Asterixis

What is asterixis?

Asterixis is a symptom that causes your muscles to relax briefly while using them. Depending on which muscles you’re using, it can look like flapping or tremor-like movements.

Asterixis is a form of negative myoclonus (pronounced “my-OCK-lon-us”). The term “negative” here doesn’t mean “bad.” Positive myoclonus is a sudden, brief muscle twitch or spasm, so positive here means “more activity.” Negative myoclonus is when a flexed muscle suddenly relaxes, so negative means "less activity.”

This symptom can happen because of issues that are directly affecting your brain. It can also be a secondary condition, meaning something else is affecting your brain and causing asterixis.

What does asterixis look like?

Asterixis affects muscle movements. Most of the time, it affects both sides of your body. But it may not affect both sides of your body as strongly. One side may be affected more strongly or the muscle movements may not be synchronized. It’s common for asterixis to be associated with sleepiness, mental confusion or disorientation.

The most common way healthcare providers will look for this is by having you hold your wrists and hands in certain ways. There are other methods to see asterixis that involve your legs and feet. But hand-related methods are the most commonly used.

The hand-related methods that providers can look for asterixis include:

• Palms-out method. A healthcare provider will have you extend your arms forward. You’ll spread your fingers and hold your hands like you’re pushing against an invisible wall with the flat surfaces of your palms. That flexes muscles in your wrist. Asterixis will cause your hands to “flap” when those muscles briefly stop flexing.
• Grip method. A healthcare provider using this method will have you grip their hands with yours. They’ll ask you to squeeze tightly and hold your grip. Asterixis will cause split-second losses of grip strength that the provider can feel.

Asterixis commonly doesn’t show right away during either of these methods. Your provider may have you hold the position for 30 seconds or more to be sure they don’t miss it.

What are the most common causes of asterixis?

Asterixis can happen for several reasons, but the most common ones involve certain types of organ failure. Medications and other conditions may also cause it.

Organ-related conditions

Your liver and kidneys filter toxic substances out of your blood. When your liver and kidneys aren’t working properly, toxic substances can build up in your blood. Your brain is sensitive to many of those substances, so that buildup can disrupt brain function and damage brain cells.

Organ-related conditions that can interfere with liver and kidney function and lead to asterixis include:

• Cirrhosis.
• Liver cancer.
• Liver disease.
• Liver failure.
• Kidney disease.
• Kidney failure.

Brain injuries

Injuries to your brain can cause brain lesions. These lesions are areas that don’t work properly because of damage or other kinds of disruptions that affect their cells. When these lesions affect certain areas responsible for muscle control, it can cause asterixis. When this happens, asterixis is usually one-sided.

Other conditions

Many other conditions can also cause or contribute to asterixis. Almost all of them have to do with changes in your blood chemistry. Examples include:

• Electrolyte imbalances, especially low blood sugar (hypoglycemia), low potassium (hypokalemia) and low magnesium (hypomagnesemia).
• Heart failure.
• Respiratory failure (especially when it causes carbon dioxide buildup in your blood).
• Wilson disease (a genetic condition that causes copper to build up, affecting your brain.

Medications-related asterixis

Certain medications that affect your nervous system can also cause asterixis as a temporary side effect. People with reduced kidney or liver function may also be more prone to asterixis from medications.

These medications include:

• Antiseizure medications, especially phenytoin (asterixis is often called “phenytoin flap” when that drug is the cause). Other antiseizure medications like gabapentin, valproate and carbamazepine can also cause it.
• Barbiturates.
• Benzodiazepines.
• Certain antibiotics (especially cephalosporins such as cefepime and ceftazidime).
• Lithium (mood stabilizer).
• Metoclopramide (antinausea).

How is asterixis treated?

Asterixis isn’t treatable directly. Instead, healthcare providers will try to find the cause and treat it. Treating the cause generally improves this symptom. Because there are many different causes, the treatment options vary widely. Your healthcare provider (or a provider caring for a loved one with this symptom) can tell you more about possible treatments and which they recommend.

What can I do at home to treat asterixis?

Asterixis isn’t a symptom that you can self-diagnose or self-treat. Because it happens with conditions that are very serious (or even deadly), you should talk to a healthcare provider if you think you have this symptom.

What are the possible complications or risks of not treating asterixis?

The biggest risk from not diagnosing and treating asterixis is from unmanaged or severe medical conditions that might be causing it. In addition to being life-threatening, some untreated medical conditions causing asterixis can also cause brain damage, resulting in permanent difficulties with thinking, mobility, and arm and leg use.

When asterixis affects your legs or muscles of your trunk (chest, abdomen and back), it can create serious issues. Asterixis can result in falls, which can result in injuries.

Is asterixis preventable?

Asterixis generally isn’t preventable because it happens unpredictably. It also isn’t usually one of the first symptoms of a condition that can cause it.

The only form of asterixis that’s preventable is medication-related asterixis. To prevent it, take medications exactly as prescribed by your healthcare provider. If you notice any side effects, like asterixis, from a prescribed medication, call your healthcare provider right away. You should also avoid nonmedical drug use of any kind.

When should asterixis be treated by a doctor or healthcare provider?

You should always see a healthcare provider if you think you have asterixis. Some symptoms mean asterixis is more serious.

If you have (or a loved one has) asterixis and feel confused, disoriented or show other mental changes, these symptoms need immediate medical attention. Those are signs that brain activity disruptions are more severe and could become dangerous.

A note from Cleveland Clinic

Asterixis is a symptom that might mean there’s an issue affecting your brain. While most healthcare providers associate it with liver or kidney problems, there are other possible causes, too. Treating whatever’s causing asterixis is the main approach to resolving this issue. If you have questions about asterixis, what’s causing it and how to treat it in you or a loved one, a healthcare provider can offer guidance and information.