Neuropathy is a generic term that refers to damage to the peripheral nerves that transmit messages from the central nervous system to the muscles, glands and organs, as well as sensory information from the skin and special senses to the brain. When there is injury to a single nerve it is called a mononeuropathy, as seen in carpal tunnel syndrome where the median nerve is compressed by a tendon at the wrist. When it occurs at multiple nerves it is called polyneuropathy. Nerve diseases can be classified as “demyelinating” when they affect the protective layer covering the nerve fibers and help them conduct impulses more quickly, or “axonal” when they involve the nerve fibers (axons) themselves. Sometimes the damage starts at the toes and progresses upward over time. This is the pattern when neuropathy is due to a metabolic disease like diabetes or a vitamin deficiency. Sometimes the injuries are spotty affecting different nerves, as seen with vasculitis. The damage can also be specific to motor nerves that control the muscles, sensory nerves or autonomic nerves.
Sometimes nerve diseases can present suddenly with rapidly progressive weakness due to inflammation, as in the Guillain-Barre syndrome (GBS), which often requires hospitalization and intravenous treatments such as intravenous immunoglobulin (IVIG) which reduces the immune response to the nerves, or plasma exchange in which antibodies are removed from the blood in a “blood-washing” dialysis machine, usually every other day for 5 treatments. Recovery from GBS may take many weeks and require inpatient rehabilitation. GBS is usually a single episode that does not recur, but a variant disease called CIDP can cause fluctuating symptoms of weakness and sensory changes and require long term therapy to suppress the immune response.
There are many causes for neuropathy, including mechanical trauma, toxins, vitamin deficiencies and hereditary genetic diseases like Charcot-Marie-Tooth disease. Diabetes is one of the most common causes of neuropathy, and commonly causes numbness, tingling and pain at the feet. A number of medications, particularly cancer chemotherapy, can cause neuropathy. Your neuromuscular specialist may perform an EMG to determine the location, type and severity of the nerve disorder, and order blood tests to check for diabetes, vitamin deficiencies and other possible causes. Genetic testing may be appropriate if there is a family history of nerve disease.
Medications for neuropathy can help with symptoms such as burning and pain associated with neuropathy, but do not help the weakness or numbness and do not prevent the neuropathy from progressing. Treating the cause of neuropathy, such as improving control of blood sugar for diabetic neuropathy, stopping toxic exposures or vitamin supplements for vitamin-deficient neuropathies can help prevent further nerve damage.