When is a diagnosis of altered mental status appropriate in a patient?

When to Use the Diagnosis of Altered Mental Status

Altered mental status should never be used as a final diagnosis—it is a descriptive term for symptoms requiring urgent investigation to identify the underlying treatable cause. 1

Understanding AMS as a Symptom, Not a Diagnosis

The American College of Radiology explicitly states that AMS is not a diagnosis but rather a term describing symptoms of acute or chronic disordered mentation. 1 These symptoms include:

• Confusion, disorientation, and inattention 1
• Lethargy, drowsiness, somnolence, or unresponsiveness 1
• Agitation and altered behavior 1
• Hallucinations, delusions, and psychosis 1

When AMS is Appropriate as an Initial Presenting Complaint

Use "altered mental status" only as an initial chief complaint or triage descriptor while actively pursuing the underlying diagnosis. 1 This is appropriate in the following clinical contexts:

Emergency Department Presentation

• AMS accounts for 4-10% of ED chief complaints and serves as a starting point for evaluation 1, 2
• It signals the need for expedited workup to exclude intracranial processes requiring intervention 1
• Overall mortality is 8.1%, significantly higher in elderly patients, making prompt etiologic diagnosis critical 1, 2

High-Risk Scenarios Requiring Immediate Investigation

Mortality doubles when the underlying cause is missed, making AMS a medical emergency. 3, 4, 5 Use AMS as the presenting problem when:

• Acute temporal course (symptoms developing over minutes to days) 3, 4
• Fluctuating consciousness throughout the day with lucid intervals 3, 5
• Elderly patients with multiple potential precipitants 3, 4
• Unclear etiology requiring systematic evaluation 1

The Diagnostic Imperative: Moving Beyond AMS

Your primary obligation is to identify the specific underlying cause, not to document "altered mental status" as the final diagnosis. 1, 5 The most common etiologies include:

Primary Categories (in order of frequency)

• Neurological causes (35%): Stroke, seizures, intracranial hemorrhage, subdural hematoma 5, 2, 6
• Pharmacological/toxicological (23%): Polypharmacy, anticholinergics, sedatives, substance withdrawal 4, 5, 2
• Systemic/organic dysfunction (14.5%): Hypoxia, cardiac causes, hepatic encephalopathy 5, 2
• Infectious (9-18%): UTI (most common in elderly), pneumonia, meningitis/encephalitis 3, 5, 2
• Endocrine/metabolic (8%): Hypoglycemia, hyperglycemia, electrolyte abnormalities, thyroid disorders 3, 4, 5
• Psychiatric (4%): New-onset psychosis, severe depression, catatonia 1, 5

Delirium: The Most Common Specific Diagnosis

When AMS presents with inattention and fluctuating course, the specific diagnosis is delirium, not "altered mental status." 3, 5 Delirium:

• Occurs in 10-31% at hospital admission and develops in up to 56% of hospitalized patients 5
• Represents a medical emergency with doubled mortality when missed 3, 4, 5
• Requires identification of precipitating factors (medical condition, intoxication, withdrawal) 5
• Should be diagnosed using validated tools like the Confusion Assessment Method (CAM) 4

Critical Pitfalls to Avoid

Never use "altered mental status" as a discharge diagnosis without identifying the underlying cause. 5 Specific errors include:

• Attributing AMS solely to psychiatric causes without adequate medical workup 5
• Assuming dementia or baseline cognitive impairment explains acute changes 3, 4
• Missing multiple coexisting etiologies, particularly in elderly and critically ill patients 5
• Delaying empiric treatment for life-threatening reversible causes while pursuing diagnosis 5

When Neuroimaging is Indicated

The American College of Radiology provides clear guidance on when imaging is "usually appropriate" during AMS evaluation: 1

• First episode of altered mental status 5
• Focal neurological signs or deficits 1, 4
• History of trauma or anticoagulant use 3, 4
• Significantly elevated blood pressure suggesting hypertensive emergency 4
• Lower Glasgow Coma Scale score 4

However, diagnostic yield of neuroimaging is only 5-6.4% without focal deficits or trauma signs, emphasizing that most AMS has non-neurological causes. 3

The Bottom Line for Clinical Practice

Use "altered mental status" only as a temporary descriptor during active evaluation—your documentation should reflect the specific underlying diagnosis (delirium due to UTI, encephalopathy from hyperglycemia, etc.) before patient disposition. 1, 5 This approach ensures appropriate treatment, accurate prognostication, and proper resource allocation for this high-mortality presentation. 2, 6