Asterixis is a neurological disorder characterized by sudden, brief muscle twitching, due to an intermittent interruption in muscle tone. It is a specific sign of certain attacks of the central nervous system, found in encephalopathies and certain drug intoxications. People who have it cannot keep their hands in a stable position when reaching out. In this position, they present involuntary movements mainly of the hands and fingers, called wing beats, and limited and repeated movements. What are the causes ? Are there solutions to remedy this?

The term asterixis comes from the a-privative Greek and from the Greek word stêrizô which means “I remain stationary”. It is a neurological disorder corresponding to brief muscle relaxation followed by sudden muscle twitches. When the affected person has the arms outstretched forward, the hands extended and the fingers splayed, alternating movements of bringing the fingers together and apart, flexion and extension are observed at regular intervals. of the joints of the phalanges and the wrist. These movements are bilateral, asymmetric and asynchronous.

Asterixis is actually part of what is called negative myoclonus. Myoclonus corresponds to short involuntary abnormal movements characteristic of damage to the central nervous system. In the case of negative myoclonus, such as asterixis, it is caused by a sudden, brief and involuntary interruption in muscle postural tone.

Asterixis is characterized by particular movements, exhibiting the following characteristics:

• they evoke the beating of butterfly wings;
• they preferentially affect the limbs, especially the hands;
• they are slow, irregular and of great amplitude;
• they are successive of flexion-extension of the wrists and flexion-lateralization of the fingers;
• they are lateral at the level of the fingers.

Asterixis is sometimes referred to as flapping tremor. However, this term should be avoided since asterixis does not correspond to tremors of nervous origin.

The causes of myoclonus are very numerous. They all result from damage to the central nervous system and / or the spinal cord. Asterixis, in particular, is associated with:

• hepatic encephalopathy characteristic of hepatocellular insufficiency which usually occurs during cirrhosis of the liver or other acute or chronic liver damage, such as viral hepatitis or toxic hepatitis;
• respiratory encephalopathy related to excess carbon dioxide in the blood during acute respiratory failure;
• uremic encephalopathy associated with end-stage chronic renal disease;
• hypokalaemia, that is to say a too low level of potassium in the blood;
• toxic encephalopathies caused, for example, by lithium intoxication (treatment of bipolar disorders) linked to drug overdoses or by toxic comas linked to drug intoxication or exposure to toxic substances;
• lesions of different regions of the brain such as contralateral lesions of the thalamus, lesions of the parietal cortex or even lesions of the putamen.

The main function of the liver is to filter toxins from the body. But when the liver is weakened for some reason, it may not remove toxins effectively. As a result, they can accumulate in the blood and enter the brain, where they disrupt brain function. Likewise the kidneys, like the liver, also remove toxic substances from the blood. If too many toxins are allowed to build up, they can impair brain function and lead to asterixis. 

When asterixis is associated with cirrhosis, it can be spontaneous or caused by gastrointestinal bleeding, infection, or taking anxiolytics. It is undoubtedly due to the action on the brain of a certain quantity of ammonia poured into the general bloodstream, and following an insufficient functioning of the liver. This results in serious nervous disorders. 56% of people who developed asterixis related to alcohol-related liver disease died, compared to 26% of those who did not.

The risk factors for asterixis include all the factors that can affect brain function:

• stroke;
• diabetes ;
• high blood pressure ;
• lupus;
• certain genetic diseases
• Wilson’s disease, a genetic disease caused by the excessive accumulation of copper in the body, particularly in the liver and in the central nervous system;
• epilepsy;
• heart failure.

Asterixis is usually sought in a patient who is seated, upper limbs extended, hands dorsiflexed. If you have noticed any of the characteristic tremors of asterixis, or if you have any of the risk factors mentioned above, you should talk to your doctor. In many cases, when the condition that causes asterixis is successfully treated, the disorder improves or even goes away. 

Hepatic and uremic encephalopathies

• Lifestyle and diet changes, including reducing alcohol consumption;
• Laxatives: Lactulose, in particular, can speed up the elimination of toxins from the body.
• Antibiotics, such as rifaximin, reduce bacteria in the gut. Too much gut bacteria can lead to excessive ammonia build-up in the blood and impair brain function.
• Transplants: In severe cases of liver or kidney damage, the patient may need a healthy organ transplant.

Metabolic encephalopathy

• Diet modification;
• Taking medicines to fix the mineral which is in overabundance in the blood and eliminate it from the body.

Wilson’s disease

• Taking medicines such as zinc acetate, which prevents the body from absorbing copper from food ingested;
• Chelating agents, such as penicillamine, to help remove copper from tissue.