Carpal Tunnel Syndrome
By: Kendrick E.
Lee, MD
Carpal tunnel
syndrome results from pressure on the median nerve as it passes through a tight
tunnel (the carpal tunnel) in the palm.
The carpal tunnel is enclosed by bone on three sides and a thick fibrous
band on the fourth side. The median
nerve shares the carpal tunnel with the nine flexor tendons which flex the
fingers and the thumb. Any swelling or
unusual structure which takes up space in the tunnel can cause pressure on the
nerve, which decreases the blood flow and nutrition of the nerve. The median nerve gives sensation to the palm
side of the thumb, index, middle and part of the ring finger. The nerve also controls the thenar muscles,
which position the thumb prior to pinch.
The primary symptoms are numbness of
the thumb, index, middle and part of the ring finger, and nighttime awakening
with hand pain and numbness. Pain can
occur, but pain is not the primary symptom of CTS. If pain is the only symptom, carpal tunnel
syndrome is not likely. In
advanced cases there can be weakness or paralysis of the thenar muscles with
loss of dexterity and pinch.
The causes of carpal tunnel syndrome
remain unclear in most cases. Although computer use is popularly thought to
cause carpal tunnel, the association is not proven. Assembly line work with constant repetitive
strong grip has been associated with a higher risk of carpal tunnel
syndrome. Other factors can include
diabetes, kidney dialysis, hypothyroidism, and dozens of other conditions.
The diagnosis of carpal tunnel
syndrome is based on history and clinical examination. X-rays are usually not necessary, except to
rule out other conditions. A nerve
conduction study is an electrical examination of the function of the
nerve. A positive test confirms the
clinical diagnosis. A negative test
does not rule out the diagnosis.
Initial treatment includes activity
modification and night time splinting.
Although popular for pain control, medications likely do not help
much. Stretch exercises may help.
Physical therapy may help by teaching activity modification. A steroid injection given into the carpal
tunnel can reduce swelling in the tunnel and provide relief, often temporary, but
at times long lasting.
If carpal tunnel symptoms persist
and are disabling, surgery can be considered.
Surgery opens the tight fibrous “roof” of the tunnel, decreasing the
pressure and improving the blood flow to the nerve. Surgery takes about 15 to 30 minutes and is done under local,
nerve block or general anesthesia as an outpatient. Immediate finger motion and use is encouraged. Grip weakness and hand soreness with pressure
on the “heel” of the palm can persist for several months, but usually resolve
with time and use of the hand. If no
other hand problems are present, over 90-95 % of surgery patients should have
gratifying, often dramatic relief of the numbness, night awakening, and pain.