The asterixis is a clinical sign indicating a lapse in the tonic innervation and is usually manifested by an involuntary tremor in the joints of the wrist, metacarpophalangeal and hip that resembles the flapping wings. It usually affects both hands, although sometimes it affects one in particular.
The tremor or muscle movements are involuntary, and generally appear when the arms are extended and the wrists flexed. People with this disorder have a hard time keeping the affected body part stable for long.
Asterixis is considered a type of negative myoclonus that occurs when the agonist muscles temporarily lose their muscle tone, causing a visible involuntary tremor.
In the vast majority of cases the condition develops in the hands; however, it is not exclusive and can be observed in other parts of the human body. Involuntary fluttering of the eyelids, trembling of the lips or tongue, and movement of the ankles and feet are also signs of asterixis.
Types
The reasons for asterixis are often associated with different conditions, from diseased organs to lesions in the brain. Taking this into account, asterixis is classified into two types:
Bilateral
The most common causes of bilateral asterixis are metabolic encephalopathies, especially liver and kidney. This means that an imbalance in electrolytes and chemicals affects the functioning of the brain, causing asterixis.
The rationale behind this type of asterixis lies in the role of the liver and kidneys in the body's metabolism, since these organs are responsible for eliminating toxic waste from the body, either by metabolism and inactivation or by excretion.
One of the main wastes produced by the body's metabolism is nitrogen; This, not being able to be eliminated properly, is incorporated to other proteins in the blood and acts as an aberrant neurotransmitter, triggering the peripheral tremor so characteristic of asterixis.
Also heart and respiratory diseases, as well as drug intoxication, are known to cause bilateral asterixis.
Unilateral
It is caused mainly by focal brain lesions in the genu and anterior portion of the internal capsule or the ventrolateral thalamus.
This is due to the fact that through this region nerve fibers come out directly from the cerebral cortex with motor action. Lesions in the midbrain, parietal cortex, and medial frontal cortex are also responsible for unilateral asterixis.
Symptoms
Asterixis is a motor disorder. The main symptom of this condition is quite easy to recognize: involuntary shaking or fluttering in the hands and wrists.
The tremor is usually an irregular jerky movement with a frequency of 3 to 5 Hz, which occurs when the person stretches the arms and flexes the wrists. That is, it is difficult for the person to maintain a fixed position.
Asterixis can also cause pain in the joints and muscles, as well as weakness and discomfort. Other parts of the body also often have a motor disorder, such as the jaw, tongue, neck and eyelids.
A person with asterixis may show other symptoms depending on the cause of the condition. For example, if the patient has bilateral asterixis caused by metabolic encephalopathy, they will present with very florid symptoms.
In this case, altered mental status is the most prominent symptom, since there are aberrant neurotransmitters circulating in the blood that also affect the brain and, therefore, affect the person's behavior (this clinical finding is known as delirium).
You may also have yellowing of the skin or jaundice from the accumulation of bilirubin. Likewise, you may suffer from swelling or edema of the feet, diarrhea and cramps due to an imbalance of electrolytes, and even bleeding manifested as bloody stools, bleeding gums, blood in the urine or vomiting with blood (hematemesis).
Causes
Internal malfunction, severe enough for the brain to have mixed messages, is the indication of involuntary muscles. This is what happens when you suffer from asterixis.
Hepatic encephalopathy is seen in patients with cirrhosis. This produces brain deterioration that causes various disorders, such as mild personality changes, confusion, and often causes tremors that can lead to asterixis.
Severe respiratory failure is caused when the lungs have a hard time absorbing oxygen and releasing carbon dioxide, causing headaches and loss of reflexes. Upon reaching a critical point, it could cause asterixis and lead the patient into a coma.
Uremic syndrome is a kidney disorder that occurs when the kidneys are malfunctioning. As it progresses, it can cause asterixis as the person gradually loses control of motor movement.
Even substances such as alcohol and medications such as barbiturates, lithium, carbamazepine, gabapentin, valproate, ceftazidime, and metoclopramide can cause asterixis as a side effect.
Other known common causes include the following:
-Azotemia.
-Brain problems such as subarachnoid hemorrhage, intracerebral hemorrhage and subdural hematoma.
-Congestive heart failure.
-Hypomagnesemia.
-Hypoglycemia.
-Hypokalemia.
-Wilson disease.
Treatments
Treatment of asterixis usually goes hand in hand with the cause of the condition and will depend on how much damage it has caused.
If medication is found to be the cause of asterixis, treatment is as simple as recommending discontinuation of medication or modifying the dose.
However, if the cause is a more serious underlying condition - such as liver, lung or kidney disease - treatment will depend on the severity of the affected organ.
Knowing that a person has asterixis should avoid antimyoclonic medications, as they are known to aggravate symptoms rather than treat them.
Dialysis can help with end-stage kidney disease, as this process filters toxic products from the blood; however, it is inefficient in cases of liver disease, so these patients must opt for a transplant.
References
- What is Asterixis, Know its Causes, Symptoms, Treatment, Pathophysiology, Risk Factors, Sf, ePain Assist: epainassist.com
- Asterixis: Types, causes, symptoms, risk factors, diagnosis, and treatment, (2018), Bel Marra Health: belmarrahealth.com
- Brent Chittenden, (2017), Understanding Asterixis: Causes, Symptoms, Diagnosis, and Treatments, Doctors Health Press: doctorshealthpress.com
- Miljan Krcobic, (2017), Define Asterixis and its causes, types, symptoms, diagnostic test, treatment and pictures, Disease Definition: diseasedefinition.info
- Asterixis, (2011), Science Direct: sciencedirect.com
- Aric Parnes, Sf, Asterixis: tcd.ie