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Altered mental status can be defined as a change in a person’s level of consciousness or cognitive function [2]. Whether these changes occur over time or suddenly, disruption in normal brain function can cause a change in usual behavior that may not be noticeable to the patient (him or herself) but is often noticeable to others and a cause for concern. Friends, family members, or bystanders may then summon EMS.

AMS encompasses a collection of more specific neurologic problems. For example, a patient with AMS may have a change in consciousness, which is described as having two major components: arousal and content. A patient with a change in arousal (level of alertness) may range from unresponsive (comatose) to hyperalert and unable to focus on the examiner. On the other hand, a patient with a change in the content of his consciousness may have a normal level of alertness but may have a change in brain function that causes an inability to interact with his environment (e.g., an inability to interpret or form language) [2].

Assessing mental status is about determining what specific behaviors or actions (or lack thereof) of a patient are abnormal or different from that patient’s usual baseline brain function. The assessment should consider what deficits are present (i.e., alteration in alertness, content, or both) and the timing of those deficits. For example, two common states of altered mental status are delirium and dementia. Delirium is distinguished by its acute onset, and patients may wax and wane in level of arousal, attentiveness, and cognition. Dementia is characterized by a more gradual onset of diminished cognition with normal level of arousal and often decreased orientation.

Assessment of the AMS patient may be challenging due to the breadth of abnormalities that the term encompasses and because the AMS patient is impaired in his or her ability to participate in the history and exam. Common medical terms used to describe AMS, such as stuporous, obtunded, or confused may hold different meaning for different medical professionals. For this reason, they are best avoided. Family or bystanders may also describe vague symptoms, such as “he’s just not acting right,” or nonspecific concerns. Nonetheless, the EMS clinician can develop an effective differential diagnosis and treatment plan by determining a patient’s specific deficits and gaining an understanding of timing and specific possible causes via a thorough history and exam.