periodic paralysis

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Periodic Paralysis



Periodic paralysis (PP) is the name for several rare, inherited muscle disorders marked by temporary weakness, especially following rest, sleep, or exercise.


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


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.


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 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.


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.


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.


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.



Muscular Dystrophy Association. 3300 East Sunrise Drive, Tucson, AZ 85718. (800) 572-1717.
Periodic Paralysis Association. 5225 Canyon Crest Drive #71-351, Riverside, CA 92507. (909) 781-4401.

Key terms

Gene — A biologic unit of heredity transmitted from parents to offspring.


 [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.
paralysis a´gitans Parkinson's disease.
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.
divers' paralysis decompression sickness.
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.
immunologic paralysis former name for immunologic tolerance.
infantile paralysis the major form of poliomyelitis.
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.
Landry's paralysis Guillain-Barré syndrome.
lead paralysis severe peripheral neuritis with wristdrop, due to lead poisoning.
mixed paralysis combined motor and sensory paralysis.
motor paralysis paralysis of the voluntary muscles.
musculospiral paralysis Saturday night paralysis.
obstetric paralysis birth paralysis.
periodic paralysis
1. any of various diseases characterized by episodic flaccid paralysis or muscular weakness.
progressive bulbar paralysis the chronic form of bulbar paralysis; called also Duchenne's disease or paralysis.
pseudobulbar muscular paralysis pseudohypertrophic muscular dystrophy.
pseudohypertrophic muscular paralysis pseudohypertrophic muscular dystrophy.
radial paralysis Saturday night paralysis.
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.
spastic spinal paralysis lateral sclerosis.
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.
Volkmann's paralysis ischemic paralysis.
waking paralysis sleep paralysis.

per·i·od·ic pa·ral·y·sis

Inclusive term for three familial muscle disorders characterized by recurring episodes of weakness or flaccid paralysis without loss of consciousness or alterations in speech or sensation; the attacks typically begin when the patient is at rest and may last for an hour or so to a few days; between attacks, the patient typically enjoys good health; due to mutation of either the gene encoding the alpha subunit of the sodium channel of skeletal muscle on chromosome 17q23 (hyperkalemic period paralysis, normokalemic periodic paralysis) or to the gene that encodes the alpha subunit of the calcium channel on chromosome 1q31-q32 (hypokalemic periodic paralysis). The periodic paralyses are now grouped with the myotonic disorders, because all are ion channel diseases, or "channelopathies." See: hyperkalemic periodic paralysis, hypokalemic periodic paralysis, normokalemic periodic paralysis.

periodic paralysis

Neurology Any of a group of conditions characterized by centrifugal 'attacks' of paralyzing, focal or systemic weakness of hrs to days in duration, accompanied by a loss of deep tendon reflexes, refractoriness of muscle fibers to electrical stimulation, profound changes in potassium levels, variable cardiac arrhythmias and complete recuperation between attacks; rest following vigorous exercise may evoke an attack in a group of muscle fibers without changing the serum K+ levels
Periodic paralysis
Hypokalemic periodic paralysis Periodic paralysis I An AD condition of late onset that is more intense in ♂ and occurs following strenuous exercise or carbohydrate meals, affecting the extremities, respiratory and cardiac muscle, potentially causing ventricular tachycardia and premature ventricular contractions Treatment KCl, acetazolamide; the severely afflicted may develop persistent weakness and dystrophic changes in muscle DiffDx Carnitine palmityl transferase deficiency, glycogen storage disease, type V, all other forms of periodic paralysis
Hyperkalemic periodic paralysis Periodic paralysis II An AD variant of muscular dystrophy caused by a defective gene on chromosome 17, which encodes the α subunit of a sodium channel in muscle cell membranes, closely linked to the growth hormone gene GH1 Clinical Early onset, most intense in males in whom paralytic attacks follow strenuous exercise, affecting the legs and eyelids; hyperkalemia may be prevented by acetazolamide; with time, severely afflicted subjects develop persistent weakness and dystrophic changes in muscle
Normokalemic periodic paralysis Periodic paralysis III
1. Primary or hereditary A condition with attacks of childhood onset that may disappear by middle age; exposure to cold may provoke attacks and over time, result in vacuolar myopathy; the attacks may be provoked by high-carbohydrate, high-sodium diets during periods of excitement and may respond to oral potassium.
2. Secondary or acquired A condition associated with thyrotoxicosis, hypokalemia or K+ wasting by the kidneys or GI tract or due to accidental ingestion of absorbable barium salts that block K+ channels, reducing the egress of K+ from the muscles, evoking systemic hypokalemia or hyperkalemia, which may be associated with renal or adrenal insufficiency  

per·i·od·ic pa·ral·y·sis

(pēr'ē-od'ik păr-al'i-sis)
Term for a group of diseases characterized by recurring episodes of muscular weakness or flaccid paralysis without loss of consciousness, speech, or sensation; attacks begin when the patient is at rest, and there is apparent good health between attacks.
See: hyperkalemic periodic paralysis, hypokalemic periodic paralysis, normokalemic periodic paralysis