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Updated 25 July 2012

Encephalopathy

Encephalopathy is a term given to any of a number of diseases which affect the functioning of the brain.

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Definition

Encephalopathy is the general term used for any condition that affects the overall functioning of the brain, leading to a change in the level of consciousness and alteration of the higher mental functions. Symptoms range from slight changes in personal manner and alertness, to confusion, lethargy and even coma and death. Lack of oxygen to the brain, severe infections, intoxication with drugs or alcohol, and liver and kidney failure are all common causes of encephalopathy.

Cause

As has been mentioned, a wide variety of conditions may give rise to encephalopathy, particularly when they are advanced and severe.

Hypoxic encephalopathy refers to brain damage that is the result of a lack of oxygen to the brain. Cardiac arrest is the commonest situation where this form of injury occurs, but drowning, carbon monoxide poisoning, severe haemorrhage, low blood pressure (shock), and respiratory failure can all produce similar effects. When the heart stops beating, irreversible brain damage occurs after about 2 minutes.

Liver and kidney failure from any cause result in encephalopathy when severe. In both cases, the effects on the brain function are probably a result of accumulated waste products that are not effectively cleared from the body by the diseased organs. Liver failure is frequently caused by many years of excessive alcohol use, or in certain forms of hepatitis.

Encephalopathy may develop after a gastrointestinal haemorrhage or intercurrent infection, and is managed by a low protein diet, laxatives and antibiotics, to minimize the load placed on the liver. Kidney failure producing uremic encephalopathy is generally treated only with dialysis or transplantation of the kidney.

Severe infections, particularly those affecting the brain (encephalitis) and its surrounding coverings (meningitis) may result in encephalopathy. If antibiotics are administered in time, full recovery is possible, but severe infections particularly where the brain is involved directly, may cause lasting damage.

Alcohol and drug overdose are usually reversible, but may result in permanent brain damage.

Symptoms and signs

Encephalopathy caused by lack of oxygen to the brain

Mild hypoxia causes inattentiveness, impaired judgment and lack of motor co-ordination, but has no lasting effects. With severe hypoxia or anoxia, which occurs with cardiac arrest, consciousness is lost within seconds. However, recovery will be complete if breathing, oxygenation of the blood and heart action are restored within two to five minutes. If anoxia persists for longer than this, there will be permanent and severe brain damage.

There can be imperceptible blood pressure or slight heart action which can maintain the circulation to some extent. This accounts for reports of people who have apparently recovered completely after appearing to be anoxic for eight to 10 minutes or more.

Anoxia which is extreme and sustained causes brain death.

Hepatic encephalopathy

The symptoms and signs of hepatic encephalopathy are extremely variable. Almost any type of nervous system abnormality may be seen. These include personality changes and impaired consciousness. A characteristic early sign (called constructional apraxia) is the inability to reproduce simple designs, for example a star.

Uraemic encephalopathy

The early signs of uraemic encephalopathy are apathy, fatigue, inattentiveness and irritability. Later, confusion, hallucinations, stupor and disturbances in taste, smell and hearing occur.

The later symptoms are almost always associated with twitching muscles and jerking limbs. The person may suffer convulsions.

Diagnosis

Diagnosis of encephalopathy due to hypoxia or anoxia depends on knowing that the person suffered from some event which led to hypoxia or anoxia. Evidence for this comes from measuring the level of blood oxygen in the arteries.

The diagnosis of hepatic encephalopathy depends on the presence of four major factors:

  • Acute or chronic liver disease.
  • Disturbances of awareness and thinking which may progress from forgetfulness and confusion to stupor and finally coma.
  • Shifting combinations of signs of nervous system damage.
  • A characteristic pattern shown when the brain waves are measured using an encephalogram.

Diagnosis of uraemic encephalopathy depends on the presence of clinical symptoms of the condition together with knowing that the person is suffering from severe kidney failure.

Treatment

The treatment of anoxic or hypoxic encephalopathy is aimed at preventing further damage by restoring full levels of oxygen to the brain as soon as possible - by restoring circulation or breathing, or both.

It is essential to treat hepatic encephalopathy as early as possible to prevent long-term damage. Specific treatment is aimed at the elimination or treatment of the precipitating factors, such as bleeding, and lowering blood ammonia and other toxin levels by decreasing the absorption of protein from the gut. This also involves clearing any blood present in the gut using laxatives and enemas.

Protein should be excluded from the diet and constipation avoided. The absorption of ammonia can be decreased by giving lactulose.

If uraemic encephalopathy is caused by progressive kidney failure, then dialysis or transplant are the only methods of treatment.

When to call the doctor

If anyone around you suffers from an event which can result in hypoxia, such as a heart attack, a doctor should be called immediately, or the person taken to the nearest emergency centre.

If someone in your family is known to have chronic liver disease and their behaviour starts to change or they become confused, they should see a doctor immediately.

Reviewed by Dr Andrew Rose-Innes, Yale University School of Medicine, 2007

 
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