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Polyneuropathy is the simultaneous malfunction of many peripheral nerves throughout the body.
Polyneuropathy may be acute (beginning suddenly) or chronic (developing gradually, often over months or years).
Causes
Acute polyneuropathy has many causes:
The cause of chronic polyneuropathy is often unknown. Causes include the following:
The most common form of chronic polyneuropathy usually results from poor control of blood sugar levels in people with diabetes (see Diabetes Mellitus (DM): Diabetes Mellitus) but may result from excessive use of alcohol.
Diabetic neuropathy refers to the several forms of polyneuropathy that diabetes can cause. (Diabetes can also cause mononeuropathy or multiple mononeuropathy, which leads to weakness, typically of the eye or thigh muscles.)
In some people, the cause is hereditary.
Depending on the cause, polyneuropathies may affect motor nerves (which control muscle movement), sensory (which transmit sensory information), cranial nerves (which connect the head, face, eyes, nose, muscles, and ears to the brain), or a combination.
Symptoms
Acute polyneuropathy (for example, as occurs in Guillain-Barré syndrome) begins suddenly in both legs and progresses rapidly upward to the arms. Symptoms include weakness and a pins-and-needles sensation or loss of sensation. The muscles that control breathing may be affected, resulting in respiratory failure.
In the most common form of chronic polyneuropathy, only sensation is affected. Usually, the feet are affected first, but sometimes the hands are. A pins-and-needles sensation, numbness, burning pain, and loss of vibration sense and position sense (knowing where the arms and legs are) are prominent symptoms. Because position sense is lost, walking and even standing become unsteady. Consequently, muscles may not be used. Eventually, they may weaken and waste away.
Diabetic neuropathy commonly causes painful tingling or burning sensations in the hands and feet—a condition called distal polyneuropathy. Pain is often worse at night and may be aggravated by touch or by a change in temperature. People may lose the senses of temperature and pain, so they often burn themselves and develop open sores caused by prolonged pressure or other injuries. Without pain as a warning of too much stress, joints are susceptible to injuries. This type of injury is called Charcot's joints (see see Joint Disorders: Charcot's Joints).
Polyneuropathy often affects the nerves of the autonomic nervous system, which controls involuntary functions in the body (such as blood pressure, heart rate, digestion, salivation, and urination). Typical symptoms are constipation, loss of bowel or bladder control (leading to fecal or urinary incontinence), sexual dysfunction, and fluctuating blood pressure—most notably a sudden fall in blood pressure when a person stands up (orthostatic hypotension). The skin may become pale and dry, and sweating may be reduced.
People who have a hereditary form may have hammer toes, high arches, and a curved spine (scoliosis). Abnormalities in sensation and muscle weakness may be mild. Affected people may not notice these symptoms or may consider them unimportant.
How completely people recover depends on the cause of polyneuropathy.
Diagnosis
Doctors usually recognize polyneuropathy by the symptoms. A physical examination and tests such as electromyography and nerve conduction studies (see Diagnosis of Brain, Spinal Cord, and Nerve Disorders: Electromyography and Nerve Conduction Studies) can provide additional information about absent or reduced sensation in the feet.
After polyneuropathy is diagnosed, its cause, which may be treatable, must be identified. Doctors ask whether other symptoms are present and how quickly the symptoms developed. Blood and urine tests may detect a disorder that is causing polyneuropathy—for example, diabetes, kidney failure, or an underactive thyroid gland. Infrequently, a nerve biopsy is necessary.
Sometimes polyneuropathy affecting the hands and feet is the first indication that people have diabetes. Sometimes, when extensive testing detects no obvious cause, the cause is an inherited neuropathy that affects other family members so mildly that the disorder was never suspected.
Treatment
Specific treatment depends on the cause, as for the following:
If the cause cannot be corrected, treatment focuses on relieving pain and problems related to muscle weakness. Physical therapy sometimes reduces muscle stiffness and can prevent shortening of muscles (contractures). Physical and occupational therapists can recommend useful assistive devices. Some drugs that are usually not considered pain relievers can lessen pain due to nerve damage. They include the antidepressant amitriptyline, the anticonvulsant gabapentin, and mexiletine (used to treat abnormal heart rhythms). Lidocaine, an anesthetic applied as a lotion, an ointment, or a skin patch, may also help.
Guillain-Barré Syndrome
Guillain-Barré syndrome (acute inflammatory demyelinating polyneuropathy) is a form of polyneuropathy that causes one episode of increasing muscle weakness. The episode lasts 8 weeks or less.
The presumed cause is an autoimmune reaction: The body's immune system attacks the myelin sheath, which surrounds the axon of many nerves and enables nerve impulses to travel quickly. In about 80% of people with this syndrome, symptoms begin about 5 days to 3 weeks after a mild infection (such as a Campylobacter infection, mononucleosis, or another viral infection), surgery, or an immunization.
