Peripheral Neuropathy Explained
Author: John A. Senneff
Source: Numb Toes and Aching Soles: Coping with Peripheral Neuropathy
Perhaps because it’s poorly understood and not commonly discussed, peripheral neuropathy is sometimes called the “silent disease” (though it has company using this tag!). Yet it affects more people than rheumatoid arthritis-a much better known ailment-with just as severe consequences in its worst form.
To start with, it should be understood PN is not really a disease at all. Rather it’s a complex of disorders in the peripheral nervous system resulting from damage to the nerves’ protective coating or from damage to the nerves themselves.
Our peripheral nervous system is made up of nerve fibers bundled together in nerve trunks. They run from the brain and spinal cord (which make up the central nervous system) to other parts of our body. The fibers are shielded by a coating or membrane called the myelin sheath. Like wires protected by insulation, the coated fibers carry “electrical” impulses from receptors located in internal organs, muscles and skin, back to our brain through our spinal cord. When an injury to our peripheral nerves or their protective coating occurs which interferes with the transmission of impulses from these receptors, one of two things (or sometimes both) occurs depending on the receptors and nerve fibers involved. Either the brain simply acknowledges and registers the abnormal transmission as pain or some other unpleasant sensation, or it prompts a response back to the muscle or organ from which the original impulse emanated. In the latter case the response may result in decreased muscle movement or changes in organ functioning.
Peripheral neuropathy (particularly sensory neuropathy) seems in most cases to initially occur at the extremities of the longest nerves farthest from the spinal cord and brain. Consequently the feet, being at the end of the line, are usually the first to be hit. Frequently the hands are next. Over time the afflication can spread to ankles, legs and arms if the underlying cause is not addressed.
There are said to be more than 100 causes of peripheral neuropathy. Diabetes is considered the most common, at least in the United States.1 It is variously estimated that 30 to 65% of people with diabetes have PN to some degree. In this group it is especially prevalent among those having particular difficulty in controlling their blood glucose levels and/or those having high lipid levels (cholesterol and triglycerides), those over 40 and among smokers.
PN also is said to cause pain for up to one-third of people with AIDS or HIV. In fact it is thought to be the most frequent neurologic disorder associated with HIV infection, typically occurring in the later stages of the disease.
Various toxins and metallic poisons (such as arsenic, lead and mercury), certain chemicals (especially solvents and some insecticides), excessive alcohol intake, vitamin deficiencies (particularly B12) or vitamin excesses (B6), nutritional imbalances, and a number of drugs used to treat HIV infections and AIDS can all cause peripheral neuropathy. It can also result from kidney failure, liver disease, rheumatoid arthritis, abnormal blood proteins, cancer (and even cancer chemotherapy, leukemia and shingles).
Certain repetitive activities such as typing can also be the cause of some neuropathies. Carpal tunnel syndrome is one example. This is a so-called entrapment neuropathy-a condition resulting from a nerve lesion at a point where the nerve is confined to a narrow passageway. Another instance of entrapment neurpathy is where restrictive clothing compresses a nerve called the lateral femoral cutaneous nerve which runs from the groin to the upper thigh.
A tendency toward peripheral neuropathy can also be inherited. A family history of the disorder increases the likelihood.
The publication Bio Medical Frontiers reports that the cause of one-third of all neuropathies is unknown-mine included. These cryptogenic disorders are called “idiopathic”. Some clinicians believe many of these unexplained cases are really genetic in origin.
1A Neurologist up on these matters told me leprosy is the most common cause of PN world wide.