In usual cases of polyneuropathy it is the longest nerve-fibers that are most at risk, while the shorter nerve-fibers are less affected. In brief, polyneuropathy is a “length-dependent” neuropathy. Because the longest nerve-fibers in the body are those that run from the lower back to the feet, in typical cases of polyneuropathy the first part of the body to become numb or weak is the feet.
When this occurs, the problem is called a “mononeuropathy,” meaning that a single peripheral nerve is affected. Examples of mononeuropathy include carpal tunnel syndrome in which the median nerve is pinched at the wrist, and peroneal neuropathy in which the peroneal nerve is injured near the knee.
In carpal tunnel syndrome, certain muscles of the thumb can become weak, while numbness affects the thumb, index finger, middle finger and part of the ring finger– but not the little finger. In peroneal neuropathy muscles that lift the front and outer edges of the foot can become weak, while numbness affects the outer surface of the calf and the top of the foot– but not its bottom. In cases of mononeuropathy only the structures connected to that one nerve’s fibers are affected.
The peripheral nerves are bundles containing many individual nerve-fibers, and are similar to telephone cables carrying many individual wires. There are two basic types of nerve-fibers– motor and sensory.
In polyneuropathy muscles ordinarily served by more than one peripheral nerve can become weak, and the numbness extends beyond the territory of any single nerve. He or she could cover the parts of the legs affected by weakness and numbness if a person with polyneuropathy pulled on stockings. Thus, the weakness and numbness affecting the legs are described as showing a “stocking” pattern of loss.
Guillain-Barré syndrome involves inflammation of nerve-roots and nerves (spinal cord connections) caused by an overactive immune system. This is a so-called auto-immune disease in which a person’s immune system attacks a tissue within their own bodies, in this case the nerves. Certain treatments that temporarily suppress the action of the immune system have been shown by randomized, controlled trials– the gold-standard of medical proof– to improve outcome in this condition.
Inherited polyneuropathy can be transmitted in families in either a recessive or dominant form. In families with dominant transmission a bad gene from just one parent is sufficient to produce the disease in a child. In families with recessive transmission defective genes from both parents are required in order to produce the disease.
Diabetes is the most common cause of polyneuropathy in both the U.S. and the rest of the world. One person with severe, long-term elevations of blood sugars might have very little polyneuropathy, while another person might have polyneuropathy as the very first symptom of their diabetes.
Polyneuropathy is more of a category of nerve impairment than a final diagnosis, and numerous diseases can produce the same end-result of stocking-glove loss.
Abstinence can keep the polyneuropathy from worsening, but the already damaged nerve-fibers might not fully recover. Because people with alcoholic polyneuropathy often lack sufficient quantities of thiamine, a vitamin important to the nerves, supplementing well-rounded, nutritious meals with this vitamin is usually helpful.
Medical doctors are usually able to detect polyneuropathy from patients’ histories of symptoms and their physical examinations, but tests of muscle and nerve electricity– called electromyography and nerve conduction studies– are often helpful in characterizing the extent and pattern of nerve impairment.
In contrast, “polyneuropathy” produces a pattern of weakness and numbness completely different from that seen in mononeuropathies. Instead of affecting the fibers of just a single peripheral nerve, polyneuropathy simultaneously impacts fibers traveling in numerous peripheral nerves.
In usual cases of polyneuropathy it is the longest nerve-fibers that are most at risk, while the shorter nerve-fibers are less affected. In polyneuropathy muscles ordinarily served by more than one peripheral nerve can become weak, and the numbness extends beyond the territory of any single nerve. When the medical condition responsible for the polyneuropathy causes worsening damage to the peripheral nerves, the stockings climb ever higher as the next-longest nerve-fibers become involved. One person with severe, long-term elevations of blood sugars might have very little polyneuropathy, while another person might have polyneuropathy as the very first symptom of their diabetes. Because people with alcoholic polyneuropathy often lack sufficient quantities of thiamine, a vitamin important to the nerves, supplementing well-rounded, nutritious meals with this vitamin is usually helpful.
As a final illustration of the range of disease processes that can cause polyneuropathy let’s consider Guillain-Barré (pronounced GEE-on bah-RAY) syndrome, also known by the more cumbersome term of acute inflammatory demyelinating polyradiculoneuropathy. In contrast to the diabetic, genetic and alcoholic forms of polyneuropathy that typically worsen at a pace measured in years or months, Guillain-Barré develops in a matter of days.
When the medical condition responsible for the polyneuropathy causes worsening damage to the peripheral nerves, the stockings climb ever higher as the next-longest nerve-fibers become involved. By the time a person’s stockings climb as high the knees, he or she might also notice symptoms in the fingers. Because the nerve-fibers running from the neck to the fingers are about as long as those running from the lower back to the knees, this is.
He or she could cover the parts of the arms affected by weakness and numbness if a person with polyneuropathy affecting the arms and hands pulled on gloves. Thus, the weakness and numbness affecting the arms are described as showing a “glove” pattern of loss, and when arms and legs are simultaneously impacted, it is called a “stocking-glove” pattern.
