Periodic Paralysis
Definition
Periodic
paralysis (PP) is the name for several rare, inherited muscle disorders marked by temporary weakness, especially following rest, sleep, or exercise.
Description
Periodic paralysis disorders are genetic disorders that affect muscle strength. There are two major forms, hypokalemic and hyperkalemic, each caused by defects in different genes.
In hypokalemic PP, the level of potassium in the blood falls in the early stages of a paralytic attack, while in hyperkalemic PP, it rises slightly or is normal. (The root of both words, "kali," refers to potassium.) Hyperkalemic PP is also called potassium-sensitive PP.
Causes and symptoms
Causes
Both forms of PP are caused by inheritance of defective genes. Both genes are dominant, meaning that only one copy of the defective gene is needed for a person to develop the disease. A parent with the gene has a 50% chance of passing it along to each offspring, and the likelihood of passing it on is unaffected by the results of previous pregnancies.
The gene for hypokalemic PP is present equally in both sexes, but leads to noticeable symptoms more often in men than in women. The normal gene is responsible for a muscle protein controlling the flow of calcium during muscle contraction.
The gene for hyperkalemic PP affects virtually all who inherit it, with no difference in male-vs.-female expression. The normal gene is responsible for a muscle protein controlling the flow of sodium during muscle contraction.
Symptoms
The attacks of weakness in hypokalemic PP usually begin in late childhood or early adolescence and often become less frequent during middle age. The majority of patients develop symptoms before age 16. Since they begin in the school years, the symptoms of hypokalemic PP are often first seen during physical education classes or after-school sports, and may be mistaken for laziness, or lack of interest on the part of the child.
Attacks are most commonly brought on by:
- strenuous exercise followed by a short period of rest
- large meals, especially ones rich in carbohydrates or salt
- emotional stress
- alcohol use
- infection
- pregnancy
The weakness from a particular attack may last from several hours to as long as several days, and may be localized to a particular limb, or might involve the entire body.
The attacks of weakness of hyperkalemic PP usually begin in infancy or early childhood, and may become less severe later in life. As in the hypokalemic form, attacks are brought on by stress, pregnancy, and exercise followed by rest. In contrast, though, hyperkalemic attacks are not associated with a heavy meal but rather with missing a meal, with high potassium intake, or use of glucocorticoid drugs such as prednisone. (Glucocorticoids are a group of steroids that regulate metabolism and affect muscle tone.)
Weakness usually lasts less than three hours, and often persists for only several minutes. The attacks are usually less severe, but more frequent, than those of the hypokalemic form. Weakness usually progresses from the lower limbs to the upper, and may involve the facial muscles as well.
Diagnosis
Diagnosis of either form of PP begins with a careful medical history and a complete physical and neurological exam. A family medical history may reveal other affected relatives. Blood and urine tests done at the onset of an attack show whether there are elevated or depressed levels of potassium. Electrical tests of muscle and a muscle biopsy show characteristic changes.
Challenge tests, to aid in diagnosis, differ for the two forms. In hypokalemic PP, an attack of weakness can be brought on by administration of glucose and insulin, with exercise if necessary. An attack of hyperkalemic PP can be induced with administration of potassium after exercise during
fasting. These tests are potentially hazardous and require careful monitoring.
Genetic tests are available at some research centers and are usually recommended for patients with a known family history. However, the number of different possible mutations leading to each form is too great to allow a single comprehensive test for either form, thus limiting the usefulness of
genetic testing.
Treatment
Severe respiratory weakness from hypokalemic PP may require intensive care to ensure adequate ventilation. Potassium chloride may be given by mouth or intravenously to normalize blood levels.
Attacks requiring treatment are much less common in hyperkalemic PP. Glucose and insulin may be prescribed. Eating carbohydrates may also relieve attacks.
Prognosis
Most patients learn to prevent their attacks well enough that no significant deterioration in the quality of life occurs. Strenuous exercise must be avoided, however. Attacks often lessen in severity and frequency during middle age. Frequent or severe attacks increase the likelihood of permanent residual weakness, a risk in both forms of periodic paralysis.
Prevention
There is no way to prevent the occurrence of either disease in a person with the gene for the disease. The likelihood of an attack of either form of PP may be lessened by avoiding the triggers (the events or combinations of circumstances which cause an attack) for each.
Hypokalemic PP attacks may be prevented with use of acetazolamide (or another carbonic anhydrase inhibitor drug) or a diuretic to help retain potassium in the bloodstream. These attacks may also be prevented by avoiding such triggers as salty food, large meals, a high-carbohydrate diet, and strenuous exercise.
Attacks of hyperkalemic PP may be prevented with frequent small meals high in carbohydrates, and the avoidance of foods high in potassium such as orange juice or bananas. Acetazolamide or thiazide (a diuretic) may be prescribed.
Resources
Organizations
Muscular Dystrophy Association. 3300 East Sunrise Drive, Tucson, AZ 85718. (800) 572-1717. http://www.mdausa.org.
Periodic Paralysis Association. 5225 Canyon Crest Drive #71-351, Riverside, CA 92507. (909) 781-4401. http://www.periodicparalysis.org.
