Altered Mental Status in the Emergency Department

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

Disclosures

Semin Neurol. 2019;39(1):5-19. 

In This Article

Definitions

Coma, stupor, and delirium represent the broad spectrum of acute brain dysfunction (Figure 1) and are associated with impairment of consciousness. There are two inter-related domains of neurologic function that are related to consciousness: content and arousal.[8] The content of consciousness consists of cortex level functions such as orientation, perception, executive functions, and memory.[8] These processes are performed by widespread neuronal networks located in the cortical regions.[9] It can be assessed quickly by asking the patient orientation questions such as their name, the date, and where they physically are. Arousal is the patient's wakeful state and responsiveness to surrounding environment and stimuli. It is mediated by the reticular activating system functions, and dysfunction is described by terms such as lethargy, drowsiness, and somnolence.

Figure 1.

Spectrum of acute brain dysfunction based on the Richmond and Agitation Sedation Scale (RASS).23, 24 (Image courtesy of Vanderbilt University, Nashville, TN. Copyright 2012. Used with permission.)

A comatose patient is unresponsive to any stimuli. Stupor describes a state of arousal only with vigorous and continuous painful stimulation. Delirium describes an acute disturbance of consciousness that is accompanied by an acute loss of cognition that is not better explained by a preexisting neurocognitive disorder such as dementia.[10]Delirium is a highly heterogeneous syndrome and is frequently subtyped by its psychomotor activity.[11]

  1. Hypoactive delirium is characterized by psychomotor retardation, and patients can appear to be drowsy or somnolent. Because the clinical presentation of hypoactive delirium is subtle and often attributed to other etiologies such as depression or fatigue,[12,13] this subtype is often missed by clinicians.[14]

  2. Hyperactive delirium is characterized by a state of restlessness, agitation, or combativeness. This is the easiest to detect, but the least common subtype encountered in the ED.[15]

  3. Mixed-type delirium is a state that presents with features of both hyperactive and hypoactive delirium.

Though the subtypes are more commonly associated with certain etiologies, this is not absolute. The hypoactive subtype is more commonly associated with infection or metabolic causes, while alcohol or benzodiazepine withdrawal is more commonly associated with the hyperactive subtype.[16]

Dementia is a chronic form of AMS and is characterized by a gradual loss of cognition over a period of months to years. While dementia is not an emergency, there are a few reversible conditions associated with it that clinicians must be aware of. These include normal pressure hydrocephalus, hypothyroidism, vitamin B12 deficiency, and depression.

It is also important to note that dementia is an important predisposing factor to delirium, and patients can have both conditions concurrently.[17] Delirium and dementia's clinical features can overlap in patients with end-stage dementia or dementia with Lewy's bodies.[18,19] When these patients develop delirium, an acute change in mental status is still observed, and any preexisting abnormalities in cognition and level of consciousness will likely worsen.

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