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

What is asterixis? Let's see what this motor disorder consists of, and its types.

Asterixis is a motor alteration present in various hepatic, renal, respiratory, cardiac and cerebral disorders.

It manifests itself in the form of tremors, similar to those of a bird flapping its wings, and can be caused by many different causes. Let's delve further into the characteristics of this clinical sign.

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 in the involuntary occurrence of rhythmic interruptions of a muscle contraction.It is usually manifested by tremors in the wrist, metacarpophalangeal and hip joints. This problem usually affects both hands, although it may also affect only one hand in particular.

This problem is also called liver flapping 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 are flexed. Patients with this medical condition find it difficult to keep the affected body part stable..

Despite having the appearance of a tremor and often being referred to as such, asterixis is not considered a tremor in the strictest sense of the word, but rather repetitive contractions produced by repeated relaxations of the produced by repeated relaxations of the muscles engaged in spontaneous movements. However, when a patient with this motor disorder is seen, their physical behavior resembles that of a bird flapping its wings, which is why in everyday language they are called tremors.

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

Associated symptoms

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

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

A patient suffering from asterixis may show other symptoms depending on the cause of his or her motor disorder. An example of this is bilateral asterixis caused by a metabolic encephalopathy which usually has very developed symptoms. In this case this condition may also be accompanied by a mental state due to irregular levels of neurotransmitters circulating in the Blood and causing bizarre behavior.

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

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 mainly classified into two types.

Bilateral

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

Alterations in the kidneys and liver are especially harmful to the organism in general and to the brain in particular, because when they do not work properly, imbalances in the levels of electrolytes and other chemical substances in the blood are produced. When organic homeostasis is lost, both the brain and other organs cease to function correctly 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 wastes from the body, either by metabolizing and inactivating them or directly eliminating them from the body through excretion.

One of the main waste products of the body's metabolism is nitrogen.. This substance, when not properly eliminated, ends up being incorporated into other proteins in the blood and converts them into aberrant neurotransmitters, which cause the peripheral tremors so characteristic of asterixis.

It should be said that alterations in the liver and kidneys are not the only potential causes behind a case of asterixis. Heart and respiratory diseases as well as substance intoxication may also be behind a case of this type of asterixis.

2. Unilateral

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

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

Related pathologies

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

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

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

We can also speak of uremic syndrome, a renal disorder that occurs when there is a malfunction of the kidneys. As this medical condition worsens, it can result in asterixis as the person progressively loses control of voluntary motor movement.

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

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

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

Treatment of asterixis

Treatment for this motor disorder is usually aimed at resolving and correcting 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 by intoxication or as a side effect of a drug, the treatment would be simply to recommend the suspension of taking that substance or modify the doses.

However, if a more serious medical condition, such as liver, kidney or lung disorders or a brain hemorrhage, has caused the tremors, treatment will depend on the severity of the affected organ and the possibilities of intervention. The use of antimyoclonic drugs in patients suffering from asterixis is not recommended since these drugs are known to worsen symptoms rather than treat them.

In case asterixis is caused by end-stage renal disease, dialysis is recommended since it may can help with the filtering of 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, in which case a liver transplant is necessary.