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Periodic Paralysis Syndrome Symptoms & Diagnosis


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

Episodic bouts of severe weakness in the arms and legs are the most prominent symptom. Typically these bouts occur during sleep, especially 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 ( arrhythmias )
  • 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 (lasting 1-2 hours), 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, a condition 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.


Because this primarily is an inherited condition, the most important aspect of diagnosis is obtaining a family history. In addition to asking about symptoms and your medical history, your doctor will perform a physical exam.

Attacks don’t usually occur during an office visit, so your doctor may prescribe several blood tests to check potassium levels during an attack.

Your doctor may wish 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 to look for the gene mutation or to look for antibodies that may cause these types of symptoms.
  • Electrocardiogram (ECG, EKG)—a test that records the heart's activity by measuring electrical currents through the heart muscle
  • Electromyography (EMG)—to test the functioning of nerves and muscles

If the diagnosis is in question, your doctor may do a muscle biopsy .

Electromyography (EMG)

Electromyogram EMG
© 2009 Nucleus Medical Art, Inc.

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition. Copyright © 2020 EBSCO Publishing All rights reserved.

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