What is periodic paralysis?

Periodic paralysis (PP) is a rare genetic disorder. It causes sudden attacks of short-term muscle weakness, stiffness, or paralysis. These attacks may affect the whole body or just one or two limbs. 

There are several different forms of PP. They all involve defects in ion channels. These are gateways that let charged minerals (ions) such as sodium and potassium flow into and out of your cells. This flow of ions is a central part of how your muscles work. In PP, the ion channels sometimes fail, and the muscle cells don’t work correctly. 

PP attacks can start in childhood or adulthood. They may happen after hard exercise or other triggers. Depending on the form of PP that you have, the symptoms may be mild or severe, and they may last for minutes or days. Sometimes, the disease may slowly get worse over time and cause permanent muscle damage. 

The main forms of PP are: 

• Hypokalemic PP (low potassium). Low blood levels of potassium may cause attacks. Other triggers may include heavy exercise, foods with a lot of sugars and starches (carbohydrates), licorice, stress, cold temperatures, and some medicines. This is the most common form of PP. 

• Hyperkalemic PP (high potassium). High blood levels of potassium may cause attacks. Other triggers may include heavy exercise, fasting, stress, cold, and some medicines. 

• Thyrotoxic PP. High levels of thyroid hormone may cause attacks. Thyroid-related problems are also usually present. Other triggers may include exercise, meals with a lot of carbohydrates, and stress. This form appears mostly in men, especially in those of Asian background.

• Andersen-Tawil syndrome. Swings in potassium blood levels may cause attacks. Triggers may also include exercise, stress, and certain medicines. Many people with this form of PP have a certain set of facial features. These include a broad forehead, widely spaced eyes, low-set ears, and a small chin. 

Most forms of PP affect the skeletal muscles. These are the muscles you control to move. Andersen-Tawil syndrome can affect the skeletal muscles and the heart muscle, making this form of PP more dangerous than the others.

What causes periodic paralysis?

The different forms of PP all result from genetic problems. These problems result in ion channel defects. The ion channels normally control the way that charged minerals (ions) such as potassium, sodium, and calcium enter and leave your muscle cells.

Each muscle cell has a covering, or membrane, which keeps the inside of the cell protected. When your nerve tells your muscle cell to contract, it sends a chemical signal that opens a gate to allow sodium ions to flow into the cell. The rush of charged ions changes the electrical charge inside the cell. This causes a wave of current through the muscle fiber. Calcium ions pour out of sacs in the cells and make the muscle fiber contract. Potassium channels open up, sending potassium ions out of the cell. This causes the muscle to contract. 

In PP, the ion channels have flaws that can disrupt the process. The muscle cells then fail to contract or relax in response to the nerve signals. 

There are many different defects that can cause PP. These affect sodium, calcium, or potassium ion channels. There are also many unidentified PP defects. In most cases, you can get PP if just one parent has the condition. 

What are the symptoms of periodic paralysis?

Your symptoms may depend somewhat on the form of PP you have. You may first notice symptoms in childhood or in adulthood. You may have attacks often or rarely. In some forms of PP, people tend to have less attacks as they get older. Generally, people with PP may have symptoms such as:  

• Attacks of muscle weakness that may last for minutes to days 

• Muscle pain in muscles after exercise 

• Muscle cramping 

• Feeling tingles 

• Permanent weakness (more likely later in life)

The different forms of PP may cause the following: 

• Hypokalemic PP often starts in the late childhood or teen years. The average is between 5 and 35 years of age. Attacks of skeletal muscle weakness may last from a couple of hours to a day. These tend to happen at night or in the morning. You may not be able to move at all during the most severe episodes. After about age 50, it may cause permanent weakness that slowly gets worse, especially in the hips and thighs. 

• Hyperkalemic PP often starts by age 10. Attacks of skeletal muscle weakness last an average of 30 minutes to 4 hours. The attacks tend to be frequent but less severe than in other PP forms. As you get older, you may have fewer attacks, but you also may have permanent muscle damage that slowly gets worse.

• Thyrotoxic PP tends to start between 20 and 40 years of age. Attacks happen anywhere from a few times per year to a few times per week. Attacks can last from hours to days. With this form of PP, you may also have thyroid-related symptoms such as anxiety, sweating, weight loss, and an abnormal feeling of the heartbeat (palpitations). Some people with thyrotoxic PP don't have symptoms of thyroid disease, especially early on.

• Andersen-Tawil syndrome usually starts before age 18. The attacks last from 1 to 36 hours. This form can cause irregular heartbeats because it affects heart muscle along with skeletal muscle. People with this disorder often have spine, dental, or jaw abnormalities.

In general, your symptoms may differ depending on the form of PP and the exact gene change that you may have. 

How is periodic paralysis diagnosed?

Your healthcare provider will take a health history. They will ask about your recent symptoms, past health problems, and family health history. Your provider will do a physical exam and assess your muscles. You may need tests such as: 

• Blood tests for potassium levels during an attack 

• Other blood tests to measure levels of other minerals and blood gases  

• Genetic blood tests for known PP defects 

• Nerve conduction studies and electromyography to measure the electrical activity of the muscles 

• An electrocardiogram (ECG) to check electrical activity of the heart  

• Blood tests to check levels of thyroid hormones 

You may first see your primary provider but then get referred to a neurologist who specializes in diseases such as PP.

How is periodic paralysis treated?

Treatment aims to reduce the number and severity of attacks. Ways to manage PP may include the following: 

• Closely control potassium intake through diet and supplements. 

• Use IV (intravenous) potassium treatments, if symptoms are severe from hypokalemic PP. 

• Control carbohydrates in the diet. 

• Control thyroid function. This is very important if you have thyrotoxic PP.

• Get help from a nutritionist. This expert can help you choose a diet that reduces attacks by decreasing changes in your carbohydrates or minerals.

• Take medicines such as acetazolamide. This medicine can make PP worse in some cases, though.

• Take other medicines such as carbonic anhydrase inhibitors or potassium-sparing diuretics. 

• Avoid certain types of anesthesia because of possible complications. 

• Use heart medicine or a pacemaker if you have Andersen-Tawil syndrome. 

• Limit exposure to triggers and keep exercise to a moderate level. 

• Take dichlorphenamide. This medicine can reduce the number of attacks if you have hypokalemic PP.

You may need frequent monitoring to measure your blood levels of potassium. A combination of controlled diet, medicines, and lifestyle changes may help you manage PP. 

Key points

• PP is a rare disorder that causes sudden, temporary attacks of muscle weakness, stiffness, or paralysis.

• PP is a genetic disorder passed down from a parent. The inheritance is dominant, meaning you have a chance of getting it if even one parent has the genetic defect for PP. 

• PP episodes can start in childhood or adulthood.

• The attacks may be mild or severe and may last for minutes or days. 

• Depending on the form of PP you have, attacks may result from low or high potassium levels in the blood, exercise, stress, cold, carbohydrate-rich meals, fasting, certain medicines, or high thyroid hormone levels. 

• Andersen-Tawil syndrome can affect the heart muscle, causing irregular heartbeats. 

• As people get older, they sometimes have permanent muscle damage. 

• You may use a combination of diet, medicines, and lifestyle changes to manage PP. 

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your provider if you have questions.