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Definition  

Periodic paralysis is a rare condition that is usually inherited. It causes occasional episodes of severe muscle weakness. The two most common types of periodic paralysis are hypokalemic and hyperkalemic.

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Genetic Material  
Chromosome_DNA

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Causes  

Periodic paralysis is a condition that is present from birth. Familial periodic paralysis is inherited, but may occur without a known family history. Periodic paralysis is caused by abnormalities of the electrolyte channels on muscles.

With the inherited form of the disorder, only one affected parent is needed to transmit the gene to the baby. Rarely, the condition occurs as a result of a noninherited genetic defect.

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Risk Factors  

Factors that increase your chance of developing periodic paralysis include:

  • Family history of periodic paralysis
  • Thyroid disorder—high thyroid hormone levels, particularly in Asian males
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Symptoms  

Although muscle strength returns to normal between attacks, repeated episodes of weakness may lead to chronic muscle weakness later in life. The person remains alert and aware during attacks. There is no loss of sensation.

Episodes of severe weakness in the arms and legs are the major symptom. Typically, these episodes occur during sleep, early morning, or after strenuous activity. Cold, stress, and alcohol may also produce attacks. Other, less common, symptoms may include:

  • Weakness in the eyelids and face muscles
  • Muscle pain
  • Irregular heartbeats
  • Difficulty breathing or swallowing—This requires emergency care.

Some features are specific to the type of periodic paralysis.

  • Hypokalemic:
    • Potassium levels are low during attacks
    • Frequency of attacks varies from daily to yearly
    • Attacks usually last between 4-24 hours, but can last for several days
    • Attacks usually begin in adolescence, but they can occur before age 10
  • Hyperkalemic:
    • Potassium levels are high or normal during attacks
    • Attacks are usually shorter, more frequent , and less severe than the hypokalemic form; breathing and swallowing difficulties are extremely rare
    • Between attacks, patients often experience muscle spasms or difficulty relaxing their muscles. This condition is known as myotonia
    • Attacks usually begin in early childhood

Persons with some types of periodic paralysis are at risk for a condition known as malignant hyperthermia. This can occur during the use of general anesthesia . Anyone with a family history of periodic paralysis needs to notify the anesthesiologist of this history prior to any surgery.

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Electromyography (EMG)  
Electromyogram EMG

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Diagnosis  

Because this primarily is an inherited condition, the most important part of diagnosis is obtaining a family history. Your doctor will ask about symptoms and your medical history. A physical exam will be done.

Attacks do not usually occur during an office visit. Your doctor may order several blood tests and thyroid tests to check potassium levels during an attack.

Your doctor may want to bring on an attack during an office visit. This should only be done under careful monitoring by an experienced neurologist. If an attack is triggered, several tests may be done, including:

Your muscle tissue may need to be tested. This can be done with a biopsy .

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Treatment  

Since there is no cure for periodic paralysis, lifelong treatment is usually required. Treatment focuses on preventing attacks and relieving symptoms.

Lifestyle Changes  

There are a few behaviors you can adopt to reduce the frequency and severity of attacks:

  • Hypokalemic:
  • Hyperkalemic:

Medications  

The type of medications prescribed depend on the type of periodic paralysis.

  • Medications for both hypokalemic and hyperkalemic include:
    • Acetazolamide may prevent an attack by reducing the flow of potassium from the bloodstream into the cells of the body.
  • Hypokalemic:
    • Potassium may stop an attack; intravenous potassium may be prescribed for severe weakness.
    • Avoiding certain commonly prescribed medications may help reduce the onset of attacks.
    • If you have a thyroid condition, be sure to get treatment for it.
  • Hyperkalemic:
    • Thiazide diuretics, or water pills, may be prescribed to prevent an attack.
    • Glucose and insulin, or calcium carbonate may be prescribed to slow or stop an attack.
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Prevention  

Familial periodic paralysis cannot be prevented. Because it can be inherited, genetic counseling may be advised for couples at risk of passing on the disorder.

For the hypokalemic type, attacks may be reduced by:

  • Avoiding corticosteroids and glucose infusions
  • Following a diet low in carbohydrates and sodium and rich in potassium

For the hyperkalemic type, attacks may be reduced by:

  • Avoiding high potassium foods, fasting, and drugs known to increase potassium levels
  • Engaging in regular, mild exercise