When to Order Imaging for Headache: ACR Appropriateness Decoded
When to Order Imaging for Headache: ACR Appropriateness Decoded
It’s 2 a.m. in the emergency department. A 45-year-old patient presents with the “worst headache of their life,” which reached maximal intensity in under a minute. Your differential includes subarachnoid hemorrhage, and you need to decide on the initial imaging study—fast. Is a non-contrast CT head sufficient, or do you need a CTA? For clinicians on the front lines, choosing the right imaging for headache is a daily challenge, balancing diagnostic yield with radiation exposure and cost. The American College of Radiology (ACR) Appropriateness Criteria provide an evidence-based framework to guide these decisions. This article breaks down the ACR guidelines for headache to help you order the right study for the right patient, every time.
What Does the ACR Guideline for Headache Cover?
The ACR Appropriateness Criteria for Headache focus on selecting the best initial imaging modality for adult and pediatric patients presenting with various headache syndromes. The guidelines are structured around specific clinical variants, from acute, severe “thunderclap” headaches to chronic, stable patterns like migraines. The criteria help differentiate scenarios where imaging is crucial for ruling out life-threatening conditions from those where it is likely low-yield and can be avoided.
This document specifically addresses common clinical questions, such as imaging for suspected intracranial hypertension or hypotension, new-onset headaches in pregnancy, and headaches accompanied by “red flag” symptoms like neurologic deficits or a history of cancer. It does not cover follow-up imaging for known conditions or imaging for headache attributed to trauma where a dedicated head trauma evaluation would be more appropriate.
What Imaging Should I Order for Headache? Recommendations by Clinical Scenario
The optimal imaging strategy for headache is highly dependent on the clinical presentation. The ACR provides clear, scenario-based recommendations to guide ordering physicians.
For a sudden onset severe headache that reaches maximal severity within one hour (a “thunderclap” headache), the primary concern is subarachnoid hemorrhage. In this emergent setting, CT head without IV contrast is rated Usually appropriate as the first-line study due to its high sensitivity for acute blood and rapid availability. For a deeper dive into this protocol, see our guide on CT Brain Without Contrast. If the non-contrast CT is negative but clinical suspicion remains high, CTA head with IV contrast May be appropriate to evaluate for an underlying aneurysm or other vascular pathology.
Conversely, for a patient with a classic presentation of a primary migraine or tension-type headache and a normal neurologic examination, nearly all imaging modalities, including CT and MRI, are rated Usually not appropriate. The diagnostic yield in these cases is extremely low, and the ACR guidance supports a clinical diagnosis without routine neuroimaging.
For primary trigeminal autonomic cephalalgias (eg, cluster headache), MRI head without and with IV contrast is Usually appropriate. This is recommended to exclude secondary causes, such as pituitary or parasellar lesions that can mimic these syndromes. An MRI head without IV contrast May be appropriate as an alternative.
When a headache presents with features of intracranial hypertension (e.g., papilledema, pulsatile tinnitus), several studies are considered Usually appropriate: MRI head without and with IV contrast, MRI head without IV contrast, and CT head without IV contrast. These studies can identify structural causes of elevated pressure, such as a mass or hydrocephalus. MRV or CTV may also be appropriate to evaluate for venous sinus thrombosis as a cause.
In cases of suspected intracranial hypotension (e.g., a positional headache that is worse when upright), MRI head without and with IV contrast is Usually appropriate to look for characteristic findings like pachymeningeal enhancement, sagging of the brainstem, or subdural fluid collections. Spine imaging, such as an MRI of the thoracic spine, May be appropriate to identify the site of a potential CSF leak.
For a headache with new onset or a new pattern during pregnancy or the peripartum period, both MRI head without IV contrast and CT head without IV contrast are Usually appropriate. MRI is often preferred to avoid ionizing radiation, but CT is a rapid and acceptable alternative, particularly if cerebral venous thrombosis or hemorrhage is suspected. Our CT Brain Without Contrast guide provides more detail on dose considerations.
Finally, for a headache accompanied by one or more “red flags” (e.g., new neurologic deficit, history of cancer, onset after age 50, fever), imaging is strongly indicated. MRI head without and with IV contrast, MRI head without IV contrast, and CT head without IV contrast are all rated Usually appropriate to evaluate for underlying structural pathology such as tumor, infection, or stroke.
ACR Imaging Recommendations Table for Headache
| Clinical Scenario | Top Procedure | ACR Rating | Adult RRL | Pediatric RRL |
|---|---|---|---|---|
| Sudden onset severe headache that reaches maximal severity within one hour. Initial imaging. | CT head without IV contrast | Usually appropriate | ☢ ☢ ☢ 1-10 mSv | ☢ ☢ ☢ 0.3-3 mSv [ped] |
| Primary migraine or tension-type headache. Normal neurologic examination. Initial imaging. | (Imaging not indicated) | Usually not appropriate | N/A | N/A |
| Primary trigeminal autonomic cephalalgias (eg, cluster headache). Initial imaging. | MRI head without and with IV contrast | Usually appropriate | O 0 mSv | O 0 mSv [ped] |
| Headache with features of intracranial hypertension. Initial imaging. | MRI head without and with IV contrast | Usually appropriate | O 0 mSv | O 0 mSv [ped] |
| Headache with features of intracranial hypotension. Initial imaging. | MRI head without and with IV contrast | Usually appropriate | O 0 mSv | O 0 mSv [ped] |
| Headache with new onset or pattern during pregnancy or peripartum period. Initial imaging. | MRI head without IV contrast | Usually appropriate | O 0 mSv | O 0 mSv [ped] |
| Headache with one or more “red flags.” Initial imaging. | MRI head without and with IV contrast | Usually appropriate | O 0 mSv | O 0 mSv [ped] |
| Headache without any “red flags.” Initial imaging. | (Imaging not indicated) | Usually not appropriate | N/A | N/A |
Adult vs. Pediatric Headache Imaging: Radiation Dose Tradeoffs
When evaluating headaches in children, the principle of ALARA (As Low As Reasonably Achievable) is paramount due to their increased sensitivity to ionizing radiation and longer life expectancy, which increases the lifetime risk from cumulative exposure. The ACR guidelines reflect this by providing distinct pediatric radiation relative level (RRL) estimates.
