When to Order Imaging for Altered Mental Status, Coma, Delirium, and Psychosis: ACR Appropriateness Decoded

When to Order Imaging for Altered Mental Status, Coma, Delirium, and Psychosis: ACR Appropriateness Decoded

It’s 2 AM in the emergency department, and you’re evaluating an 84-year-old patient with an acute change in mental status. The differential is broad, ranging from urosepsis to an intracranial hemorrhage. You need to decide on the right initial imaging study, balancing diagnostic yield with speed and radiation exposure. A non-contrast head CT is fast and readily available, but is it the most appropriate first step? This common clinical challenge is where the American College of Radiology (ACR) Appropriateness Criteria provide essential, evidence-based guidance. This article decodes the ACR recommendations for imaging in patients with altered mental status, coma, delirium, and psychosis to help you make the right call, every time.

What Does ACR Altered Mental Status, Coma, Delirium, and Psychosis Cover?

The ACR Appropriateness Criteria for “Altered Mental Status, Coma, Delirium, and Psychosis” focus on the initial imaging workup for adult patients presenting with an acute, non-traumatic change in their level of consciousness, awareness, or cognitive function. This includes a wide spectrum of presentations, from mild confusion and delirium to unresponsiveness (coma) and new-onset psychosis. The guidelines are designed to help clinicians identify potential underlying intracranial pathologies such as stroke, hemorrhage, mass, or infection that may be causing the patient’s symptoms.

These criteria specifically address initial imaging decisions. They do not cover the evaluation of patients with head trauma, known or suspected seizures, chronic cognitive decline (dementia), or the follow-up imaging of established conditions. For those clinical scenarios, the ACR provides separate, dedicated guidelines. The focus here is on the undifferentiated patient where an acute central nervous system cause must be considered and appropriately investigated.

What Imaging Should I Order for Altered Mental Status, Coma, Delirium, and Psychosis? Recommendations by Clinical Scenario

The optimal imaging strategy depends heavily on the clinical context, including the presence of focal neurologic deficits and the suspected underlying etiology. The ACR provides guidance across several common clinical variants.

For an adult with altered mental status and suspected intracranial pathology or a focal neurologic deficit, the initial imaging choice is clear. The ACR rates CT head without IV contrast as Usually appropriate. This modality is fast, widely accessible, and highly sensitive for detecting acute intracranial hemorrhage, which is a critical diagnosis to make or exclude immediately. While MRI of the head without contrast and MRI without and with IV contrast are rated May be appropriate, they are typically reserved for situations where the initial CT is non-diagnostic but clinical suspicion for pathology like an ischemic stroke, encephalitis, or a mass remains high.

In a patient with altered mental status who has a known history of intracranial pathology (e.g., a brain tumor), the imaging recommendations shift. Here, MRI head without and with IV contrast and MRI head without IV contrast are both rated Usually appropriate. MRI provides superior soft-tissue detail to evaluate for progression of the known disease. A CT head without IV contrast is also Usually appropriate, often serving as a rapid first-look examination to rule out acute complications like hemorrhage before a more detailed MRI is performed.

When altered mental status is suspected to be from a medical illness or a toxic-metabolic cause (e.g., sepsis, hypoglycemia, uremia), the role of imaging is less certain. For this scenario, both MRI head without IV contrast and CT head without IV contrast are rated May be appropriate (Disagreement). The “Disagreement” qualifier indicates that the expert panel did not reach a consensus, reflecting that imaging may not be necessary if the clinical picture strongly points to a systemic cause and the patient is improving with treatment. However, if the patient’s mental status fails to improve despite clinical management of the known medical illness, the suspicion for a primary intracranial process increases. In this case, a CT head without IV contrast becomes Usually appropriate to exclude an occult structural cause.

For an adult presenting with new onset psychosis, imaging is used to rule out an underlying organic cause. The ACR rates MRI head without and with IV contrast, MRI head without IV contrast, and CT head without IV contrast as May be appropriate. MRI is often favored in this setting due to its higher sensitivity for detecting subtle inflammatory, demyelinating, or neoplastic processes that can manifest with psychiatric symptoms.

