What Is Asterixis?

Asterixis, also known as flapping tremor, is a movement disorder that makes it hard to hold the muscles of a limb in a fixed pose. It often affects the hands and arms, though it can also occur in other areas of the body.

Asterixis causes quick, uneven jerking movements after a brief muscle tone loss. When it appears in the hands and arms, the result compares to the flapping wings of a bird in flight.

This problem appears as a sign of some severe diseases. It is often linked with hepatic encephalopathy and other brain function issues. It is tied to certain drugs and brain lesions. Treatment involves finding the source and treating that problem.

This article describes asterixis symptoms, causes, diagnosis, and treatment.

Types of Asterixis

Asterixis is generally defined as being either bilateral or unilateral. Bilateral asterixis, which is the most common variety, affects both sides of the body. Unilateral asterixis involves one side.

Both types of asterixis occur as a sign of a more serious underlying condition. However, bilateral and unilateral asterixis vary in the types of diseases with which they are associated.

Bilateral asterixis is usually linked with one of several types of encephalopathies, which are diseases that affect brain function or structure. Unilateral asterixis is more likely to occur in patients with focal brain lesions.

Asterixis Symptoms

Asterixis symptoms are irregular, asynchronous (not happening at the same time), and variable in frequency and severity. In bilateral asterixis, one side may be affected more severely than the other. Asterixis symptoms may vary based on the disorder's underlying cause and the muscle group affected.

Symptoms of asterixis are not present when your muscles are at rest. Instead, the symptoms occur when you try to maintain a fixed position using the affected muscles. These muscles usually involve the hands and wrists, though the tongue, feet, and any skeletal muscles can be involved.

If you have asterixis and attempt to hold an affected body part steady, the following symptoms are likely to occur after a brief loss of muscle tone in the involved muscles:

• Negative myoclonus (sudden involuntary jerking of the muscle)
• Unsteady shaking
• Asynchronous tremors when both sides of the body are involved, except in facial muscles

Causes

Much remains unknown about the causes of asterixis. It is linked with a wide range of problems related to neurological (affecting the brain and nerves) and other types of disorders,

Research indicates that the condition occurs as a result of a malfunction in the primary motor cortex, an area of the brain that is key to initiating motor function. Another theory proposes that certain hyperactive brain cells cause fluid shifts in the brain that compromise the blood-brain barrier and impacts movement control.

The causes of bilateral asterixis mainly include metabolic encephalopathies, which affect brain function, and some types of drugs. Causes of bilateral asterixis include the following:

• Metabolic encephalopathies: Including liver failure, cardiac failure, respiratory failure, and azotemia (a buildup of blood urea nitrogen (BUN) in the body)
• Sedatives: Benzodiazepines and barbiturates
• Anticonvulsants:Dilanitin (phenytoin), Tegretol (carbamazepine), Depakote (valproic acid), and Neurontin (gabapentin)
• Antipsychotic: Lithium
• Antibiotic: Fortaz (ceftazidime)
• Antiemetic: Reglan (metoclopramide)
• Bilateral structural brain lesions
• Biochemical abnormalities: Hypomagnesemia (lower than normal magnesium levels) and hypokalemia (lower than normal postassium levels)

The cause of unilateral asterixis is linked to focal brain lesions in the following areas of the brain:

• Thalamus
• Corona radiata
• Anterior cerebral artery territory
• Primary motor cortex
• Parietal lobe
• Cerebellum
• Midbrain
• Pons

Diagnosis

The primary method of asterixis diagnosis is a physical examination and a test for asterixis in which you will be instructed to do the following:

1. Stand with your eyes closed.
2. Dorsiflex your wrists (bend them back toward your lower arm as though you were stopping traffic).
3. Spread your fingers, similar to pushing against a wall.

You will be asked to hold this position for up to 30 seconds. This allows your healthcare provider to test for the characteristic "flap" that occurs at the wrist in asterixis after a few seconds of holding out your wrist.

If your hip joint is involved, you will be asked to lie flat on your back with your knees bent up in an outward position while your feet are flat and then allow your knees to fall to the sides. A series of flapping movements will occur if asterixis is present.

Depending on your overall condition and symptoms, your healthcare provider may request one or more of the following tests to confirm the diagnosis:

• Blood tests to measure for chemical or mineral levels in your blood
• Computed tomography (CT) or magnetic resonance imaging (MRI) scans to examine brain function and identify damage or abnormalities that may be linked to your symptoms
• Electroencephalogram (EEG) to examine the brain's electrical activity and identify encephalopathy or stroke when present

Depending on the results of your tests, your healthcare provider may order additional tests or refer you to a specialist to identify the underlying condition causing your asterixis if it isn't already known. If you have a known preexisting condition, the diagnosis of asterixis may be used to determine your prognosis or state of disease.

Treatment

There is no specific treatment for asterixis. The recommended treatment is indirect because it is based on the underlying condition causing your symptoms. Treatment may also involve repair of the damage done to your liver, kidneys, brain, or nervous system before the treatment of asterixis.

For example, asterixis is the most widely recognized symptom of hepatic encephalopathy, a reversible syndrome that occurs in advanced liver disease. If your asterixis is linked to this condition, you may be advised of the following treatments:

• Take Xifaxan(rifaximin) to target bacteria.
• Discontinue and/or change certain medications that may be contributing to the problem.
• Take Generlac (lactulose) to prevent ammonia absorption and remove excess ammonia from the colon.
  
• Adhere to recommended lifestyle and dietary changes to reduce health risks.

Prognosis

The prognosis for patients with asterixis is relatively good. Treatment or improvement of the underlying condition causing asterixis can lead to reducing or eliminating the problem. For example, the symptoms of hepatic encephalopathy are usually reversible. The timing and degree of improvement vary depending on the severity of the underlying condition and the degree to which it can be treated and improved.

Coping

Living with asterixis can make it difficult to live normally, especially if your condition affects your hands and wrists. Your ability to perform daily tasks like writing, driving, and cooking may be affected.

The condition is generally temporary, so improvement depends on the progress you achieve in treating your underlying condition once the cause is found. Your healthcare provider will determine what treatment, if any is required to offset the effects of asterixis. If necessary, a combination of physical therapy, medication, and/or occupational therapy may help you cope with the disability that the tremors cause in your daily life.

Summary

Asterixis is a movement disorder that occurs as a sign of a more severe disease. It causes a loss of muscle tone followed by short tremors when you attempt to steady the muscles of an affected limb.

This problem often involves the hands and wrists. It can also impact your feet, hips, neck, lips, eyelids, or any other skeletal muscles.

When it affects the hands and arms, the result looks like the flapping wings of a bird in flight. The problem was first described as a liver flap since it was linked to hepatic encephalopathy, but it has been tied to many causes that affect brain function. Because of that, the name asterixis is preferred.

Treatment requires finding the source of the problem and treating that disease. When the cause is treated, control of the affected muscles improves and often returns to normal.

A Word From Verywell

Asterixis is not very common, but it can disrupt your ability to function normally when it occurs. In addition to causing an inconvenience, the condition is a symptom of a more serious problem. Contact your healthcare provider if you notice symptoms that align with this condition.

Getting a diagnosis as soon as problems begin can increase your chances of achieving the best results. The right treatment can improve your overall health and reduce or resolve asterixis symptoms.