Periodic Paralysis Syndrome

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.

  • 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.

    Genetic Material
    Chromosome DNA
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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

  • 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


    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:

    • Blood tests
    • Thyroid tests
    • Electrocardiogram
      (ECG, EKG)
    • Electromyography

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

    Electromyography (EMG)
    Electromyogram EMG
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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

  • 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

  • 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.

  • Treatment

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