Initial Workup for Altered Mental Status

Clinical Assessment

The American College of Radiology recommends assessing mental status using validated scales such as the West Haven criteria or Glasgow Coma Scale to objectively quantify severity 1, 2
Evaluate for focal neurological deficits, which significantly increase the likelihood of intracranial pathology requiring immediate neuroimaging 3, 4
Document vital signs, as abnormalities may indicate specific etiologies, such as fever suggesting infection, or hypotension suggesting shock 5, 6
Obtain comprehensive medication, drug, and alcohol history to identify potential toxicologic causes 6, 7

Obtain metabolic laboratory assessment including complete blood count, comprehensive metabolic panel, and urinalysis 6, 7
Blood glucose, electrolytes, renal function, and liver function tests should be included in the metabolic laboratory assessment 1
Toxicology screens should be performed when substance use is suspected 6, 7
Routine ammonia level testing is not recommended in patients with cirrhosis and altered mental status, as levels are variable and may be elevated in non-hepatic encephalopathy conditions 1

Head CT without contrast is usually appropriate as first-line neuroimaging for patients with first episode of altered mental status, focal neurological deficits, seizures, or new focal neurological signs 1, 3, 4
Brain MRI may be appropriate when CT is negative but clinical suspicion for intracranial pathology remains high, or when inflammatory conditions, encephalitis, or subtle vascular pathologies are suspected 4, 8, 9

Neurological causes, such as intracranial mass, encephalitis, or meningitis, should be considered, with a prevalence of 30-35% 4, 5
Toxicologic/Pharmacologic causes, such as medication side effects, alcohol intoxication, or illicit drug use, should be considered, with a prevalence of 20-25% 1, 6
Metabolic/Systemic causes, such as hypoglycemia, hyperglycemia, electrolyte abnormalities, hepatic encephalopathy, or uremia, should be considered, with a prevalence of 15-20% 1, 3, 7
Infectious causes, such as sepsis, urinary tract infection, pneumonia, or meningitis, should be considered, with a prevalence of 9-18% 3, 5, 7

In patients with cirrhosis, hepatic encephalopathy is a common cause of altered mental status, but remains a diagnosis of exclusion 1
For patients with known intracranial pathology and worsening mental status, neuroimaging should be performed to assess for progression 4, 8
In elderly patients, delirium is often multifactorial and carries higher mortality, and multiple concurrent etiologies should be considered 2

Attributing altered mental status solely to psychiatric causes without adequate medical workup should be avoided 6, 7
Failing to consider multiple concurrent etiologies, especially in elderly patients, should be avoided 2
Relying on ammonia levels alone to diagnose hepatic encephalopathy in cirrhotic patients should be avoided 1
Delaying empiric treatment while awaiting diagnostic results in potentially life-threatening conditions should be avoided 1

History and physical examination have 94% sensitivity for identifying medical conditions, while laboratory studies alone have only 20% sensitivity, and most abnormal laboratory results can be predicted from a careful history and physical examination 10

The yield of acute contributory findings on CT ranges from 2% to 45% based on trial design and inclusion criteria, and 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 11

The American Academy of Pediatrics recommends that altered mental status should not be attributed solely to psychiatric causes without completing a full medical workup, as this is the most dangerous error 12

The American College of Gastroenterology suggests that approximately 90% of patients with suspected hepatic encephalopathy improve with correction of the precipitating factor alone 12
The Infectious Diseases Society of America recommends starting intravenous aciclovir 10 mg/kg three times daily immediately in suspected encephalitis, especially in immunocompromised patients, while awaiting diagnostic results 12

The American College of Radiology suggests that intracranial hemorrhage (subdural, subarachnoid, intraparenchymal) is a significant cause of altered mental status 13
The American College of Radiology recommends considering thyroid disorders (myxedema coma, thyroid storm) as a potential cause of altered mental status 13
The American College of Radiology notes that adrenal insufficiency is a possible cause of altered mental status 13
Urinary tract infection (especially in elderly) is a common infectious cause of altered mental status, according to the American College of Radiology 14
Pneumonia is another infectious cause of altered mental status, as stated by the American College of Radiology 14
The American College of Radiology suggests that primary psychosis (schizophrenia, bipolar disorder, schizoaffective disorder) can be a cause of altered mental status, but should not be attributed without completing full medical workup 13, 14

The American College of Radiology recommends quantifying severity using validated scales (Glasgow Coma Scale, Richmond Agitation Sedation Scale, or West Haven criteria) for patients with altered mental status 13
Delirium may develop in up to 56% of ICU patients, particularly following surgery, according to the American College of Radiology 13
The American College of Radiology states that overall mortality rate is 8.1%, significantly higher in elderly patients 13
The American College of Radiology notes that cause remains undiagnosed in slightly greater than 5% of cases 13