CTS is a serious, painful and disabling
neurological condition caused by damage to the median nerve
which extends through the wrist and into the hand at the
center of the base of the palm. CTS is the most common form
of Repetitive Stress Injury (RSI). RSI affects over 100,000
people a year whose repetitive tasks – such as grasping,
stapling and pressing – place continual stress on parts of
their bodies. Symptoms include numbness, tingling, painful
and burning fingers, weakness of grip and aching hands.
Severe, chronic cases result in permanent and painful
weakness, often requiring surgery.
Facts About Carpal Tunnel Syndrome
CTS can be prevented through avoiding
pressure to the nerve and using protection, conditioning
exercises, rest periods and modifying movement and jobs.
There are two main causes of damage to the median nerve that
lead to CTS:
1. Direct impact, prolonged pressure or
vibration applied to the palm of the hand, as during heavy
machine operation. In addition to direct mechanical damage,
pressure compresses the veins and blocks blood circulation
to the nerve. It also starts a vicious cycle by blocking
lymphatic drainage, which in turn further increases the
2. Extending and flexing the
wrist back and forth rapidly, or moving the fingers extremely
rapidly during activities such as typing which can cause
kinking of the nerve or friction from the rubbing tendons.
What causes Carpal Tunnel Syndrome?
Peripheral nerves can be injured in
several different ways. Obviously, they can be severed by a
cutting injury. Local injury otherwise occurs due to focal
pressure. We would like to refer you to an excellent,
detailed textbook on peripheral nerve injuries by Dawson,
Hallett and Millender (referred to as DHM) (Note- See our
Glossary of some useful terms on our About Us page.)
Experiments in guinea pigs by Gilliatt in
the 1960’s demonstrated demyelization in nerves subject to
pressure. In more severe cases, axonal loss was
demonstrated as well. Denny-Brown and Brenner hypothesized
an ischemic mechanism of injury, but histological studies
show that a high pressure, myelin is physically damaged.
Some informative photomicrographs by the late Dr. Gilliatt
appear on page 11 of the DHM textbook. (I had the pleasure
to work with Drs. Hallett and Gilliatt at the National
Institutes of Health years ago.– A. Robert Spitzer, MD).
According to Dawson, Hallett & Millender,
“Observations support the idea that mechanical factors and
not ischemia are critical in the lesion of chronic
entrapment. The mechanical factor responsible has not been
identified, but it may be chronic low pressure or friction.”
There is also evidence to support ischemia
as an important mechanism, as reviewed in DHM. Studies have
been performed in which catheters have been introduced
directly into the carpal tunnel where the actual pressure in
the tunnel is measured.
The pressure in the carpal tunnel in
individuals having CTS is higher than in normal individuals
(about 30-35 mm HG). This is interesting because the
central venous pressure is about 40 mm. In other words, the
pressure in the veins is about 40 mm. Veins are soft and
collapsible. An external pressure close to 40 mm can easily
collapse the veins and cut off blood flow. Thus, the
critical pressure for developing CTS seems to be about the
same pressure it takes to cut off return of circulation by
the venous system. Lower pressures don’t seem to predispose
to the problem.
In summary, the basic pathophysiology of
CTS is excess pressure. Keeping pressure down on the carpal
tunnel is a logical way to try to prevent this disorder,
based on our knowledge of physiology.
There are three common mechanisms to
injure the median nerve:
The Shock-Tek™ glove addresses this third
mechanism. It reduces the external pressure, impact or
vibration applied to the carpal tunnel and median nerve.
Different jobs and sports require different hand actions,
resulting in different combinations of the above causative
factors. Even if two or three of these factors are present,
the Shock-Tek™ glove will often help, if the external
pressure is a significant part of the overall problem.
However, if the entire problem is finger movement or flexion
and extension of the wrist, the glove would not be expected
to provide much benefit.
- By repeatedly flexing and extending the
- By moving the fingers rapidly, causing nerve friction.
