Asterixis: what is it, types, associated symptoms and treatment

Asterixis is a motor disorder present in various liver, kidney, respiratory, heart and brain disorders.

It manifests itself in the form of tremors, similar to those that a bird makes when flapping, and can be caused by many different causes. Let us delve further into what are the characteristics of this clinical sign.

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What is asterixis?

The asterixis (from the Greek "a" and "sterig", "not to hold") is a clinical sign used to describe a neuromuscular disorder consisting of the involuntary appearance of rhythmic interruptions of a muscle contraction, and is usually manifested generally by tremors in the wrist, metacarpophalangeal and hip joints. This problem usually affects both hands, although it can also affect only one in particular.

This problem is also called liver tremors or flaps (liver flaps) and was first described in 1949 in patients with severe liver failure and encephalopathy. These muscle movements are totally involuntary and generally appear when the arms are extended and the wrists flexed.

It is difficult for patients with this medical condition to keep the affected body part stable..

Despite having the appearance of a tremor and are often called that, actually asterixis It is not considered a tremor in the strict sense of the word, but rather repetitive contractions produced by repeated relaxations of the muscles engaged in spontaneous movements. However, when a patient is seen suffering from this motor disorder, his physical behavior resembles that of a bird that is moving its wings, which is why in the most everyday language they are called tremors

In most cases this condition develops in the hands, but it is not exclusive to that area. Involuntary flapping can also be observed in other parts of the human body, such as the eyelids, in the form of trembling of the lips and the tongue or involuntary movement of the ankles and feet would also be signs of asterixis.

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Associated symptoms

Asterixis is a motor disorder whose main symptom is the most visible: involuntary shaking or flapping of parts of the body, especially in the hands and wrists. This tremor usually consists of a sudden and irregular movement, with a frequency of 3 to 5 Hz that occurs when the person stretches the arms and flexes the wrists. It is difficult for the person to maintain a completely fixed position.

This phenomenon can involve pain in the joints and muscles, as well as weakness and discomfort. As we have commented, other parts of the body can also present a motor alteration that would be considered as asterixis per se, such as the jaw, tongue, neck and eyelids.

A patient with asterixis may show other symptoms depending on the cause of his motor disorder.. An example of this is bilateral asterixis caused by a metabolic encephalopathy that usually presents highly developed symptoms. In this case, this condition can also be accompanied by a mental state due to the irregular levels of neurotransmitters circulating in the blood and causing behavior gallant.

Although asterixis is a motor condition, it can be accompanied by symptoms such as jaundice (yellowing of the skin) due to accumulation of bilirubin, swelling or edema in the feet, cramps caused by an imbalance of electrolytes and diarrhea which can be accompanied by bleeding. There may also be bleeding gums, blood in the urine, and vomiting of blood (hematemesis).

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Types of asterixis

There can be several causes behind a case of asterixis, ranging from diseased organs to brain injuries. Based on this, asterixis is classified mainly into two types.

1. Bilateral

Among the most common causes of bilateral asterixis we have metabolic encephalopathies, especially liver and kidney.

Alterations in kidneys and in the liver they are especially harmful for the body in general and for the brain in particular, because Failure to work properly produces imbalances in the levels of electrolytes and other chemicals in blood. When organic homeostasis is lost, both the brain and other organs stop working properly and this can be evidenced in the form of asterixis.

It is important to highlight the specific link between this type of asterixis and the liver and kidneys. These three organs play a very important role in the body's metabolism, since they are responsible for eliminating toxic waste from the body, either by metabolizing and inactivating them or, directly, by eliminating them from the body through the excretion.

One of the main wastes produced by the body's metabolism is nitrogen. This substance, when it is not eliminated properly, ends up incorporating other proteins in the blood and the converted into aberrant neurotransmitters, which cause the peripheral tremors so characteristic of the asterixis.

It must be said that changes in the liver and kidneys are not the only potential causes behind a case of asterixis. Also heart and respiratory diseases, in addition to substance intoxication can be behind a case of this type of asterixis.

2. Unilateral

Unilateral asterixis it is mainly caused by focal brain lesions in the genu (knee) area of ​​the internal capsule and the ventrolateral thalamus.

This is because it is in this region where direct nerve fibers exit from the cerebral cortex with motor action. Lesions in the midbrain, parietal cortex and the medial frontal cortex can also be causes of unilateral asterixis.

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Related pathologies

There are several medical conditions in which we can find asterixis as a symptom, both directly and indirectly related.

Hepatic encephalopathy is a condition of its own in patients with cirrhosis. This problem causes brain deterioration that is accompanied by various alterations at a psychological level, such as changes in personality and confusion. Added to this, and as we have discussed in the section on bilateral asterixis, hepatic encephalopathy can cause the characteristic tremors of asterixis.

Another condition in which this motor disorder can occur is severe respiratory failure. This breathing problem is caused when the lungs find it difficult to absorb oxygen. and release carbon dioxide, which causes headaches and significant loss of reflexes. When the critical point is reached, asterixis can manifest, almost immediately before the patient falls into a coma.

We can also talk about uremic syndrome, a kidney disorder that occurs when the kidneys are malfunctioning. As this medical condition worsens, it can result in asterixis as the person progressively loses control of their voluntary motor movement.

Finally we have the fact that substance intoxication can result in this motor disorder. Among the substances that can cause asterixis we mainly have alcohol and medications, including barbiturates, carbamazepine, gabapentin, valproate, lithium, ceftazidime and metoclopramide, drugs that all have this motor disorder as a potential side effect.

Other diseases and medical conditions that are attributed to be possible causes of asterixis we have:

• Azotemia
• Subarachnoid hemorrhage, intracerebral hemorrhage, and subdural hematoma
• Congestive heart failure
• Wilson's disease
• Hypomagnesemia
• Hypokalemia
• Hypoglycemia

Treatment of asterixis

The treatment for this motor disorder is usually oriented to the solution and correction of its cause or that medical condition in which it has presented as a symptom.. If, for example, what has caused asterixis is a substance, either due to intoxication or as a side effect of a drug, the treatment would be simply recommending the suspension of the taking of that substance or modifying the dose.

However, if what has caused these tremors is a more serious medical condition, such as liver, kidney or pulmonary or cerebral hemorrhage, the treatment will depend on the severity in which the affected organ is and the possibilities of being able to to intervene. The use of antimyoclonic drugs is not recommended in patients with asterixis as these drugs are known to worsen symptoms rather than treat them.

In the event that asterixis is caused by end-stage kidney disease, dialysis is recommended as it can help with filtering toxic products from the blood and reduce the symptoms, although this method is inefficient in cases where the disease is due to a liver disorder, being necessary in these cases a liver transplant.