Altered mental status versus delirium versus encephalopathy
As an example, let’s look at the difference in RW, LOS, and reimbursement in an otherwise identical patient based on documenting altered mental status (AMS), delirium, or encephalopathy. (see Table 1)
As one can see, RW, estimated LOS, and reimbursement would significantly increase for the patient with delirium (CC) or encephalopathy (MCC) versus AMS (no CC/MCC). A list of which diagnoses are considered CC’s versus MCC’s are on tables 6J and 6I, respectively, on the same Medicare website as table 5.
The difference between AMS, delirium, and encephalopathy
AMS is a sign/symptom complex similar to shortness of breath before an etiology is found. AMS can be the presenting symptom; when a specific etiology is found, however, a more specific diagnosis should be used such as delirium or encephalopathy.
Delirium, according to the DSM-5, is an acute change in the level of attention, cognition, or perception from baseline that developed over hours or days and tends to fluctuate during the course of a day. The change described is not better explained by a preexisting or evolving neurocognitive disorder and does not occur in the context of a severely reduced level of arousal, such as coma. There is evidence from the history, physical examination, or laboratory findings that the disturbance is a direct consequence of a general medical condition, substance intoxication or withdrawal, exposure to a toxin, or more than one cause.
The National Institute of Neurological Diseases and Stroke defines encephalopathy as “any diffuse disease of the brain that alters brain function or structure. Encephalopathy may be caused by an infectious agent, metabolic or mitochondrial dysfunction, brain tumor or increased intracranial pressure, prolonged exposure to toxic elements, chronic progressive trauma, poor nutrition, or lack of oxygen or blood flow to the brain. The hallmark of encephalopathy is an altered mental state.”
It is confusing since there is a lot of overlap in the definitions of delirium and encephalopathy. One way to tease this out conceptually is noting that delirium is listed under mental, behavioral, and neurodevelopmental disorders, while encephalopathy appears under disorders of the nervous system. One can think of delirium as more of a “mental/psychiatric” diagnosis, while encephalopathy is caused by more “medical” causes.
If a patient who is normally not altered presents with confusion because of an infection or metabolic derangement, one can diagnose and document the cause of an acute encephalopathy. However, let’s say a patient is admitted in the morning with an infection, is started on treatment, but is not initially confused. If he/she later becomes confused at night, one could err conservatively and document delirium caused by sundowning.
Differentiating delirium and encephalopathy can be especially difficult in patients who have dementia with episodic confusion when they present with an infection and confusion. If the confusion is within what family members/caretakers say is “normal,” then one shouldn’t document encephalopathy. As a provider, one shouldn’t focus on all the rules and exceptions, just document as specifically and accurately as possible and the coders should take care of the rest.