Asterixis


Asterixis

Description, Causes and Risk Factors:

Involuntary jerking movements, especially in the hands, best elicited by having the patient extend the arms, dorsiflex the wrists, and spread the fingers; due to arrhythmic lapses of sustained posture; seen primarily with various metabolic and toxic encephalopathies, especially hepatic encephalopathy.

asterixis

This condition is sometimes called liver flap because it can indicate liver damage or damage to the brain caused by liver failure. The liver might fail to filter certain chemicals from the blood, which in turn can cause brain damage called hepatic encephalopathy. Liver flap can be seen in people who have untreated liver failure, especially cirrhosis of the liver. The wrist tremor in patients who have this kind of liver damage or associated brain damage might be accompanied by an appearance of sleepiness or stupor.

Usually there are brief, arrhythmic interruptions of sustained voluntary muscle contraction causing brief lapses of posture, with a frequency of 3-5 Hz. It is bilateral, but may be asymmetric.

The exact mechanism by which asterixis occurs remains unknown. A leading theory suggests interruption of the posture pathway in the rostral reticular formation and abnormal joint proprioception. The lapse of posture has been termed "negative clonus" because during tonic muscle contraction (i.e. posture) a short EMG silent period precedes the tremor. In essence, the patient struggles to maintain posture while posture control repetitively vanishes.

Types may include:

    Unilateral asterixis: These are most commonly due to focal brain lesions in the genu and anterior portion of the internal capsule or ventrolateral thalamus. Lesions in the midbrain, parietal cortex, and medial frontal cortex may also cause unilateral asterixis.

  • Bilateral asterixis: Metabolic encephalopathies, especially hepatic and renal, are the most common causes of bilateral asterixis. Those caused specifically by hepatic failure are known as "liver (or hepatic) flap." Other causes of asterixis include cardiac and respiratory disease, electrolyte abnormalities and drug intoxication. Electrolyte abnormalities known to cause asterixis include hypoglycaemia, hypokalaemia and hypomagnesaemia. Drug intoxications include barbiturate intoxication, alcoholism, phenytoin intoxication ("phenytoin flap") and primidone intoxication. Wilson's disease and focal brain lesions in the rostral midbrain tegmentum may also cause asterixis.

Asterixis might also be a sign of too many nitrogen compounds in the blood, which can be caused by problems with the kidneys. This is called azotemia. The kidneys have trouble filtering out nitrogen-based compounds, either because there is some condition keeping the kidneys from getting enough blood to filter or because there is something wrong with the kidneys that keep them from properly filtering the blood despite a normal supply of it. Azotemia might also be a result of abnormal urine output.

Symptoms:

Asterixis usually causes hand tremors which is occur in both wrists which include some symptoms like irregular movement at the wrist jerky pain in joints, arm weakness. Asterixis is describing a motor disturbance which involves the tongue, jaw, eyelids, neck and arms. Other symptoms are brain damage and also caused by drugs.Sometime it occurs usually dosage of drugs. So, try to reduce the dosage of drugs take medicine after prescribed by doctor.

Diagnosis:

The diagnosis may include the following test:

Extend the arms, spread the fingers, dorsiflex the wrist and observe for the abnormal “flapping” tremor at the wrist. If not immediately apparent, this tremor may be accentuated by asking the patient to keep the arms straight while the examiner gently hyperextends the patient's wrist with a sweeping motion.

An alternate method of testing for asterixis involves having the patient relax his legs while he lies supine with his knees bent. The feet should be kept flat on the table and as the legs fall to the sides, watch for flapping of the legs at the hip joint. This repetitively brings the knees back together.

Treatment:

Treatment of asterixis is indirect, consisting of treatment of the damage done to the liver, kidneys or brain and nervous system. Success depends on whether the underlying damage is reversible. Healthcare practitioners use blood tests to determine the cause of the wrist tremors and proceed accordingly.

Lowering the levels of ammonia caused by hepatic encephalopathy, nitrogen-based compounds caused by azotemia and copper levels caused by Wilson's disease might stop the wrist tremor. It might also help to take certain drugs that act on the brain, such as clonazepam. Whatever the cause, asterixis might be a sign that the underlying condition has become serious, and immediate action is necessary.

NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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