Hepatic encephalopathy is deterioration of brain function that occurs in people with severe liver disease because toxic substances normally removed by the liver build up in the blood and reach the brain.
Substances absorbed into the bloodstream from the intestine pass through the liver, where toxins are normally removed. Many of these toxins (such as ammonia) are normal breakdown products of the digestion of protein. In hepatic encephalopathy, toxins are not removed because liver function is impaired. Also, some toxins may completely bypass the liver through abnormal connections (called collateral vessels) that form between the portal venous system (which supplies blood to the liver) and the general circulation. These vessels form as a result of liver disease and portal hypertension (high blood pressure in the portal vein, which is the large vein that brings blood from the intestine to the liver).
A procedure used to treat portal hypertension (called portosystemic shunting) may also enable toxins to bypass the liver. Whatever the cause, the outcome is the same: Toxins can reach the brain and affect its function. Exactly which substances are toxic to the brain is not known. However, high levels of protein breakdown products in the blood, such as ammonia, appear to play a role.
In people with a long-standing (chronic) liver disorder, encephalopathy is usually triggered by an event such as
Symptoms are those of impaired brain function, especially reduced alertness and confusion. In the earliest stages, subtle changes appear in logical thinking, personality, and behavior. The person's mood may change, and judgment may be impaired. Normal sleep patterns may be disturbed. People may become depressed, anxious, or irritable. They may have trouble concentrating.
At any stage of encephalopathy, the person's breath may have a musty sweet odor.
As the disorder progresses, people cannot hold their hands steady when they stretch out their arms, resulting in a crude flapping motion of the hands (asterixis). Their muscles may jerk involuntarily or after people are exposed to a sudden noise, light, a movement, or another stimulus. This jerking is called myoclonus. Also, people usually become drowsy and confused, and movements and speech become sluggish. Disorientation is common. Less often, people with encephalopathy become agitated and excited. Eventually, as liver function continues to deteriorate, they may lose consciousness and lapse into a coma. Coma often leads to death, despite treatment.
Diagnosis is based mainly on symptoms, results of the examination, and response to treatment. Doctors ask about possible triggers for the encephalopathy (such as an infection or a drug) to identify possible causes. They do blood tests to identify triggers, particularly disorders that can be treated (such as infections or bleeding in the digestive tract), and to confirm the diagnosis. The ammonia level is also measured. The level is usually abnormally high (indicating liver malfunction), but measuring the level is not always a reliable way to diagnose encephalopathy.
Doctors may do mental status tests to check for the subtle changes that occur in the early stages of hepatic encephalopathy. Electroencephalography(EEG) may also be done. EEG can detect abnormalities in brain activity but cannot distinguish hepatic encephalopathy from other possible causes.
In older people, hepatic encephalopathy may be more difficult to recognize in its early stages because its initial symptoms (such as disturbed sleep patterns and mild confusion) may be attributed to dementia or erroneously labeled as delirium.
Doctors try to eliminate any triggers for the encephalopathy, such as an infection or a drug.
Doctors also try to eliminate toxic substances from the intestine because these substances can contribute to encephalopathy. They may use one or more of the following measures:
With treatment, hepatic encephalopathy is frequently reversible. In fact, complete recovery is possible, especially if the encephalopathy was triggered by a reversible cause. However, people with a chronic liver disorder are susceptible to future episodes of encephalopathy. Some require continuous treatment.