Perhaps because it’s poorly understood and not commonly discussed, peripheral neuropathy is sometimes called the “silent disease” 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 may result in decreased muscle movement or changes in organ functioning.
Polyneuropthy versus Mononeuropthy
Most of the disorders dealt with in this book are called “polyneuropathies.” This means that they are multiple and usually (but not always) symmetric, affecting both feet, for example, or both hands, in the same way. A term often used to describe this condition is “distal symmetrical polyneuropathy.” In contrast “mononeuropathy” refers to the injury of a single nerve such as in carpal tunnel syndrome, where only one hand and wrist may be affected, or Bell’s palsy, involving a single nerve to facial muscles.
Other neuropathy classifications are based are based on whether the sensory, motor or autonomic nerve fibers are involved. Damage to sensory fibers, concerned with feeling and touching, results either in abnormal paresthesias (sensations) such as tingling, numbness, electrical shocks, or in outright pain. Damage to motor fibers, which are responsible for voluntary movements such as fist clenching, may result in bodily changes such as muscle weakness or atrophy, or cramps and spasms. Damage to autonomic fibers, which affect involuntary or semi-voluntary functions such as control of internal organs, can cause such changes as decreased ability to sweat, loss in blood pressure (with or without dizziness), constipation, bowel and bladder problems, and sexual dysfunction.