Initial Workup for Altered Mental Status
The initial workup for a patient presenting with altered mental status should include airway protection as the first priority, followed by a comprehensive metabolic laboratory assessment, and head CT without contrast as first-line neuroimaging. 1
Initial Assessment and Stabilization
- Airway protection is the first priority to prevent aspiration, with transfer to a monitored setting if necessary 1
- Assess mental status severity using validated scales such as the Glasgow Coma Scale to objectively quantify impairment 1, 2
- Evaluate for focal neurological deficits, which significantly increase the likelihood of intracranial pathology requiring immediate neuroimaging 2
- Document vital signs, as abnormalities may indicate specific etiologies (fever suggesting infection, hypotension suggesting shock) 2
- Obtain comprehensive medication, drug, and alcohol history to identify potential toxicologic causes 2
Laboratory Investigations
- Obtain metabolic laboratory assessment including complete blood count, comprehensive metabolic panel, electrolytes, renal and liver function tests 1, 2
- Include blood glucose testing as hypoglycemia is a rapidly reversible cause of altered mental status 2
- Perform toxicology screens when substance use is suspected 2
- Note that history and physical examination have 94% sensitivity for identifying medical conditions, while laboratory studies alone have only 20% sensitivity 3
- Most abnormal laboratory results can be predicted from a careful history and physical examination 3
Neuroimaging
- Head CT without contrast is usually appropriate as first-line neuroimaging for patients with first episode of altered mental status, focal neurological deficits, seizures, increased risk for intracranial bleeding, or hypertensive emergency 1, 2
- Brain MRI may be appropriate when CT is negative but clinical suspicion for intracranial pathology remains high 1, 2
- The yield of acute contributory findings on CT ranges from 2% to 45% based on trial design and inclusion criteria 3
- Risk factors associated with intracranial findings include history of trauma or falls, hypertension, anticoagulant use, headache, nausea or vomiting, older age, impaired consciousness, neurologic deficit, and history of malignancy 3
Common Etiologies to Consider
- Neurological causes (intracranial mass, encephalitis, meningitis) account for approximately 30-35% of cases 2, 4
- Toxicologic/Pharmacologic causes (medication side effects, alcohol intoxication, illicit drug use) account for 20-25% of cases 2, 4
- Metabolic/Systemic causes (hypoglycemia, hyperglycemia, electrolyte abnormalities, hepatic encephalopathy, uremia) account for 15-20% of cases 2
- Infectious causes (sepsis, urinary tract infection, pneumonia, meningitis) account for 9-18% of cases 2, 5
- Endocrine/metabolic causes account for 7.9% of cases 4
Special Considerations
- In patients with cirrhosis, hepatic encephalopathy is a common cause of altered mental status but remains a diagnosis of exclusion 1, 2
- For patients with known intracranial pathology and worsening mental status, neuroimaging should be performed to assess for progression 2
- In elderly patients, delirium is often multifactorial and carries higher mortality 1, 2
- Nonconvulsive seizures may be a cause of otherwise unexplained altered mental status, requiring EEG for diagnosis 6
- Consider autoimmune encephalitis in patients with unexplained encephalitis, which requires specific antibody testing 6
Pitfalls to Avoid
- Attributing altered mental status solely to psychiatric causes without adequate medical workup 1, 2
- Failing to consider multiple concurrent etiologies, especially in elderly patients 2
- Relying on ammonia levels alone to diagnose hepatic encephalopathy in cirrhotic patients 1, 2
- Delaying empiric treatment while awaiting diagnostic results in potentially life-threatening conditions 1, 2
- Overlooking the high mortality rate associated with altered mental status, which can be as high as 8.1% 4