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Diabetes and physical injury (trauma), such as automobile accidents, falls, and medical procedures, are the most common causes of neuropathy.
Neuropathy may affect a single nerve (mononeuropathy) or multiple nerves at the same time (polyneuropathy).
Diabetes is the main cause of polyneuropathy in the United States.
- It is more common in people with long-standing or uncontrolled diabetes.
- About 70 percent of people with diabetes have some form of damage to the sensory (nerves that carry sensations such as pain and touch), motor (nerves that control movements), and autonomic nerves (nerves that control important functions beyond your conscious control such as digestion and heart rate).
Physical injury (trauma) is the most common cause of acquired mononeuropathy. Causes include automobile accidents, falls, and medical procedures that may inadvertently damage the nerves.
13 other causes of neuropathy
- Vascular disorders: Hypertension and peripheral vascular disease can compromise the blood supply to the nerves, causing patchy nerve damage (which is also called multifocal mononeuropathy). Long-standing diabetes, smoking, and atherosclerosis often accelerate neuropathy caused by vascular disorders.
- Nutritional deficiencies: Deficiency of vitamin B complex and folic acid can often precipitate neuropathy. Such deficiencies are often due to extreme dieting or fasting, eating unhealthy food, restrictive diet (vegan diet), gastric bypass surgery, malabsorption syndrome, or alcoholism.
- Medications: Drugs used for cancer treatment, colchicine, antimicrobials, and antituberculosis drugs (isoniazid) may trigger neuropathy due to their toxic nature. Such neuropathy may be irreversible.
- Autoimmune diseases: In some individuals, the immune system of the body attacks its own body's tissues due to immune dysregulation. This dysregulation may be genetic or triggered by an unknown environmental factor. Such diseases are called autoimmune diseases and can either directly target nerves or attack the surrounding tissues causing compression of the nerves. These include systemic lupus erythematosus, Sjogren’s syndrome, and rheumatoid arthritis, among others.
- Multiple sclerosis (MS): MS is a systemic disease with multiple etiology. MS damages the protective covering over the nerves, called the myelin, and causes symptoms such as pain and extreme shock-like sensations over the nerves. Neuropathy affects roughly one-fourth of people with MS.
- Trauma: Physical trauma such as bone fracture, spinal compression, or tumors growing over or near the bone may cause nerve impingement and neuropathy.
- Heavy metal poisoning: Heavy metal toxicity due to lead, arsenic, and mercury may cause direct damage to the nerves, resulting in neuropathy of varying severity.
- Hormonal imbalances: Hypothyroidism, hypercortisolism, and hyperparathyroidism disturb normal metabolic processes, leading to swollen tissues and neuropathies.
- Kidney and liver failure: These often cause nerve damage due to the accumulation of toxins in the body that can damage the nerve tissue. Many people with chronic kidney disease develop varying levels of polyneuropathy.
- Chemotherapy drugs, radiotherapy drugs, and many immunosuppressants: These can cause polyneuropathy in around 40 percent of users. Chemotherapy-induced peripheral neuropathy may be seen in people who are susceptible to it. Symptoms often continue for months after stopping the chemotherapy.
- Cancer-induced neuropathy: Certain types of cancer and benign tumors cause neuropathy in various ways.
- Entrapment neuropathy: Tumor sometimes grows to infiltrate or press on nerve fibers
- Paraneoplastic syndrome: Often seen in many types of cancer, is triggered by a person's immune system response to cancer and can indirectly cause widespread nerve damage.
- Infections: Infections due to herpes zoster, West Nile virus, and cytomegalovirus can attack nerve tissues and cause neuropathy. Lyme disease, human immunodeficiency virus that causes acquired immunodeficiency syndrome, and leprosy can affect the nerves.
- Genetic mutations: These can cause polyneuropathies although these are rare. Genetic mutations can either be inherited or arise de novo (new mutation). An example of inherited neuropathy is Charcot-Marie-Tooth disease, also known as hereditary motor and sensory neuropathy.
What is neuropathy and what are the symptoms?
Neuropathy (or peripheral neuropathy) refers to nerve conditions that involve damage to the peripheral nervous system. The peripheral nervous system consists of all the nerves that lie outside the central nervous system (CNS) and its role is to connect the CNS (brain and spinal cord) to other organs and tissues.
Symptoms of neuropathy include:
- Numbness
- Tingling
- Burning sensation in the affected area (when sensory nerves are affected) or weakness in the body part
- Muscle wasting
- An inability to lift the body part (when motor nerves are affected)
Is neuropathy curable?
Many acquired neuropathies, if detected in early stages, can be cured especially if the trigger or underlying cause is treated. This includes neuropathies due to impingement (trauma or tumor compression), nutritional deficiencies, certain drugs, and to some extent infectious neuropathies.
Management of blood sugars, blood pressure, and lipid levels, and lifestyle modifications, such as quitting smoking, alcohol, regular exercise, weight reduction, and medications, can help prevent the worsening of neuropathy in many cases.
How is neuropathy managed?
Tests performed to diagnose neuropathy include:
- Blood tests: Tests for complete blood count, kidney function, liver function, blood sugars, vitamin B12 levels, folic acid, cholesterol, antinuclear antibodies, rheumatoid factor, and heavy metal levels
- Scans: Radiological investigations such as computed tomography and magnetic resonance imaging for the spine (to detect compression) and tumors may be performed in case of suspected trauma/bone fractures
- Nerve conduction studies: Electromyography and nerve conduction velocity tests may be performed to find out which nerve is affected and the nerve fibers that are involved (sensory or motor neuropathy)
Once the cause of neuropathy is detected, medications can be started.
- Medicines: They are primarily used to control pain due to neuropathy and manage symptoms of abnormal sensations and include:
- Antidepressants such as Duloxetine or nortriptyline
- Antiseizure medicines such as Neurontin® and Gralise® (gabapentin) and Lyrica® (pregabalin)
- Vitamin B12 and folic acid supplements and omega fatty acid supplements
- Topical patches and creams containing Lidoderm® and Xylocaine® (lidocaine) or Capsin® and Zostrix® (capsaicin)
- Physical therapy: It uses a combination of active and passive movements, regular exercise, massages, and other treatments to help you increase your strength, balance, and range of motion.
- Mechanical aids: Braces and specially designed shoes, casts, and splints can help reduce pain by providing support or keeping the affected nerves in proper alignment.
- Surgery: It is the best option for compression-related neuropathy due to spinal disc prolapse, adhesions, tenosynovitis, trauma, and fractures.
- Transcutaneous electrical nerve stimulation: This treatment involves placing electrodes on the skin at or near the nerves that cause your pain. Gentle, low-level electrical current is delivered through the electrodes to your skin in pulses. It often relieves pain and tingling associated with sensory neuropathy.
- Immune suppressing or immune-modulating treatments: These are used for individuals whose neuropathy is due to an autoimmune disease. The goal of these therapies is to stop the immune system from attacking the nerves.
- Complementary treatments: Acupuncture, massage, alpha-lipoic acid supplements, behavioral therapy, and psychotherapy are other methods that may help relieve neuropathic pain.