MRI Brain Ordering for Persistent Migraines
Direct Answer
For patients with persistent migraines and a normal neurological examination, neuroimaging is not routinely indicated, as the prevalence of significant intracranial abnormalities is only approximately 0.2% 1. However, if imaging is pursued, MRI brain without IV contrast is the preferred modality over CT when structural evaluation is needed 1.
When Neuroimaging Should NOT Be Ordered
- Patients with typical migraine features and completely normal neurological examination do not require routine imaging 1
- The yield of clinically significant findings in this population is equivalent to the general asymptomatic population (approximately 0.2-0.4%) 2, 1
- Patient-directed imaging (when patients insist on scanning despite normal exam) shows no statistical benefit over chance in detecting abnormalities 3
- Testing should be avoided if it will not lead to a change in management 1
Red Flags That MANDATE Neuroimaging
Order MRI brain if any of the following are present 1, 4:
- Abnormal findings on neurological examination (focal deficits, altered mental status, papilledema) 1, 4
- Headache worsened by Valsalva maneuver 1
- Headache that awakens patient from sleep 1
- New-onset headache in older patients (>50 years) 1
- Progressively worsening headache pattern 1
- Rapid increase in headache frequency 1
- Thunderclap headache (sudden severe onset) 1
- Focal neurological symptoms (unilateral weakness, tremor, sensory changes) 4
MRI Protocol Specifications
Standard Protocol (No Red Flags Present)
If imaging is deemed necessary despite normal exam, order: MRI brain without IV contrast 1
This includes:
- T1-weighted sequences 2
- T2-weighted sequences 2
- FLAIR (fluid-attenuated inversion recovery) sequences 2
- Diffusion-weighted imaging (DWI) for stroke evaluation 2
Enhanced Protocol (Red Flags Present)
If abnormal neurological findings are present, order: MRI brain without AND with IV contrast 4
Contrast is essential when:
- Signs suggest possible tumor or mass lesion 4
- Focal neurological deficits are present 4
- Concern for meningeal infiltration exists 4
- Evaluating for enhancing lesions that could cause symptoms 4
MRI vs CT: When to Choose Each
Choose MRI When:
- Elective/outpatient evaluation of persistent headache 1
- Suspected brain tumor or structural lesion 1
- Superior soft tissue resolution needed 1
- Patient can tolerate longer scan time 1
Choose CT When:
- Emergency setting with suspected subarachnoid hemorrhage (CT has 98% sensitivity for acute blood) 1
- Suspected acute intracranial bleeding 1
- MRI is not available or contraindicated 1
- Patient cannot tolerate MRI (claustrophobia, pacemaker, metallic implants) 1
Important caveat: MRI may detect more clinically insignificant abnormalities than CT, but is not necessarily more sensitive for clinically significant pathology 1. CT without contrast is faster and more readily available in acute settings 1.
Common Pitfalls to Avoid
- Do not image "sinus headache" - this is a common misdiagnosis among migraine sufferers, and neuroimaging is not indicated 1
- Do not order MRI without contrast when focal neurological findings are present - this may miss enhancing lesions 4
- Do not use MRI when CT would be more appropriate for detecting acute hemorrhage 1
- Do not perform routine imaging to reassure anxious patients - the yield is no better than the general population 3
- Do not delay appropriate imaging when red flags are present - abnormal neurological findings dramatically increase the likelihood of significant pathology 4
Special Populations
Pediatric Patients:
- MRI without IV contrast is the study of choice for headache evaluation in children 2
- Lower threshold for imaging in children with sickle cell disease due to higher risk of acute CNS events 2
- Occipital headache in children warrants diagnostic caution and consideration of Chiari I malformation evaluation 2