Carpal tunnel syndrome is when the median nerve in the wrist becomes compressed or pinched thereby slowing the electrical nerve impulses across it resulting in numbness and tingling usually in one or more of the following fingers: thumb, index, middle and thumb side (radial side) of the ring finger.

Carpal tunnel syndrome does not cause numbness and tingling in the fifth (pinky) finger nor usually the “pinky side” (ulnar) of the ring finger. The median nerve is the “carpal tunnel nerve.”

There is actually a true tunnel at the base of the wrist that is comprised of the bones of the wrist on the dorsal “back of the hand” side of the wrist and a ligament (the transverse carpal ligament on the palmar (front side) of the wrist. The transverse carpal ligament spans across two bones on either side and within the tunnel pass two tendons for the index, middle, ring and pinky finger and one tendon for the thumb. A total of nine tendons pass through the tunnel in addition to the median nerve.

If, for some reason, swelling occurs within the tunnel as the patient gets older, the ligament gets tighter or arthritic changes in the bones cause narrowing of the tunnel. The carpal tunnel nerve is soft and pliable whereas the tendons are more hard. Therefore, the soft, pliable nerve gets compressed and/or gets a “kink” in it resulting in slowing of the electrical nerve impulses across it which results in the numbness and tingling often associated with carpal tunnel syndrome.

It is analogous to taking a wire and bending it and forming a kink in the wire. The electricity doesn't flow as well through it, and even if you unkink it, it still is not the same.

Very often carpal tunnel syndrome is caused by repetitive-type use - typing, repetitive factory work and anything that causes excessive overuse of the tendons in the forearm, wrist and hand which results in swelling of the tendons and the tendon sheaths.

That swelling and inflammation effectively causes increased pressure and effectively “narrows” the carpal tunnel causing compression of the nerve resulting in the symptoms. Many times by stopping the offending activity the inflammation, swelling, and symptoms will resolve.

Sometimes it requires wearing a splint at night, because when we sleep we often sleep with our wrist bent in a flexed position which causes compression on the nerve. The wrist splint brings the wrist back into a more extended position opening up the canal/carpal tunnel more, taking pressure off the nerve and allowing it to “breathe” more and therefore recover from a day's activities.

This conservative treatment works well in many instances.

However, there are times when even that doesn't work. Cortisone shots have really not been proven to be long-term effective in the carpal tunnel area. Anti-inflammatories by mouth may help a little bit but also are not often curative.

In addition to the numbness and tingling in the radial (thumb side) 3 1/2 fingers in the hand, other ways that the carpal tunnel is diagnosed is by physical exam and neurodiagnostic studies.

On physical exam, usually if we have the patient hold their wrists flexed together for a minute or longer this will often reproduce the symptoms of numbness and tingling. This is called Phalen's sign. Many times, if we tap right on the actual nerve at the wrist area, it is irritated enough that it actually reproduces a numbness and tingling shooting into the fingers. That is called Tinel's sign.

The best objective confirmatory test would be nerve conduction studies. Small needles are placed on either side of the carpal tunnel and electrical impulses are conducted across the nerve. Normal speeds are known, and if the speeds are slowed down due to the compression, carpal tunnel can be objectively diagnosed. If this does not get better with conservative treatment, then surgical treatment is often effective.

The surgery can be done through a small incision on the palmar (front side) of the wrist cutting through the skin, the connective tissue and then the ligament itself. When the ligament is cut, it spreads apart given more “breathing room” and effectively widening the tunnel. The ligament does heal, but it heals in a more spread apart configuration giving more breathing room to the nerve and resolving the symptoms.

Sometimes, just like a kinked wire becoming un-kinked, the nerve cannot completely recover and some symptoms are noted. There are some people who have let it “go too long” who do not get better.

There is also an endoscopic procedure that is done through smaller incisions and can allow for earlier recovery back to work. It is perhaps slightly less effective and slightly more risky, but it is also effective and usually results in less pain immediately post operatively.

There are other slight risks associated with surgery such as bleeding, infection, nerve or blood vessel damage, tendon injury, reaction to medication, medical problems, death, wound problems, blood clots, reflex sympathetic dystropy, etc. but again, all of those are rare.

Dr. Marc P. Pietropaoli is a board certified/fellowship trained orthopedic surgeon/sports medicine specialist.