Carpal Tunnel
The median nerve runs into the hand to supply sensation to the thumb, index
finger, long finger, and half of the ring finger. The nerve also supplies
a branch to the muscles of the thumb, the thenar muscles.
One of the first symptoms of carpal tunnel syndrome is numbness in the distribution
of the median Nerve. This may be quickly followed by pain in the same distribution.
The pain may also radiate up the arm to the shoulder, and sometimes the
neck. If the condition is allowed to progress, weakness of the thenar muscles
may occur. This results in an inability to bring the thumb into opposition
with the other fingers and hinders one's grasp.
Looking at a cross section of the wrist allows one to visualize the anatomy
of the carpal tunnel. The carpal tunnel is an opening into the hand that
is made up of the bones of the wrist on the bottom and the transverse carpal
ligament on the top. Through this opening, the median nerve and the flexor
tendons run into the hand. The median nerve lies just under the transverse
carpal ligament. The flexor tendons allow us to move the hand, such as when
we grasp objects.
The Tendons are covered by a sheet called tenosynovium. The tenosynovium
is very slippery, and allows the tendons to glide against each other as
the hand is used to grasp objects. Any condition which causes irritation
or inflammation of the tendons can result in swelling and thickening of
the tenosynovium. As all of the tendons begin to swell and thicken, the
pressure begins to increase in the carpal tunnel because the bones and ligaments
that make up the tunnel are not able to stretch in response to the swelling.
Increased pressure in the carpal tunnel begins to squeeze the median nerve
against the transverse carpal ligament. Eventually, the pressure reaches
a point when the nerve can no longer function normally. Pain and numbness
in the hand begins.
There are many conditions which can result in irritation and inflammation
of the tenosynovium, and eventually cause carpal tunnel syndrome. Different
types of arthritis can cause inflammation of the tenosynovium directly.
A fracture of the wrist bones may later cause carpal tunnel syndrome if
the healed fragments result in abnormal irritation on the flexor tendons.
The Key Concept to remember is that anything which causes abnormal pressure
on the Median Nerve will result in the symptoms of pain, numbness and weakness
of carpal tunnel syndrome.
Evaluation begins by obtaining a history of the problem, followed by a thorough
physical examination. Description of the symptoms and the physical examination
are the most important parts in the diagnosis of carpal tunnel syndrome.
Commonly, patients will complain first of waking in the middle of the night
with pain and a feeling that the whole hand is asleep. Careful investigation
usually shows that the little finger is unaffected. This can be a key piece
of information to make the diagnosis. Other complaints include numbness
while using the hand for gripping activities, such as sweeping, hammering,
or driving.
The major physical findings reflect that pressure is increased in the carpal
tunnel. If more information is needed to make the diagnosis, electrical
studies of the nerves in the wrist may be requested. Several tests are available
to see how well the median nerve is functioning, including the nerve conduction
velocity and electromyography (EMG). This test measures how fast nerve impulses
are conducted through the nerve.
In the early stages of Carpal Tunnel syndrome, a splint will sometimes decrease
the symptoms, especially the numbness and pain occurring at night. It may
also help control the swelling of the tenosynovium and reduce the symptoms
of carpal tunnel syndrome. If this fails to control your symptoms a cortisone
injection into the carpal tunnel may be suggested. This medication will
decrease the swelling of the tenosynovium and may give temporary relief
of symptoms. If all of the previous treatment fail to control the symptoms
of carpal tunnel syndrome, surgery will be required to reduce the pressure
on the median nerve.
