Carpal Tunnel Syndrome

The term “carpal” is Latin for hand.  Literally interpreted, carpal tunnel syndrome means hand tunnel syndrome.  In terms of causality, the most important word is the middle word – tunnel.  Any tunnel, whether it be a tunnel in the human body, a ground hog tunnel or a tunnel for motor vehicles has a fixed amount of space.  Every tunnel has a limited amount of space.  Therefore, carpal tunnel syndrome is four times more common in women than men.  The reason for this is that, in general, women have smaller hands than men.  Hence, women have smaller hand tunnels than men. For the same reason, the #1 risk factor for carpal tunnel syndrome as consistent with our professional medical experience and training, as well as the scientific medical literature, particularly in the past 25 years, is obesity.  It is quite common for a woman to graduate from high school weighing 120 to 140 pounds.  Years later, women in their 40s and 50s weighing 200 or more pounds, with numbness and tingling in their hands almost always are proven to have developed carpal tunnel syndrome.  The additional adipose and soft tissues deposited in the hand tunnel associated with obesity shrinks the size of the tunnel as the hand bones do not grow beyond puberty to account for the increase in body mass index. In considering the above, the “bread and butter” case for carpal tunnel syndrome is an obese woman in her early 40s of short stature (and therefore small hands). The symptoms of carpal tunnel syndrome include numbness and tingling in all digits of the hand but more often more noticeable in the thumb, index finger and long finger, pain on the palm side of the wrist, an aching pain in the thumb pad and loss of grip strength.  A common additional symptom for carpal tunnel syndrome is hand numbness and tingling waking a person up at nighttime.  This is due to the fact that people fall asleep with their wrist flexed (doubles the carpal pressure) or extended (triples the carpal pressure) which results in deprivation of blood flow to an injured nerve which results in symptoms within the median nerve (carpal tunnel nerve) distribution.

The most common causal factors for carpal tunnel syndrome in our professional medical experience as well as the scientific medical literature include the following:

Obesity

The carpal tunnel is a space-confining issue and the additional adipose and soft tissues deposited within the tunnel compromise the carpal tunnel space and compress the median nerve.

Woman

Women are four times more likely to develop carpal tunnel syndrome than men because they have smaller hands than men which means they have smaller carpal tunnels than men.

“Middle age”

The majority of carpal tunnel syndrome cases occur in individuals in their 40s and 50s with a peak incidence of life in the early 40s.  This is also viewed as many individuals have an elevated body mass index by this time in their life in comparison to their teenage years and 20s.

Hypothyroidism

A low thyroid condition meaning that there is a low metabolism often is associated with weight gain.  An elevated body mass index/obesity is the #1 risk factor for carpal tunnel syndrome.

Diabetes Mellitus

Diabetes most commonly occurs in an obese individual so this may be viewed as another way of saying the same thing, namely that obesity is the #1 cause of carpal tunnel syndrome.  On a separate pathophysiologic basis, diabetes is noted to cause a microvasculitis.  It adversely affects the small blood vessels.  Some of the small blood vessels adversely affected go to the median nerve and contribute to carpal tunnel syndrome.  Diabetics are more prone to developing entrapment neuropathies at the wrist, elbow and knee.

Wrist Fracture

The term carpal tunnel syndrome was coined in the 1938 by an orthopedist, Dr. Moersch, who noted that the hand tunnel dimensions were compromised by a wrist fracture.  He dubbed this carpal tunnel syndrome.

Peripheral Neuropathy

A person with a peripheral nerve disease process, from such entities as diabetes, alcoholism, chemotherapy, vitamin B deficiency, or otherwise, is more predisposed to developing entrapment neuropathies, including but not limited to carpal tunnel syndrome.

Pregnancy

Pregnancy may be viewed as a form of weight gain which is the #1 risk factor for carpal tunnel syndrome.  Even after pregnancy, there is increased risk for carpal tunnel syndrome due to the fact that pre-pregnancy weight is often not achieved.

Rheumatoid Arthritis

Inflammation of the bones at the joint of the wrist can compromise the carpal tunnel space.  Therefore, this form of arthritis which is known for adversely affecting the wrist joint can directly lead to carpal tunnel syndrome.

Hypercholesterolemia

By similar way of the diabetic mechanism of injury, high cholesterol contributes to plaque formation in arteries and arterials which compromises blood supply which eventually can also adversely affect peripheral nerves, including the median nerve, known as the carpal tunnel nerve.

All the above risk factors for carpal tunnel syndrome are considered personal attribute risk factors.  This means that they are medical risk factors that did not involve any type of physical activity, and in such persons, a sedentary state of existence can cause carpal tunnel syndrome.

In terms of physical exertion, frequent, forceful gripping can cause carpal tunnel syndrome.  Exact data is not published.  In the doctors experience, five pounds or more of forceful gripping for 200 or more times per day does place one at significant risk for carpal tunnel syndrome.  The doctors are occasionally asked if weight lifting can cause it.  There is no documentation that weight lifting causes it.  In that scenario, lifting weights to improve one’s physique certainly involves forceful enough gripping but not frequent enough gripping as most often 3 sets of 8 or 10 repetitions for three or four exercises are performed on any given day. Lastly, it is an absolute fallacy that typing causes carpal tunnel syndrome.  Typing does not change the dimension of the carpal tunnel.  The size of the hand tunnel has to do with the anatomy of the person which would include bone structure and soft tissue mass.  There is no study in any peer-reviewed medical journal in any country that demonstrates typing causes or contributes to carpal tunnel syndrome.  Typing is extremely sedentary and it cannot cause an injury. In fact, a study out of the world renowned Mayo Clinic published in the medical journal Muscle and Nerve, studied medical secretaries at their busy institution and compared them to age-matched women and found that there was no increased incidence of carpal tunnel syndrome in Mayo Clinic’s medical secretaries in comparison to age-matched women.  In other words, the factors of age and being a woman were the most important in that study and it has helped prove that typing does not cause carpal tunnel syndrome.  By testing secretaries and transcriptionists over the years, we have noted that only those who are considered morbidly obese by medical definition were the ones who had electrodiagnostically confirmed carpal tunnel syndrome. In terms of diagnosing carpal tunnel syndrome, there are cases in which the clinical examination is normal.  Nerves provide feeling to skin and strength to muscles.  Therefore, it is still imperative to evaluate sensation to light touch as well as thumb abduction strength.  In addition, a square-shaped wrist of 0.7 anterior to posterior and medial to lateral approach or greater is a risk factor for carpal tunnel syndrome.  In simpler terms, if the wrist is thick like the palm of the hand, that person is at increased risk for carpal tunnel syndrome and that is also a sign of carpal tunnel syndrome.  The Phalen maneuver is a reasonable test also.  The Tinel sign is not reliable. The gold standard for the diagnosis of carpal tunnel syndrome is nerve conduction studies.  Nerve conduction studies were developed in the mid 1950s and standardized by the mid 1960s.  Nerve conduction studies are very sensitive and specific for carpal tunnel syndrome and can detect mild cases even when the clinical examination and all imaging studies are normal.  Such testing should be done by a physician trained in neuromuscular anatomy, physiology and pathophysiology with further training in electrodiagnostic medicine, such as physiatry.

Carpal Tunnel Syndrome References