Assessment of altered mental status

Altered mental status (AMS) is a general term used to describe various disorders of mental functioning ranging from slight confusion to coma.[1]Han JH, Wilber ST. Altered mental status in older patients in the emergency department. Clin Geriatr Med. 2013 Feb;29(1):101-36. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3614410 http://www.ncbi.nlm.nih.gov/pubmed/23177603?tool=bestpractice.com Given the vagueness of the term, it is imperative to understand its key components before considering a differential diagnosis. Fundamentally, mental status is a combination of the patient's level of consciousness (i.e., attentiveness) and cognition (i.e., mental processes or thoughts); patients may have disorders of one or both.[2]Wilber ST, Ondrejka JE. Altered mental status and delirium. Emerg Med Clin North Am. 2016 Aug;34(3):649-65. http://www.ncbi.nlm.nih.gov/pubmed/27475019?tool=bestpractice.com For example, patients with meningitis may have impaired consciousness (i.e., altered sensorium, decreased attentiveness) with intact cognition, whereas patients with dementia may have a normal level of consciousness with impaired cognition. However, more frequently, patients exhibit altered levels of consciousness plus cognition: for example, with delirium, a relatively common and sometimes fatal cause of AMS.

Epidemiology

An observational study conducted in the accident and emergency department found that acutely altered mental status was the primary reason for the visit for about 1% of all adult patients and 2.4% of older adults.[3]Xiao HY, Wang YX, Xu TD, et al. Evaluation and treatment of altered mental status patients in the emergency department: life in the fast lane. World J Emerg Med. 2012;3(4):270-7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4129809 http://www.ncbi.nlm.nih.gov/pubmed/25215076?tool=bestpractice.com About 40% of patients were aged over 60 years. Thirty-five percent of cases had a neurological cause (e.g., stroke, traumatic brain injury, or seizures). Acute alcohol intoxication, infection, and metabolic abnormalities were other common causes of AMS.[3]Xiao HY, Wang YX, Xu TD, et al. Evaluation and treatment of altered mental status patients in the emergency department: life in the fast lane. World J Emerg Med. 2012;3(4):270-7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4129809 http://www.ncbi.nlm.nih.gov/pubmed/25215076?tool=bestpractice.com

Another observational study reported that over half of adults aged over 65 years with AMS had delirium. Mortality was almost 25%, and the mortality rate increased if AMS lasted longer than 3 days. In this group, infection and neurological disease were the most common aetiologies.[4]Aslaner MA, Boz M, Çelik A, et al. Etiologies and delirium rates of elderly ED patients with acutely altered mental status: a multicenter prospective study. Am J Emerg Med. 2017 Jan;35(1):71-6. http://www.ncbi.nlm.nih.gov/pubmed/27765479?tool=bestpractice.com

Levels of consciousness

Normal state of consciousness consists of either the state of attentiveness in which most people function while not asleep, or one of the recognised stages of normal sleep from which the person can be easily aroused. Abnormal state of consciousness is more difficult to categorise, and many terms are used. Some of the more common terms include:[5]Young J, Inouye SK. Delirium in older people. BMJ. 2007 Apr 21;334(7598):842-6. http://www.ncbi.nlm.nih.gov/pubmed/17446616?tool=bestpractice.com [6]Lehman RK, Mink J. Altered mental status. Clin Pediatr Emerg Med. 2008;9:68-75.

• Hyper-alert: heightened arousal with increased sensitivity to immediate surroundings. Hyper-alert patients can be verbally and physically threatening, restless, and/or aggressive.

• Confused: disorientated; bewildered, and having difficulty following commands.

• Delirious: disorientated; restless, hallucinating, sometimes delusional.

• Somnolent: sleepy, responding to stimuli only with incoherent mumbles or disorganised movements.

• Lethargic: reduced level of alertness with decreased interest in the surrounding environment.

• Obtunded: similar to lethargy; the patient has a lessened interest in the environment, has slowed responses to stimulation, and tends to sleep more than normal, with drowsiness in between sleep states.

• Stuporous: profoundly reduced alertness and requiring continuous noxious stimuli for arousal.

• Comatose: state of deep, unarousable, sustained unconsciousness.[6]Lehman RK, Mink J. Altered mental status. Clin Pediatr Emerg Med. 2008;9:68-75.