Hepatic encephalopathy (HE) is an altered level of consciousness as a result of liver failure. Its onset may be gradual or sudden. Other symptoms may include movement problems, changes in mood, or changes in personality. In the advanced stages it can result in a coma. Hepatic encephalopathy can occur in those with acute or chronic liver disease. Episodes can be triggered by infections, GI bleeding, constipation, electrolyte problems, or certain medications. The underlying mechanism is believed to involve the buildup of ammonia in the blood, a substance that is normally removed by the liver. The diagnosis is typically based on symptoms after ruling out other potential causes. It may be supported by blood ammonia levels, an electroencephalogram, or a CT scan of the brain. Hepatic encephalopathy is possibly reversible with treatment. This typically involves supportive care and addressing the triggers of the event. Lactulose is frequently used to decrease ammonia levels. Certain antibiotics (such as rifaximin) and probiotics are other potential options. A liver transplant may improve outcomes in those with severe disease. More than 40% of people with cirrhosis develop hepatic encephalopathy. More than half of those with cirrhosis and significant HE live less than a year. In those who are able to get a liver transplant, the risk of death is less than 30% over the subsequent five years. The condition has been described since at least 1860. Signs and symptoms The mildest form of hepatic encephalopathy is difficult to detect clinically, but may be demonstrated on neuropsychological testing. It is experienced as forgetfulness, mild confusion, and irritability. The first stage of hepatic encephalopathy is characterised by an inverted sleep-wake pattern (sleeping by day, being awake at night). The second stage is marked by lethargy and personality changes. The third stage is marked by worsened confusion. The fourth stage is marked by a progression to coma. More severe forms of hepatic encephalopathy lead to a worsening level of consciousness, from lethargy to somnolence and eventually coma. In the intermediate stages, a characteristic jerking movement of the limbs is observed (asterixis, "liver flap" due to its flapping character); this disappears as the somnolence worsens. There is disorientation and amnesia, and uninhibited behaviour may occur. In the third stage, neurological examination may reveal clonus and positive Babinski sign. Coma and seizures represent the most advanced stage; cerebral edema (swelling of the brain tissue) leads to death. Encephalopathy often occurs together