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 pressure.

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:

1. By repeatedly flexing and extending the wrist.
2. By moving the fingers rapidly, causing nerve friction.
3. By external pressure or vibration applied to the palm of the hand.

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 Syndrome?

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.      

Some recommendations

• 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 nerve.
   
• 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 time.
   
• 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 prevent injury.
   
• 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 hands.