poly neuropathy

8/13/2019 Poly Neuropathy

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Polyneuropathy

Polyneuropathy is the simultaneous malfunction of many peripheral nerves throughout thebody. Infections, toxins, drugs, cancers, nutritional deficiencies, and disorders can cause many

peripheral nerves to malfunction.

Sensation, strength, or both may be impaired, often in the feet or hands before the arms,legs, or trunk.

Doctors base the diagnosis on results of electromyography, nerve conduction studies, andblood and urine tests.

If treating the underlying disorder does not relieve symptoms, physical therapy, drugs, andother

measures may help.Polyneuropathy may be acute (beginning suddenly) or chronic (developing gradually, often overmonths or years).Causes

Acute polyneuropathy has many causes: Infections involving a toxin produced by bacteria, as occurs in diphtheria

An autoimmune reaction (when the body attacks its own tissues), as occurs in Guillain-Barrsyndrome

Toxic substances, including heavy metals such as lead and mercury

Drugs, including the anticonvulsant phenytoin SOME TRADE NAMES

DILANTIN, some antibiotics (such as chloramphenicol SOME TRADE NAMES CHLORAMPHENICOL, nitrofurantoin SOME TRADE NAMES FURADANTINMACRODANTIN, and sulfonamides), some chemotherapy drugs (such as vinblastine and vincristine), andsome sedatives (such as barbital and hexobarbital)

Cancer, such as multiple myeloma, which damages nerves by directly invading or puttingpressure on them or by triggering an autoimmune reaction

The cause of chronic polyneuropathy is often unknown. Causes include the following: Diabetes

Excessive use of alcohol Nutritional deficiencies (such as thiamin deficiency), an uncommon cause in the United

States, except among alcoholics who are malnourished

Anemia due to vitamin B 12 deficiency (pernicious anemia)

An underactive thyroid gland (hypothyroidism)

Liver failure

Kidney failure


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Certain cancers, such as lung cancer

Vitamin B 6 (pyridoxine) taken in excessive amounts

The most common form of chronic polyneuropathy usually results from poor control of bloodsugar levels in people with diabetes (see Diabetes Mellitus (DM): Diabetes Mellitus ) but mayresult 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 toweakness, 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 musclemovement), sensory (which transmit sensory information), cranial nerves (which connect thehead, face, eyes, nose, muscles, and ears to the brain), or a combination.Symptoms

Acute polyneuropathy (for example, as occurs in Guillain-Barr syndrome) begins suddenly inboth 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, thefeet 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 legsare) are prominent symptoms. Because position sense is lost, walking and even standingbecome unsteady. Consequently, muscles may not be used. Eventually, they may weaken andwaste away.Diabetic neuropathy commonly causes painful tingling or burning sensations in the hands andfeet a condition called distal polyneuropathy. Pain is often worse at night and may beaggravated by touch or by a change in temperature. People may lose the senses of temperatureand pain, so they often burn themselves and develop open sores caused by prolonged pressureor 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.Polyneuropathy often affects the nerves of the autonomic nervous system, which controlsinvoluntary functions in the body (such as blood pressure, heart rate, digestion, salivation, andurination). Typical symptoms are constipation, loss of bowel or bladder control (leading to fecalor urinary incontinence), sexual dysfunction, and fluctuating blood pressure most notably asudden fall in blood pressure when a person stands up (orthostatic hypotension). The skin maybecome 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 maynot notice these symptoms or may consider them unimportant.How completely people recover depends on the cause of polyneuropathy.DiagnosisDoctors usually recognize polyneuropathy by the symptoms. A physical examination and testssuch as electromyography and nerve conduction studies (see Diagnosis of Brain, Spinal Cord,
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and Nerve Disorders: Electromyography and Nerve Conduction Studies ) can provide additionalinformation 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 isnecessary.Sometimes polyneuropathy affecting the hands and feet is the first indication that people havediabetes. Sometimes, when extensive testing detects no obvious cause, the cause is aninherited neuropathy that affects other family members so mildly that the disorder was neversuspected.TreatmentSpecific treatment depends on the cause, as for the following: Excessive amounts of vitamin B 6: If the vitamin is stopped, polyneuropathy may resolve. Diabetes: Careful control of blood sugar levels may slow progression of the disorder and

occasionally relieves symptoms. Transplantation of cells that produce insulin (islet cells seeTransplantation: Pancreas Transplantation ), located in the pancreas, sometimes results in acure.

Multiple myeloma or liver or kidney failure: Treatment of these disorders may result inslow recovery.

Cancer: Surgically removing the cancer may be necessary to relieve pressure on the nerve. An underactive thyroid gland: Thyroid hormone is given. Autoimmune disorders: Treatments include plasmapheresis (filtering of toxic substances,

including abnormal antibodies, from the blood), immune globulin given intravenously,corticosteroids, and drugs that suppress the immune system (immunosuppressants).