- By external pressure or vibration applied to the palm of
CTS is considered a “Cumulative Trauma
Disorder” (CTD). The development of CTS results from a
summation of one or more factors over time. If the more
precipitating factors are present, the stronger each factor,
and the longer the time of exposure, the more likely one is
to develop the injury. Considered mathematically, this
could be expressed as
CTS = v∑factor dtt
In addition to direct pressure on the
nerve, finger movement, wrist flexion and extension, there
are medical contributory factors, such as diabetes, alcohol
consumption, certain genetic factors and vitamin
deficiencies. The stronger each factor, the more factors
present, and the longer the time they are applied, the more
likely is CTS.
What are the Symptoms of Carpal Tunnel
In most cases of CTS, the symptoms are
fairly stereotypical. The predominant symptoms are numbness
and tingling of the thumb, index and middle finger. These
symptoms may be intermittent. Tingling of the small (5th)
digit is usually not CTS. Pain usually only occurs in late
stage or severe disease. Numbness is much more common than
pain. Because of the tingling, many people who have the
earliest stages of CTS, or have an extremely mild,
reversible nerve injury, mistakenly think they have poor
circulation in the hand. Poor circulation in the hand is a
very rare condition. So, many people without definite CTS
or who haven’t developed it yet, can get relief of symptoms
when using the Shock-Tek™ glove.
Loss of grip strength can develop
particularly due to weakness of the thumb muscles. Some
patients report dropping things from their hand. Sometimes,
this is a false weakness and is due to loss of sensation.
For example, some patients say they drop things from their
hand only if they are not looking at the object (i.e. they
can’t feel it).
Please note! Several other conditions
other than CTS can cause numbness or weakness of the hand,
including conditions such as stroke, MS and spinal cord
injury. If you are not sure about your problem, please see
your doctor. Information at this web site is informational
only, and is not meant to replace proper medical evaluation,
diagnosis and treatment. Use of the Shock-Tek™ glove is not
intended as a substitute for proper medical care. If you
think you have a medical problem affecting the hand, please
see your doctor.
Preventing Carpal Tunnel Syndrome
Forceful gripping and repetitive hand and
wrist movements over prolonged periods of time can lead to a
variety of wrist and hand problems, including CTS. Being
aware of the risks and symptoms of CTS and knowing what can
be done to protect the sensitive median nerve area can help
prevent this condition.
- Avoid pressure on the median nerve.
Damage to the median nerve causes CTS. The median nerve
crosses through the wrist and enters the hand at the center
of the base of the palm, carrying sensation from the hand to
the central nervous system. Extended or repetitive
pressure, particularly over the unprotected median nerve
area, can lead to CTS and cause permanent damage to the
- Avoid extended flexing of the wrist.
Whenever possible, keep the wrist straight, and avoid using
it in a bent or twisted position over prolonged periods of
- Grip with the whole hand. Use the entire
hand when grasping objects. Grasping with just the thumb,
index and middle fingers, increases pressure on the wrist.
- Minimize repetitive motions. Any
repeated motion of the hands can strain the median nerve,
causing CTS. Continuous, rapid movement of the fingers or
wrists – as when typing – can cause kinking of the median
nerve or friction from the rubbing of tendons. Prolonged
gripping and other forms of pressure on the nerve can also
cause CTS. When you use tools or equipment of any kind,
vary your technique, grip and position. Avoid holding an
object the same way for a long period of time.
- Rest your hands. Rest and stretch your
hands if they become tired. Alternating tasks, rotating
work activities or regularly switching hands will help
- Minimize speed and pressure.
Forceful repeated movements can put extra stress on the
sensitive wrist area. In some cases, power tools
can reduce the work but they need to be used with
caution, since extreme vibration can also introduce CTS.
No matter what the task, pause to consider how tools
might be used most safely.
- Ask your doctor about conditioning
exercises. Certain exercises can strengthen the hands and
arm muscles to help avoid pressure or strain on the wrists.
NOTE: The above suggestions are not meant
to take the place of a physician’s care and may not prevent
all of the different medical problems that can affect the