Encephalopathy refers to any disease of the brain that alters brain function or structure. Infections with bacteria, viruses or a protein called a prion that had become abnormal are among the many causes of this type of illness.

Specific forms of encephalopathy include:

• Hepatic encephalopathy. Occurs when the liver stops functioning properly and fails to metabolize or detoxify substances in the body.
  
  
• Transmissible spongiform encephalopathies (TSEs). These rare and deadly degenerative brain disorders are marked by tiny holes that make the brain appear “spongy.”

The main symptom of encephalopathy is an altered mental state. People may experience progressive memory loss and a decline in cognitive ability. They may become confused, disoriented and forgetful. Subtle personality changes may emerge, and patients may experience lethargy, seizures, inability to concentrate and progressive loss of consciousness.

In diagnosing encephalopathy, tests may be performed to help identify the specific underlying cause of the illness. These include blood tests, electroencephalograms (measures of brain’s electrical activity) and imaging studies such as magnetic resonance imaging (MRI).