For a non-contrast head CT, the adult RRL is ☢ ☢ ☢ (1-10 mSv), while the pediatric RRL is also ☢ ☢ ☢ but corresponds to a lower absolute dose range (0.3-3 mSv) due to size-adjusted protocols. While CT is often necessary in emergent situations like suspected hemorrhage, MRI is frequently the preferred modality for non-emergent “red flag” headaches in children, as it carries an RRL of O (0 mSv). The decision between CT and MRI in a pediatric patient requires careful consideration of the clinical urgency, the need for sedation with MRI, and the long-term risks of radiation. Communicating these tradeoffs with the patient’s family is a key part of the shared decision-making process.
Imaging Protocol Details for Headache
Once you’ve decided on the right study, the specific imaging protocol is critical for diagnostic accuracy. Our protocol library provides detailed, practical guides for the key modalities recommended in the ACR criteria for headache. These resources cover patient preparation, imaging technique, contrast administration, and key interpretation principles.
Tools to Help You Order the Right Study
Navigating imaging guidelines can be complex. GigHz offers a suite of reference tools designed to help clinicians make evidence-based decisions quickly and efficiently at the point of care.
The ACR Appropriateness Criteria Lookup provides direct access to the full ACR guidelines, allowing you to search by clinical topic for scenarios beyond headache. It ensures you are always referencing the most current, evidence-based recommendations for hundreds of clinical presentations.
Our Imaging Protocol Library offers detailed, step-by-step protocols for the imaging studies mentioned in these guidelines. It’s a practical resource for understanding the technical aspects of each exam, from slice thickness on a CT to sequence selection on an MRI.
The Radiation Dose Calculator is a valuable tool for discussing the risks and benefits of imaging with patients. It helps estimate cumulative radiation exposure from various studies, facilitating informed consent and supporting the ALARA principle, especially in younger patients.
Why is imaging not recommended for a typical migraine or tension headache?
For patients with a history of primary headaches like migraine or tension-type headache and a stable pattern with a normal neurologic exam, the diagnostic yield of neuroimaging is exceptionally low. Large-scale studies have shown that the rate of clinically significant findings in this population is similar to that of asymptomatic individuals. Therefore, the ACR designates imaging as “Usually Not Appropriate” to avoid unnecessary radiation exposure, cost, and the potential for incidental findings that can lead to further workup and patient anxiety without changing management.
When is contrast necessary for an MRI of the brain for headache?
Intravenous contrast is recommended for a brain MRI when there is suspicion of a condition that causes breakdown of the blood-brain barrier. This includes concerns for tumor (primary or metastatic), infection (abscess, meningitis), or inflammatory conditions (multiple sclerosis, sarcoidosis). For headache evaluations with “red flags” such as a history of cancer, immunocompromise, or persistent neurologic deficits, a contrast-enhanced MRI is rated “Usually Appropriate” to maximize sensitivity for these pathologies.
What is the difference between MRA and MRV for headache evaluation?
MRA (Magnetic Resonance Angiography) and MRV (Magnetic Resonance Venography) are specialized MRI sequences that visualize blood vessels. MRA is designed to evaluate the arteries and is used to look for aneurysms, stenosis, or dissection. MRV is optimized for the venous system and is the primary study to diagnose cerebral venous sinus thrombosis, a potential cause of headache, particularly in prothrombotic states or the peripartum period.
For a “thunderclap” headache, if the non-contrast head CT is negative, what is the next step?
A negative non-contrast head CT in a patient with a thunderclap headache does not completely rule out a subarachnoid hemorrhage (SAH), as the sensitivity of CT decreases over time from the initial bleed. The classic next step is a lumbar puncture (LP) to look for xanthochromia (yellowish CSF from bilirubin breakdown), which is highly sensitive for SAH. Alternatively, a CTA of the head is often performed to look for a causative aneurysm, even if the non-contrast CT is negative, as it can sometimes identify small aneurysms or other vascular causes of the headache.
Is CT or MRI better for a headache with “red flag” symptoms?
Both CT and MRI are rated “Usually Appropriate” for red flag headaches, but they have different strengths. A non-contrast CT is fast and excellent for detecting acute hemorrhage. However, MRI (preferably with and without contrast) offers superior soft tissue contrast and is much more sensitive for detecting underlying pathologies like tumors, strokes (especially early ischemic or posterior fossa strokes), and signs of infection or inflammation. In a stable patient without contraindications, MRI is generally the preferred study for a comprehensive evaluation of a red flag headache.
Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 12, 2026