Symptoms
Symptoms usually begin in both legs, then progress upward to the arms. Occasionally, symptoms begin in the arms or head and progress downward. Symptoms include weakness and a pins-and-needles sensation or loss of sensation. Weakness is more prominent than abnormal sensation. Reflexes are decreased or absent. In 90% of people who have Guillain-Barré syndrome, weakness is most severe within 3 weeks. In 5 to 10%, the muscles that control breathing become so weak that a ventilator is needed. Because the facial and swallowing muscles become weak, a few people need to be fed intravenously or through a tube placed directly through the abdominal wall into the stomach (gastrostomy tube).
If the disorder is very severe, internal functions controlled by the autonomic nervous system may be impaired. For example, blood pressure may fluctuate widely, heart rhythm may become abnormal, and severe constipation may develop.
In a variant called Miller-Fisher syndrome, only a few symptoms develop: Eye movements become paralyzed, walking becomes difficult, and normal reflexes disappear.
Diagnosis
Doctors suspect the diagnosis based on the pattern of symptoms. Tests are done to confirm the diagnosis. People are usually admitted to the hospital to have the tests because the syndrome can worsen rapidly and impair the muscles involved in breathing.
Analysis of cerebrospinal fluid obtained by a spinal tap (lumbar puncture—see Diagnosis of Brain, Spinal Cord, and Nerve Disorders: Tests for Brain, Spinal Cord, and Nerve Disorders ), electromyography, nerve conduction studies, and blood tests can help doctors exclude other possible causes of severe weakness, such as transverse myelitis and spinal cord injuries. A combination of high protein levels and no inflammatory cells in the cerebrospinal fluid and characteristic results from electromyography strongly suggest Guillain-Barré syndrome.
Prognosis
Damage stops progressing within 8 weeks. Without treatment, most people improve slowly over several months. However, with early treatment, people can improve very quickly—in days or weeks. About 30% of adults and even more children with the disorder have residual weakness 3 years after the syndrome began. On average, less than 2% of people die.
After improving initially, 3 to 10% of people develop a disorder called chronic inflammatory demyelinating polyneuropathy (see Peripheral Nerve Disorders: Treatment).
Treatment
Guillain-Barré syndrome can worsen rapidly and is a medical emergency. People who develop this syndrome should be hospitalized immediately. Establishing the diagnosis is crucial because the sooner appropriate treatment is started, the better the chance of a good outcome.
In the hospital, people are closely monitored so that breathing can be assisted with a ventilator if necessary. Nurses take precautions to prevent pressure sores and injuries by providing soft mattresses and by turning the people with severe weakness every 2 hours. If weakness is less severe, physical therapy is started to help preserve joint and muscle function. Heat therapy may be used first to relieve pain and thus make physical therapy more comfortable.
Plasmapheresis (filtering of toxic substances, including antibodies to the myelin sheath) from the blood—see Controlling Diseases by Purifying the Blood ) or immune globulin given intravenously is the treatment of choice. These treatments are relatively safe, shorten the hospital stay, speed recover, and reduce the risk of death and permanent disability.
Corticosteroids do not help and may worsen the syndrome.
Chronic Inflammatory Demyelinating Polyneuropathy
Chronic inflammatory demyelinating polyneuropathy (chronic acquired demyelinating polyneuropathy, or chronic relapsing polyneuropathy) is a form of polyneuropathy that, like Guillain-Barré syndrome, causes increasing muscle weakness, but the weakness lasts longer than 8 weeks.
Chronic inflammatory demyelinating polyneuropathy develops in 3 to 10% of people with Guillain-Barré syndrome.
Weakness and abnormal sensations (numbness and pins-and-needles) last longer than 8 weeks. Weakness can worsen continually or come and go. Reflexes are decreased or absent. In most people with this disorder, blood pressure fluctuates less, abnormal heart rhythms occur less often, and other internal functions are less impaired than in people with Guillain-Barré syndrome. Also, weakness may be more irregular, affecting the two sides of the body differently, and weakness may progress more slowly.
Diagnosis and Treatment
Doctors suspect the diagnosis based on symptoms. Electromyography, nerve conduction studies, and a spinal tap to obtain cerebrospinal fluid are done to confirm the diagnosis. Rarely, a biopsy of the nerve is needed.
Corticosteroids such as prednisone can relieve symptoms. Immunosuppressants such as azathioprine may also be used. However, if chronic inflammatory demyelinating polyneuropathy is severe or progresses rapidly, plasmapheresis or immune globulin given intravenously may be preferred to corticosteroids. People may need treatment for months or years.
Last full review/revision February 2008 by Michael Rubin, MD
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