Key terms
Gene — A biologic unit of heredity transmitted from parents to offspring.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
paralysis
[pah-ral´ĭ-sis] (pl. paral´yses.) Loss or impairment of motor function in a part due to a lesion of the neural or muscular mechanism; also, by analogy, impairment of sensory function (
sensory paralysis). Paralysis is a symptom of a wide variety of physical and emotional disorders rather than a disease in itself. Called also
palsy.
Types of Paralysis. Paralysis results from damage to parts of the nervous system. The kind of paralysis resulting, and the degree, depend on whether the damage is to the central nervous system or the peripheral nervous system.
If the central nervous system is damaged, paralysis frequently affects the movement of a limb as a whole, not the individual muscles. The more common forms of central paralysis are
hemiplegia (in which one entire side of the body is affected, including the face, arm, and leg) and
paraplegia (in which both legs and sometimes the trunk are affected). In
central paralysis the tone of the muscles is increased, causing
spasticity.
If the peripheral nervous system is damaged, individual muscles or groups of muscles in a particular part of the body, rather than a whole limb, are more likely to be affected. The muscles are flaccid, and there is often impairment of sensation.
Causes of Central Paralysis.
stroke syndrome is one of the most common causes of central paralysis. Although there is usually some permanent disability, much can be done to rehabilitate the patient. Paralysis produced by damage to the spinal cord can be the result of direct injuries, tumors, and infectious diseases. Paralysis in children may be a result of failure of the brain to develop properly in intrauterine life or of injuries to the brain, as in the case of
cerebral palsy. Congenital
syphilis may also leave a child partially paralyzed. Paralysis resulting from
hysteria has no organic basis and is a result of emotional disturbance or mental illness.
Causes of Peripheral Paralysis. Until the recent development of immunizing vaccines, the most frequent cause of peripheral paralysis in children was
poliomyelitis.
neuritis, inflammation of a nerve, can also produce paralysis. Causes can be physical, as with cold or injury; chemical, as in lead poisoning; or disease states, such as diabetes mellitus or infection. Paralysis caused by neuritis frequently disappears when the disorder causing it is corrected.
paralysis of accommodation paralysis of the ciliary muscles of the eye so as to prevent
accommodation.
ascending paralysis spinal paralysis that progresses upward.
birth paralysis that due to injury received at birth.
brachial paralysis paralysis of an upper limb from damage to the
brachial plexus.
bulbar paralysis that due to changes in motor centers of the medulla oblongata; the chronic form is marked by progressive paralysis and atrophy of the lips, tongue, pharynx, and larynx, and is due to degeneration of the nerve nuclei of the floor of the fourth ventricle.
central paralysis any paralysis due to a lesion of the brain or spinal cord.
cerebral paralysis paralysis caused by an intracranial lesion; see also
cerebral palsy.
compression paralysis that caused by pressure on a nerve.
conjugate paralysis loss of ability to perform some parallel ocular movements.
crossed paralysis paralysis affecting one side of the face and the other side of the body.
crutch paralysis brachial paralysis caused by pressure from a crutch.
decubitus paralysis paralysis due to pressure on a nerve from lying for a long time in one position.
Erb-Duchenne paralysis paralysis of the upper roots of the
brachial plexus due to destruction of the fifth and sixth cervical roots, without involvement of the small muscles of the hand. Called also
Erb's palsy.
facial paralysis weakening or paralysis of the facial nerve, as in
bell's palsy.
familial periodic paralysis a hereditary disease with recurring attacks of rapidly progressive flaccid paralysis, associated with a fall in (hypokalemic type), a rise in (hyperkalemic type), or normal (normokalemic type) serum potassium levels; all three types are inherited as autosomal dominant traits.
flaccid paralysis paralysis with loss of muscle tone of the paralyzed part and absence of
tendon reflexes.
infantile cerebral ataxic paralysis a congenital condition due to defective development of the frontal regions of the brain, affecting all extremities.
ischemic paralysis local paralysis due to stoppage of circulation.
Klumpke's paralysis (Klumpke-Dejerine paralysis) atrophic paralysis of the lower arm and hand, due to lesion of the eighth cervical and first dorsal thoracic nerves.
motor paralysis paralysis of the voluntary muscles.
periodic paralysis 1. any of various diseases characterized by episodic flaccid paralysis or muscular weakness.
Saturday night paralysis paralysis of the extensor muscles of the wrist and fingers, so called because of its frequent occurrence in alcoholics. It is most often due to prolonged compression of the radial (musculospiral) nerve, and, depending upon the site of nerve injury, is sometimes accompanied by weakness and extension of the elbow. Called also
musculospiral or
radial paralysis.
sensory paralysis loss of sensation resulting from a morbid process.
sleep paralysis paralysis occurring at awakening or sleep onset; it represents extension of the atonia of REM
sleep into the waking state and is often seen in those suffering from
narcolepsy or
sleep apnea. Called also
waking paralysis.
spastic paralysis paralysis with rigidity of the muscles and heightened deep muscle reflexes and
tendon reflexes.
tick paralysis progressive ascending flaccid motor paralysis following the bite of certain ticks, usually
Dermacentor andersoni; first seen in children and domestic animals in the northern Pacific region of North America, and now seen in other parts of the world.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.