Most patients who are admitted to the hospital with the symptom of mental status alteration actually have encephalopathy as the cause.

How many patients who are admitted to the hospital have, as one of their medical problems, an altered mental status? Many times this is the principal reason families bring them to the office or hospital in the first place, and expect them to be admitted!

A major difficulty in translating the severity of illness and complexity of patient care into correct ICD-9 codes is that, for coding purposes, “mental status alteration” is classified as a non-specific symptom. Usually, symptoms are not even coded at all, thus the clinical challenges posed by altered mental status—and the resources used—go unrecognized.


The official coding guidelines recommend avoiding symptoms as diagnoses and encourage physicians to identify the underlying causes or conditions. Most patients who are admitted to the hospital with the symptom of mental status alteration actually have an encephalopathy as the cause.

Defining encephalopathy

While there are no official or specific textbook definitions, encephalopathy can be accurately described as a generalized, or global, alteration in all aspects of brain function (communication, memory, speech, orientation, behavior) due to a systemic underlying cause that is usually reversible. It is typically acute (or subacute) in onset and resolves when the underlying cause is corrected. Common causes of encephalopathy include fever, infection, dehydration, electrolyte imbalance, acidosis, organ failure, sepsis, hypoxia, drugs, poisons or toxins.

Types of encephalopathy

Toxic encephalopathy generally refers to the effects of drugs, toxins, poisons and medications. Metabolic is intended to describe encephalopathy due to such things as fever, dehydration, electrolyte imbalance, acidosis, infection and organ failure. Toxic-metabolic is sometimes used to describe the combination of toxic and metabolic effects. Septic encephalopathy is a term that describes brain dysfunction as a manifestation of severe sepsis. Uremic and hepatic encephalopathies are well-known clinical manifestations of renal and hepatic failure.

Encephalopathy vs. delirium

Making a clinical distinction between delirium and encephalopathy is very important but can be confusing. From a coding perspective, delirium is classified as a mental disorder or as a symptom; encephalopathy is recognized as a specific neurologic diagnosis that identifies toxic and metabolic states affecting the brain.

For precise documentation and correct coding, the diagnostic term encephalopathy is preferred for describing mental status alteration when due to toxic or metabolic causes. The term delirium is best reserved for psychiatric conditions unrelated to underlying systemic conditions.