Altered Mental Status in the Emergency Department

Austin T. Smith, MD; Jin H. Han, MD, MSc


Semin Neurol. 2019;39(1):5-19. 

In This Article

Abstract and Introduction


Altered mental status is an umbrella term that covers a broad spectrum of disease processes that vary greatly in chronicity and severity. Causes can be a primary neurologic insult or a result of a systemic illness resulting in end-organ dysfunction of the brain. Acute changes in mental status are more likely than chronic changes to be immediately life-threatening and are therefore the focus of this review. Given the potential time-sensitive nature, acute changes in mental status must be addressed immediately and with urgency. We recommend a primary survey followed by a secondary survey with special attention to immediate life-threatening reversible causes. We then recommend a systems-based approach searching for any other life-threatening or reversible causes. Because the differential for altered mental status is broad, a comprehensive emergency department evaluation including a detailed history and physical exam as well as laboratory and radiographic testing is needed.


"Altered mental status" (AMS) describes any change in a patient's baseline mental status. This term, however, is vague and has several synonyms, including confusion, "not acting right," altered behavior, generalized weakness, lethargy, agitation, psychosis, disorientation, inappropriate behavior, inattention, and hallucinations.[1] AMS covers a broad spectrum of illnesses ranging in acuity and severity. It is a rather common chief complaint; up to 5 to 10% of emergency department (ED) patients present with AMS, with rates of approximately 40% in the elderly population.[2–5]

Changes in mental status have variable time courses and degrees of severity. Acute changes (minutes to days) are usually secondary to delirium, stupor, and coma, which are considered forms of acute brain failure.[6] These acute changes in mental status can be life-threatening. It can be caused by a primary neurologic emergency, but more often than not, these changes are the sequelae of an underlying acute medical illness (secondary). In general, the more acute and significant the change in mental status is, the more likely it is to be life-threatening.[7] Chronic (months to years) changes in mental status (e.g., dementia) are unlikely to be immediately life-threatening.[7] For these reasons, acute changes in mental status will be the focus of this review.

The ED must be adept in evaluating and managing patients with acute alterations in mental status. Because acute changes in mental status are potentially life-threatening, its primary goal is to rapidly identify those who are critically ill, efficiently diagnose the underlying etiology, and promptly initiate lifesaving therapies. This review will discuss the causes of AMS, the mental status assessment of the patient with AMS, as well as the appropriate diagnostic workup and treatment. Of all the forms of AMS, delirium is probably the most well studied and will be the focus of this review. However, the concepts pertinent to delirium can be generalized to stupor and coma, because there is significant overlap.