Altered Mental Status Differential Diagnoses

Introduction to Altered Mental Status

The American College of Radiology suggests that the most common differential diagnoses for altered mental status include underlying medical conditions, substance use/intoxication/withdrawal, mental disorders, delirium, and primary neurologic insults, with delirium being the most frequent presentation in older patients presenting to the emergency department 1, 2

Delirium represents a medical emergency and is the most common presentation in elderly patients with altered mental status, occurring in 10-31% at admission and developing in up to 56% of hospitalized patients, according to the American College of Radiology 1, 5
The cardinal feature of delirium is inattention with a fluctuating course throughout the day with lucid intervals, as stated by the American College of Radiology 2, 5
Precipitating factors for delirium include another medical condition, intoxication, or withdrawal, as noted by the American College of Radiology 5
The mortality risk is twice as high if the diagnosis of delirium is missed, with an overall mortality of 8.1% in altered mental status patients, which is significantly higher in the elderly, according to the American College of Radiology 5, 6

New-onset psychosis differs from other altered mental status presentations because the level of consciousness and awareness remain intact, as stated by the American College of Radiology 2
Primary psychosis is related to underlying psychiatric disorders, while secondary psychosis is directly related to medical causes, including endocrine disorders, autoimmune diseases, neoplasms, and neurologic disorders, as noted by the American College of Radiology 2, 6

In patients with cirrhosis, hepatic encephalopathy is a common cause of altered mental status but remains a diagnosis of exclusion after ruling out other etiologies, according to Hepatology 4
Important differentials in cirrhotic patients include alcohol intoxication and withdrawal, drug-related causes, infections, diabetic ketoacidosis, and electrolyte disorders, as stated by Hepatology 4

Conditions requiring urgent neuroimaging include first episode of altered mental status, focal neurological signs or deficits, seizures, increased risk for intracranial bleeding, and hypertensive emergency, as suggested by Praxis Medical Insights and Hepatology 4, 7
Life-threatening reversible causes that require immediate intervention include hypertensive emergency, meningitis/encephalitis, and severe electrolyte abnormalities, according to Praxis Medical Insights and Hepatology 4, 7

Never attribute altered mental status solely to psychiatric causes without adequate medical workup, as this can miss life-threatening conditions, as warned by the American College of Radiology 6
Do not rely on ammonia levels alone to diagnose hepatic encephalopathy in cirrhotic patients, as a low ammonia level should prompt investigation of other etiologies, according to Hepatology 4
Avoid delaying empiric treatment while awaiting diagnostic results in potentially life-threatening conditions, as advised by Praxis Medical Insights 7
Do not miss delirium in elderly patients, as mortality doubles when diagnosis is missed, as stated by the American College of Radiology 5
Remember that multiple etiologies can coexist, particularly in elderly and critically ill patients, as noted by Hepatology 4