ACR Imaging Recommendations Table

Adult vs. Pediatric Altered Mental Status, Coma, Delirium, and Psychosis Imaging: Radiation Dose Tradeoffs

While this ACR document focuses on adult presentations, the principles of radiation safety are paramount when considering imaging for any patient, especially children. The concept of As Low As Reasonably Achievable (ALARA) is a cornerstone of medical imaging. Children are more radiosensitive than adults, and their longer life expectancy provides more time for potential long-term effects of radiation exposure to manifest. For this reason, there is a lower threshold to consider non-ionizing modalities like MRI in pediatric patients when clinically appropriate.

As shown in the table, the relative radiation level (RRL) for a head CT is lower for pediatric protocols (0.3-3 mSv) than for adult protocols (1-10 mSv), reflecting dose-reduction techniques used for younger patients. However, even with these adjustments, the decision to perform a CT scan in a child requires careful consideration of the risk-benefit ratio. When MRI is a viable alternative and its longer acquisition time or need for sedation is not a barrier to care, it is often the preferred modality to avoid ionizing radiation entirely.

Imaging Protocol Details for Altered Mental Status, Coma, Delirium, and Psychosis

Once you’ve decided on the right study based on the clinical scenario, the specific imaging protocol is critical for maximizing diagnostic value. Our protocol guides provide detailed, practical information on technique, contrast administration, and key interpretation principles for the studies recommended in these ACR criteria.

• CT Brain Without Contrast

Tools to Help You Order the Right Study

Navigating imaging guidelines and radiation safety can be complex. GigHz provides a suite of reference tools designed to support clinicians in making evidence-based decisions at the point of care.

The ACR Appropriateness Criteria Lookup tool provides direct access to the full library of ACR guidelines, allowing you to quickly find recommendations for hundreds of clinical scenarios beyond altered mental status.

For detailed procedural information, the Imaging Protocol Library offers in-depth guides on how specific studies are performed, helping you understand the nuances of different imaging techniques.

To facilitate discussions about radiation exposure with patients and their families, the Radiation Dose Calculator helps estimate cumulative radiation dose from various imaging studies, supporting informed consent and adherence to ALARA principles.

FAQ

Why is non-contrast CT head the first choice so often for altered mental status?

A non-contrast head CT is frequently the first-line imaging study due to its speed, wide availability, and excellent sensitivity for detecting acute intracranial hemorrhage. In an undifferentiated patient with altered mental status, ruling out a life-threatening bleed is a top priority, and CT accomplishes this in minutes.

When should I order an MRI instead of a CT for initial workup of altered mental status?

An MRI should be considered when there is a high clinical suspicion for a condition that is poorly visualized on CT. This includes acute non-hemorrhagic stroke (especially in the posterior fossa), encephalitis, cerebral venous thrombosis, demyelinating disease, or a small tumor. It is also the preferred modality if the initial CT is negative but the patient’s symptoms persist or worsen.

Is imaging always necessary for delirium from a known cause like a UTI?

Not always. According to the ACR, for patients with altered mental status from a suspected medical or toxic-metabolic cause, imaging is rated as “May be appropriate (Disagreement).” This indicates that if a clear systemic cause is identified (like a urinary tract infection) and the patient’s mental status improves with treatment of that cause, imaging may be safely deferred. Imaging becomes more appropriate if the patient fails to improve as expected.

Why is IV contrast not always recommended for initial head imaging in altered mental status?

Many of the most urgent diagnoses, such as acute hemorrhage and large territory ischemic stroke, are readily identified on non-contrast studies. Administering IV contrast adds time to the examination, carries a small risk of allergic reaction or contrast-induced nephropathy, and increases cost. Contrast is most valuable when there is a specific concern for a process that enhances, such as a tumor, abscess, or certain types of inflammation, and is often reserved for a second step after a non-contrast study has been performed.

What does the ACR rating ‘May be appropriate (Disagreement)’ mean?

This specific rating signifies that the expert panel that developed the guidelines did not reach a consensus on the appropriateness of the procedure for that clinical scenario. It highlights an area where the evidence may be less definitive or where patient-specific factors and clinical judgment play a particularly large role in the decision-making process. Some experts on the panel found the procedure appropriate, while others did not.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 12, 2026