ASK DR. BAUGHAN                                                         August 8, 1998

FAULTY WIRING

“Please explain what neuropathies are?”

“Neuro-“ (nerves) “-pathies” (sickness) = sick nerves.  There are many conditions that can cause nerves to not work properly.  In this article, and in general, neuropathies refer to the long nerves that carry signals of sensation or motion, not the nerves that relate to emotions, anxiety or depression.  Some neuropathies are brief and harmless, others can be progressive, permanent and lethal.

Everyone has experienced a neuropathy at some time in their life.  Cross your legs.  Leave them that way and sooner or later, they go numb.  If there is pressure against a nerve, the nerve won’t work very well.  Many people think that if their hands “go to sleep” easily that they have “poor circulation.”  The problem is not in the blood vessels.  The problem is pressure (or stretch) on nerves.  Like our muscles and joints, our nerves lose some elasticity with time, so hands and feet “going to sleep” is more common with age.  If motion and change of position causes the symptom to go away within a few minutes, then no other condition or disease needs to be considered.

Another fairly common harmless but annoying neuropathy has the 25-cent name meralgia paresthetica.  In this condition, the lateral femoral cutaneous nerve is compressed in the waist or groin by a belt, wallet, prolonged sitting, tight pants, or adiposity (a 25-cent word for fat).  This nerve carries the sensation from the outside of the thigh.  The person usually complains of numbness or tingling on that part of the thigh, as though it were trying to wake up but couldn’t.  The condition may persist for months, but it does not mean other parts of the nervous system are going to malfunction.

Carpal tunnel syndrome is a condition in which the median nerve to the middle fingers of the hand is compressed by the tendons that bend the fingers as they go through the narrow arch of wrist bones (the carpal bones).  Since this nerve carries motion signals as well as pain signals, prolonged pressure is not only painful, but can compromise the strength and use of the hand.  Treatment with splints or medicines attempts to reduce swelling of the tendons and tissues compressing the soft nerve.  Surgical treatment releases the pressure by cutting a ligament that connects the two ends of the arch of bones (creating the “tunnel”).

Many other things can cause neuropathies by pressure or stretch.  Herniated discs in the spine, bone spurs, arthritis, scar tissue, trauma or tumors can press on nerves anywhere from their beginning to their end.  The decision on how much testing to do is usually guided by the persistence of pain or the loss of some function.

Nerves respond to many other systems in the body such as the circulatory system or the endocrine (hormonal) system.  Diabetes can cause the nerves in the feet (or eye muscles, or intestines) to malfunction, resulting in pain or numbness.  Numbness can then cause pressure points or sores to develop without the person noticing.  That is why people with diabetes should look at their feet daily to check them.  Thyroid disease can also cause neuropathies with similar symptoms.

Pernicious anemia is a deficiency of vitamin B12 that can cause numbness in a “stocking-glove” distribution.  Other vitamin deficiencies or excesses can also affect nerve function.  Surprisingly, long-standing syphilis can cause symptoms very much the same.  Other infectious diseases such as Lyme disease can show up with neuropathies.

Finally, there are some diseases that cause degeneration of the nerves of unknown cause, such as multiple sclerosis or ALS.  So the evaluation of neuropathies takes a careful history and physical examination and consideration of a broad range of possible causes.  Some are treatable, some are not, so no generalities should be accepted.  But if the symptoms do not cause intolerable pain or loss of function, be reassured that the chance of a serious problem is low.