.

What are the treatment options?

  1. Decrease the volume of the tendons
    1. Rest
    2. Splinting. A good wrist splint helps wrest your tendons and should be worn at night. Unfortunately, typical commercially available wrist splints tend to hold the wrist in 30 degrees of extension and don't help. The splint should hold the wrist in neutral alignment, not flexed, not extended.
    3. Injection of corticosteroids provides at least temporary relief. If nothing else, even if relief is temporary, it is a sign that surgery will be successful. Usually, after injection, symptoms recur within a year in most patients.
    4. Physical therapy: nerve and tendon gliding exercises have been shown in at least one study to decrease surgery rates for the first year of treatment
  2. Increase the space of the carpal tunnel through surgery: the operative intervention consists in cutting the roof of the carpal tunnel, thus enlarging the space available for the median nerve.

What is the best treatment?

With accurate diagnosis, open carpal tunnel release is simple and predictable treatment. It can be done with local anesthesia, without general anesthesia, with the patient fully awake. The goal of the surgery is to divide (cut) the roof of the carpal tunnel, which allows the carpal tunnel to become larger.

What is endoscopic carpal tunnel release?

For uncomplicated cases of carpal tunnel that need surgery, in patients who wish to have a very small incision, I perform the endoscopic release described by Agee.

The surgical incision is 1/2 to 3/4 of an inch, sutures are dissolvable, and patients are allowed to start using the hand immediately for low stress activities.

Here are a couple of pictures from an operation:

This is the camera-knife instrument, inserted on the ulnar side of the carpal tunnel of one of my patients.

A view of the flexor retinaculum from inside the carpal tunnel.

After the release roof is cut, fat is seen falling into the cut transverse carpal ligament, verifying complete release.

This is the scar appearance about 2 weeks later.

What are the risks of surgery?

If the surgery is done with general anesthesia, all risks of general anesthesia apply, including the very rare death from anesthesia.

Risks specific to carpal tunnel surgical release include the following and others:

  1. It is possible to damage the very same median nerve that one is trying to free up.
  2. It is possible to perform incomplete release, resulting in continuation of symptoms.
  3. Cutting the palmar cutaneous branch of the median nerve could cause a very annoying numbness right over the carpal tunnel skin.
  4. Infection after carpal tunnel is rare, but it is possible.
  5. Damage to the motor branch of the median nerve is possible as well, and the surgeon stays on the ulnar side of the tunnel in order to avoid this problem.
  6. There is always some bleeding under the skin at the surgery site, and a small bruise will be seen even weeks later.

Why doesn't every surgeon do this surgery with an endoscope?

For severe cases of compression of the carpal tunnel, for the patients who need this surgery most, inserting the endoscope in the carpal tunnel can be difficult and unsafe.

In addition, many hospitals do not own the equipment required.

For multiple reasons, open carpal tunnel release, not the endoscopic method, remains the standard treatment for carpal tunnel syndrome.