MRI Brain Without Contrast for Dementia Workup
For initial dementia evaluation in older adults with progressive cognitive decline and no focal neurologic deficits, perform brain MRI without gadolinium contrast. 1, 2
Primary Recommendation
The American College of Radiology designates MRI brain without IV contrast as "usually appropriate" for initial imaging across all dementia subtypes, including Alzheimer disease, frontotemporal dementia, dementia with Lewy bodies, vascular dementia, and idiopathic normal-pressure hydrocephalus. 1 Contrast administration is not needed for standard dementia workup because the diagnostic findings are optimally visualized on noncontrast sequences. 1
Why Contrast Is Not Necessary
All critical imaging findings for dementia diagnosis—including atrophy patterns, ventricular enlargement, white matter changes, and microhemorrhages—are best detected on noncontrast MRI sequences. 1, 2
The goal of imaging is to exclude treatable structural causes (tumors, subdural hematomas, normal-pressure hydrocephalus) and identify atrophy patterns that suggest specific neurodegenerative diagnoses, neither of which requires contrast. 2, 3
Research demonstrates that white matter lesions in dementia patients show no significant signal changes after gadolinium administration, indicating that contrast does not add diagnostic value for typical dementia evaluation. 4
Essential MRI Protocol Components (All Without Contrast)
3D T1 volumetric sequence with coronal reformations to assess hippocampal volume and medial temporal lobe atrophy 5
FLAIR imaging to evaluate white matter hyperintensities using the Fazekas scale 2, 5
T2-weighted or susceptibility-weighted imaging (SWI) to detect microhemorrhages, which are critical for identifying patients at risk for amyloid-related imaging abnormalities (ARIA) if antiamyloid therapy is considered 2, 5
Diffusion-weighted imaging (DWI) to identify acute pathology such as infarction 5
When Contrast May Be Appropriate (Exceptions to the Rule)
Contrast-enhanced MRI should be reserved for rapidly progressive dementia (RPD) to evaluate for infectious, inflammatory, or neoplastic causes that can mimic neurodegenerative dementia. 3 This includes:
Suspected CNS lymphoma (lymphomatosis cerebri), which can present as rapidly progressive dementia with diffuse leukoencephalopathy 6
History of cancer with risk for brain metastases 5
Unexplained neurological manifestations such as new severe headache or seizures 5
Recent significant head trauma 5
CT as an Alternative
CT head without contrast is considered an equivalent alternative by the American College of Radiology when MRI is unavailable or contraindicated, though MRI is strongly preferred due to superior sensitivity for detecting vascular lesions, hippocampal atrophy, and microhemorrhages. 1, 2
If CT is used, request coronal reformations to better visualize hippocampal atrophy. 5
Common Pitfalls to Avoid
Do not routinely order contrast "just in case"—this exposes patients to unnecessary gadolinium, increases cost, and does not improve diagnostic accuracy for typical dementia presentations. 1, 2
Do not use advanced MRI techniques (MR spectroscopy, functional MRI, diffusion tensor imaging) for routine clinical dementia evaluation, as these are not recommended outside research settings. 5, 3
Remember that most patients over age 80 with cognitive impairment have mixed pathology, so imaging findings should be interpreted in conjunction with clinical presentation and biomarkers. 2