If the cause cannot be corrected, treatment focuses on relieving pain and problems related tomuscle weakness. Physical therapy sometimes reduces muscle stiffness and can preventshortening of muscles (contractures). Physical and occupational therapists can recommenduseful assistive devices. Some drugs that are usually not considered pain relievers can lessenpain due to nerve damage. They include the antidepressant amitriptyline, the anticonvulsantgabapentin SOME TRADE NAMES NEURONTIN, and mexiletine (used to treat abnormal heart rhythms). Lidocaine SOME TRADE NAMES XYLOCAINE, an anesthetic applied as a lotion, an ointment, or a skin patch, may also help.

GUILLAIN-BARR SYNDROMEGuillain-Barr syndrome (acute inflammatory demyelinating polyneuropathy) is a form ofpolyneuropathy that causes one episode of increasing muscle weakness. The episode lasts 8weeks or less. An autoimmune reaction may damage the myelin sheath around nerves.

Usually, weakness begins in both legs and moves up the body.

Electromyography and nerve conduction studies can help confirm the diagnosis.
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Plasmapheresis or immune globulin given intravenously may speed recovery.

The presumed cause is an autoimmune reaction: The body's immune system attacks the myelinsheath, 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 amild infection (such as a Campylobacter infection, mononucleosis, or another viral infection),surgery, or an immunization.SymptomsSymptoms 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 anda pins-and-needles sensation or loss of sensation. Weakness is more prominent than abnormalsensation. Reflexes are decreased or absent. In 90% of people who have Guillain-Barrsyndrome, weakness is most severe within 3 weeks. In 5 to 10%, the muscles that controlbreathing become so weak that a ventilator is needed. Because the facial and swallowingmuscles become weak, a few people need to be fed intravenously or through a tube placeddirectly through the abdominal wall into the stomach (gastrostomy tube).If the disorder is very severe, internal functions controlled by the autonomic nervous systemmay be impaired. For example, blood pressure may fluctuate widely, heart rhythm may becomeabnormal, and severe constipation may develop.In a variant called Miller-Fisher syndrome, only a few symptoms develop: Eye movementsbecome paralyzed, walking becomes difficult, and normal reflexes disappear.DiagnosisDoctors suspect the diagnosis based on the pattern of symptoms. Tests are done to confirm thediagnosis. People are usually admitted to the hospital to have the tests because the syndromecan worsen rapidly and impair the muscles involved in breathing.

Analysis of cerebrospinal fluid obtained by a spinal tap (lumbar puncture see Diagnosis ofBrain, Spinal Cord, and Nerve Disorders:Procedures ), electromyography, nerve conductionstudies, 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 noinflammatory cells in the cerebrospinal fluid and characteristic results from electromyographystrongly suggest Guillain-Barr syndrome.PrognosisDamage stops progressing within 8 weeks. Without treatment, most people improve slowly overseveral months. However, with early treatment, people can improve very quickly in days orweeks. About 30% of adults and even more children with the disorder have residual weakness 3years 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 inflammatorydemyelinating polyneuropathy (see Peripheral Nerve Disorders: Treatment ).TreatmentGuillain-Barr syndrome can worsen rapidly and is a medical emergency. People who developthis syndrome should be hospitalized immediately. Establishing the diagnosis is crucial becausethe sooner appropriate treatment is started, the better the chance of a good outcome.
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In the hospital, people are closely monitored so that breathing can be assisted with a ventilator ifnecessary. Nurses take precautions to prevent pressure sores and injuries by providing softmattresses and by turning the people with severe weakness every 2 hours. If weakness is lesssevere, physical therapy is started to help preserve joint and muscle function. Heat therapy maybe used first to relieve pain and thus make physical therapy more comfortable.Plasmapheresis (filtering of toxic substances, including antibodies to the myelin sheath) fromthe blood see Controlling Diseases by Purifying the Blood ) or immune globulin givenintravenously is the treatment of choice. These treatments are relatively safe, shorten thehospital stay, speed recover, and reduce the risk of death and permanent disability.Corticosteroids do not help and may worsen the syndrome.CHRONIC INFLAMMATORY DEMYELINATING POLYNEUROPATHYChronic inflammatory demyelinating polyneuropathy (chronic acquired demyelinatingpolyneuropathy, or chronic relapsing polyneuropathy) is a form of polyneuropathy that, likeGuillain-Barr syndrome, causes increasing muscle weakness, but the weakness lasts longerthan 8 weeks.

Chronic inflammatory demyelinating polyneuropathy develops in 3 to 10% of people withGuillain-Barr syndrome.Weakness and abnormal sensations (numbness and pins-and-needles) last longer than 8weeks. 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 occurless often, and other internal functions are less impaired than in people with Guillain-Barrsyndrome. Also, weakness may be more irregular, affecting the two sides of the body differently,and weakness may progress more slowly.Diagnosis and TreatmentDoctors 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 asazathioprine SOME TRADE NAMES IMURANmay also be used. However, if chronic inflammatory demyelinating polyneuropathy is severe orprogresses rapidly, plasmapheresis or immune globulin given intravenously may be preferred tocorticosteroids. People may need treatment for months or years.
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