Your nervous system is made up of the central nervous system (CNS) and peripheral nervous system (PNS). The brain and spinal cord make up the CNS, whereas the PNS is a series of nerves that run throughout your body.
The PNS is a vast communications network that transmits information from the brain and spinal cord (the central nervous system) to every other part of the body, like muscles, skin and internal organs. Peripheral nerves also send sensory information back to the brain and spinal cord, such as a message that the feet are cold or a finger is burned. Damage to the peripheral nervous system, known as peripheral neuropathy, interferes with these vital connections. Like static on a telephone line, peripheral neuropathy distorts or interrupts messages between the brain and the rest of the body. It can impair muscle movement, prevent normal sensations in the arms and legs, and cause pain.
Types of Peripheral Neuropathy
There are several different kinds of peripheral neuropathies that stem from a variety of causes. They range from carpal tunnel syndrome (a traumatic injury common after chronic repetitive use of the hands and wrists, such as with computer use) to nerve damage linked to diabetes.
As a group, peripheral neuropathies are common, especially among people over the age of 55. All together, the conditions affect 3% to 4% of people in this group.
Neuropathies are typically classified according to the problems they cause or what is at the root of the damage. There also are terms that express how extensively the nerves have been damaged.
Damage to a single peripheral nerve is called mononeuropathy. Physical injury or trauma such as from an accident is the most common cause. Prolonged pressure on a nerve, caused by extended periods of being sedentary (such as sitting in a wheelchair or lying in bed), or continuous, repetitive motions, can trigger mononeuropathy. If the fibrous, shock-absorbing discs that lie between the bones in the back are damaged, they could press on a nerve and cause this type of neuropathy.
Carpal tunnel syndrome is a common type of mononeuropathy. It is called an overuse strain injury, which occurs when the nerve that extends through the wrist is compressed. People whose work requires repeated motions with the wrist extended (such as assembly-line workers, physical laborers, and those who use computer keyboards for prolonged periods) are at greater risk.
The damage to the nerve can result in numbness, tingling, unusual sensations, and pain in the first three fingers on the thumb side of the hand, particularly while sleeping. In time, carpal tunnel injuries can weaken the muscles in the hand. You may also feel pain, tingling, or burning in your arm and shoulder.
Polyneuropathy accounts for the greatest number of peripheral neuropathy cases. It occurs when many peripheral nerves throughout the body malfunction at the same time. Polyneuropathy can have a wide variety of causes, including exposure to certain toxins, poor nutrition (particularly vitamin B deficiency), and complications from diseases such as cancer or kidney failure.
One of the most common forms of chronic polyneuropathy is diabetic neuropathy, a condition that occurs in people with diabetes. It is the result of poorly controlled blood sugar levels. Though less common, diabetes can also cause mononeuropathy, often characterized by weakness of the eye or of the thigh muscles.
These are the most common symptoms of polyneuropathy:
- Loss of sensation in the arms and legs
Because people with chronic polyneuropathy often lose their ability to sense temperature and pain, they can burn themselves and develop open sores as the result of injury or prolonged pressure. If the nerves serving the organs are involved, diarrhea or constipation may result, as well as loss of bowel or bladder control. Sexual dysfunction and abnormally low blood pressure also can occur.
Joints are particularly vulnerable to stress in people with polyneuropathy because they are often insensitive to pain.
What Causes Peripheral Neuropathy
Peripheral neuropathy is the manifestation of many different conditions that can damage the peripheral nerves and is considered a neurological disorder rather than one distinct disease. Peripheral neuropathy may be either inherited or acquired.
Causes of acquired peripheral neuropathy include exposure to toxic chemicals, trauma, poor nutrition, alcoholism, protein abnormalities, autoimmune diseases, such as HIV/AIDS, Lyme Disease, Diphtheria and Leprosy, and systemic diseases such as Diabetes Mellitus, kidney disorders, cancers and benign tumors, and vitamin deficiencies.
Inherited forms of peripheral neuropathy are not common, and are caused by inborn mistakes in the genetic code or by new genetic mutations while in utero. The most common inherited neuropathies are a group of disorders referred to as Charcot-Marie-Tooth disease. This disease includes extreme weakening and wasting of muscles in the lower legs and feet, gait abnormalities, loss of tendon reflexes and numbness in lower limbs.
In some cases, however, even with extensive evaluation, the cause of a person’s peripheral neuropathy remains unknown—this is called idiopathic neuropathy, and accounts for almost a third of neuropathy cases today.
Peripheral Neuropathy Symptoms
Your symptoms will depend on the nerves that are affected. They can develop over days, weeks or years and can include:
- Pain: This can be mild or severe. It is described as burning, sharp, stabbing or like an electric shock. Some people lose the sensation of pain entirely.
- Numbness: This happens in your hands and feet first and then moves upwards. It is often described like wearing gloves or stockings when you are not. As a result, you may find it hard to do up buttons.
- Muscle weakness: This will depend on which muscle is affected. You may find it is difficult to walk, climb the stairs, hold a knife or fork, or that you are dropping things or stumbling.
- Sensation changes: You may feel heat or warmth when you touch something cold. You may also find that something that was not painful before now is. For example, bedclothes on your legs.
- Neurological: It may be difficult to keep your balance or you may get dizzy when you stand up. You may also feel very tired, have mood swings and have difficulty remembering things.
You most likely will not get all of these symptoms at the same time, and they will vary between different people.
There are no medical treatments known today that can cure peripheral neuropathy. If the specific cause of a patient’s neuropathy is known, further nerve damage can be prevented by eliminating the underlying cause, however, the focus of treatment is often on symptom control.
Mild pain may sometimes be alleviated by analgesics sold over the counter and more severe pain can sometimes be palliated with prescription drugs or by medical procedures. Other patients find that complementary and alternative therapies combined with other therapies help manage pain caused by peripheral neuropathy.
Mechanical aids and physical or occupational therapy can help reduce pain and lessen the impact of physical disability. Although some advances have been made in the diagnosis and treatment of peripheral neuropathies, it is not uncommon for the cause of a patient’s neuropathy to remain unidentified, and many patients continue to experience pain and disability despite available therapies.
In general, adopting healthy habits such as maintaining optimal weight by eating a well-balanced diet, avoiding exposure to toxins, following a physician-supervised exercise program, correcting vitamin deficiencies, and limiting or avoiding alcohol consumption can reduce the physical and emotional effects of peripheral neuropathy.
Active and passive forms of exercise can reduce cramps, improve muscle strength, and prevent muscle wasting in paralyzed limbs. Timely treatment of injury can help prevent permanent damage.
The best way to prevent peripheral neuropathy is to carefully manage any medical condition that puts you at risk. That means controlling your blood sugar level if you have diabetes or talking to your doctor about safe and effective treatments if you think you may have a problem with alcohol.
Whether or not you have a medical condition, eat a healthy diet that’s rich in fruits, vegetables, whole grains and lean protein. The best food sources of vitamin B-12 are meats, fish, eggs, low-fat dairy foods and fortified cereals. If you’re a strict vegetarian, fortified cereals are a good source of vitamin B-12 for you, but you may also want to talk to your doctor about B-12 supplements.
As much as possible, avoid repetitive motions, cramped positions and toxic chemicals, all of which may cause nerve damage.
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