What tests are used to diagnose hypokalemic periodic paralysis?
If my blood potassium level is normal, does that prove I don't have hypokalemic periodic paralysis?
How widespread is the paralysis?
What is the inheritance pattern? What is the likelihood that people with a mutant gene will develop the condition?
What other diseases should be considered if one is considering a diagnosis of hypokalemic periodic paralysis?
- Normokalemic and hyperkalemic periodic paralysis (GeneReviews article here) and potassium-aggravated myotonia
- Paramyotonia congenita
- Andersen-Tawil syndrome (GeneReviews article here)
- Thyrotoxic periodic paralysis
- Autoimmune reactions to potassium channels
- Diseases of oxidative metabolism such as mitochondrial diseases
- Narcolepsy-cataplexy if there are hallucinations, sudden episodes of sleepiness, or trigger by laughing
- Low potassium caused by foods and drugs: licorice, barium exposure, diuretics, steroids and others
- Diseases in which potassium is chronically low because of kidney problems:
- Renal Tubular Acidosis
- Bartter syndromes and Gitelman hypomagnesemia-hypokalemia
- Sjögren syndrome
- Conn’s syndrome (hyperaldosteronism)
What other symptoms can co-occur with hypokalemic periodic paralysis?
- Pain (by some reports pain is more commonly associated with sodium-triggered episodes)
- Heart rhythm abnormalities
- Attention deficit disorder (ADD, ADHD)
- Relative insensitivity to the local anesthetic lidocaine and "dental anxiety"
- Severe premenstrual syndrome (PMS)
What other diagnoses are often given to people who have hypokalemic periodic paralysis?
- "Conversion disorder" is a label often applied to people with hypokalemic periodic paralysis, mistakenly attributing symptoms to "hysterical" or "functional" paralysis. Such mistaken diagnoses have occurred after episodes of whole body paralysis or after episodes of single limb paralysis.
Is it worth having a muscle biopsy?
Prevention and Effect of Food and Drugs
What exposures trigger paralysis?
- Carbohydrates: The best known trigger of hypokalemic periodic paralysis is eating a large amount of carbohydrates. The most common circumstance is a meal of pasta, which typically contains a large amount of simple carbohydrates that are broken down to sugars and released quickly into the blood. Other common triggers are sugar-containing drinks and large amounts of candy. Once in the blood, the sugars trigger release of insulin, which causes cells to take up the sugars and also take up potassium from the blood. The lowering of potassium triggers the paralysis in hypokalemic periodic paralysis. Consuming less carbohydrates is helpful, but often hard to achieve. Another approach is switching to slower-release forms of carbohydrates such as whole wheat pasta or shredded wheat cereal that spread out the absorption of sugar and reduce the drop in potassium. Of note, attacks from sugar loading can occur nearly instantaneously or occur hours later (for example, the morning following a pasta dinner).
- Salt: One of the most potent triggers of hypokalemic periodic paralysis is consumption of sodium chloride. The salt effect is far less known than the carbohydrate trigger, and many articles on hypokalemic periodic paralysis don't even mention this trigger. For many people it is easier to reduce salt than it is to reduce carbohydrates. Many foods contain huge amounts of salt, particularly snacks and tomato sauce. Restaurants and movie theatres will often add large amounts of salt to many foods, most notably pizza, nachos and snacks such as popcorn. Soda drinks that contain both sodium and sugar are a particular problem.
- Excitement / fear / epinephrine: Excitement or fear results in the body producing epinephrine, which makes episodes of paralysis more likely in some patients. Epinephrine injected to treat allergic reactions to foods, and epinephrine-like drugs such as albuterol used in asthma inhalers can trigger episodes of paralysis. This appears to be due to the effect of epinephrine in reducing blood potassium. The same pathway is often manipulated therapeutically: medications that block epinephrine effects such as beta-blockers are sometimes used to reduce the effect of epinephrine produced by the body. However, beta-blockers should be used only with caution, since they can produce severe problems in people with low blood pressure, slow heart rate (bradycardia) or asthma.
- Exercise: After strenuous exercise there is increased risk of symptoms of hypokalemic periodic paralysis.
- Cold environment: Muscles exposed to cold can become weak. Re-warming usually recovers muscle strength.
- Anesthesia: During anesthesia there are many changes that can contribute to paralysis, including cooling, glucose, sodium and certain anesthetics such as succinylcholine. It is not clear that people with hypokalemic periodic paralysis are at any increased risk for malignant hyperthermia.
- Alcohol: It is unclear why alcohol sometimes triggers periodic paralysis. It could be from electrolyte imbalance, dehydration, or increased exercise or dietary indiscretion that often accompanies the inebriated state.
- Electromagnetic fields: There are reports that electromagnetic fields can trigger episodes of paralysis in a subgroup of people with hypokalemic periodic paralysis, but this has not yet been studied in detail.
What exposures trigger problems other than paralysis?
- A subgroup of people with hypokalemic periodic paralysis appear to be particularly susceptible to heart rhythm abnormalities, especially when blood potassium is low but also at other times. Some people experience runs of slow heart rate (bradycardia) and fast heart rate (tachycardia), and many of these people are extremely sensitive to drugs that prolong the cardiac QT interval or drugs that increase heart rate.