Cognitive impairment or suspected dementia
ACR AC Dementia (2024 update)Imaging here does two jobs: exclude the small number of structural causes that are treatable, and characterise the pattern of atrophy and vascular burden that supports a specific diagnosis. Neither needs gadolinium.
Progressive cognitive decline referred from a memory service or from primary care, usually over months, with the differential spanning neurodegenerative, vascular and structural causes.
Referenced decision support — confirm against your local protocol.
Decision support, not a directive. Protocols and timings shown are typical published ones — your local protocol takes precedence, and the vetting radiologist decides.
Accept as requested
MRI Brain — routine unenhanced
MRI Brain
What we'd amend, and why
- Two distinct yields justify the study. The first is exclusion of a structural cause that would change everything — chronic subdural collection, tumour, hydrocephalus — which is uncommon but not negligible. The second is positive characterisation: coronal sections through the hippocampi allow medial temporal atrophy to be graded, susceptibility imaging shows the lobar microbleeds of amyloid angiopathy, and FLAIR quantifies the small vessel burden that supports a vascular contribution. All of that is achieved without contrast.
Nothing needs resolving before this goes ahead. Routine checks below are owned downstream.
How was this decided?
- pathwayadult — Adults
- rulerule-mr-device-screening — MR safety screening for implants and foreign bodies; checked by Radiographer at the scanner
- rulerule-paeds-sedation — Sedation or anaesthesia for a child; checked by Nurse before the scan
Decision support only. Local protocol takes precedence.
Handled at the scanner(1)nothing for you to do
Settled and owned downstream. Each returns to a radiologist only on the stated trigger.
- MR safety screening for implants and foreign bodiesComplete the MR safety questionnaire, verify implant labelling and its stated conditions of use against this scanner and this protocol, and ensure no ferromagnetic object enters Zone IV.Radiographer at the scannerBefore the scanFlags back if: An implant or retained foreign body that is MR Unsafe, unlabelled, or cannot be identified; or an MR Conditional device whose stated conditions this scanner or the requested protocol cannot satisfy; or a credible unexcluded intraocular metallic foreign body history.
Pathways
Big forks are separate pathways; the first whose conditions match is the one used.
Adults
Matches your inputsDefault| Role | Study & protocol | Why this answers the question |
|---|---|---|
| First line | MRI Brain MRI Brain — routine unenhanced usually appropriate | Two distinct yields justify the study. The first is exclusion of a structural cause that would change everything — chronic subdural collection, tumour, hydrocephalus — which is uncommon but not negligible. The second is positive characterisation: coronal sections through the hippocampi allow medial temporal atrophy to be graded, susceptibility imaging shows the lobar microbleeds of amyloid angiopathy, and FLAIR quantifies the small vessel burden that supports a vascular contribution. All of that is achieved without contrast. |
| Reasonable alternative | CT Head CT Head — Unenhanced | Adequate for the exclusion job and widely used where MRI is not tolerated or not available. It performs the structural screen and gives a crude atrophy assessment, but it cannot grade medial temporal atrophy reliably, cannot show microbleeds at all, and substantially underestimates small vessel disease. |
| Problem solving | FDG PET-CT FDG PET-CT — skull base to mid-thigh | Reserved for cases where structural imaging is non-discriminating and the distinction between syndromes — particularly Alzheimer disease against frontotemporal dementia — would change management. It reports a metabolic pattern rather than a structural one and is interpreted alongside the MRI. |
Pitfalls
- Adding gadolinium routinely, which contributes nothing to this question and adds cost and exposure.
- Reporting "age-related atrophy" without grading the pattern, which discards most of the diagnostic value of the study.
- Missing a chronic subdural collection, which is isodense to brain at a particular age and is the classic treatable miss.
- Failing to escalate a rapidly progressive presentation, where cortical ribboning on diffusion or limbic signal change points to prion disease or autoimmune encephalitis.
- Attributing decline to small vessel disease without considering that mixed pathology is the rule rather than the exception.
Priors — what to pull first
- Serial studies convert a subjective impression of atrophy into a rate, which is far more informative than any single scan.
- Check whether a previous study already excluded structural causes; the second scan in a stable patient rarely adds anything.
What makes a good request
- State the cognitive domains affected and the tempo. Rapidly progressive decline over weeks is a different and more urgent differential — prion disease, autoimmune encephalitis, malignancy — and needs diffusion and contrast.
- Report the pattern, not just the presence of atrophy: medial temporal, parietal, frontotemporal or posterior cortical distributions each point somewhere different, and visual rating scales make that reproducible.
- Contrast has no routine role in this question and should be reserved for a suspected neoplastic, inflammatory or infective cause.
Scoring this once it is done
The classification and risk tools this question ends in.
How these studies are acquired
Contrast, phases and timing for every study on the pathways above.
Confirm locally
- MRI Brain — routine unenhanced: timings are typical — confirm against local protocol.
- Timings, contrast volumes and rates above are typical published values. Your department's protocol, scanner and patient population decide the actual numbers.
- Safety thresholds and premedication policy follow local policy where it differs from the cited guidance.
References
- ACR Appropriateness Criteria — Dementia (2024 update) · ACR Appropriateness Criteria
- American College of Radiology Manual on MR Safety: 2024 Update and Revisions. Radiology. · ACR MR Safety
- ACR Manual on MR Safety — zoning, MR Safe / MR Conditional / MR Unsafe labelling, and screening of patients and personnel · ACR MR Safety
- Safety of MRI in patients with cardiac implantable electronic devices — conditions of use, device interrogation and monitoring · Primary literature
- AAP/AAPD Guidelines for Monitoring and Management of Pediatric Patients Before, During, and After Sedation for Diagnostic and Therapeutic Procedures. Pediatrics 2019;143(6):e20191000. · Other
- Sedation and anaesthesia for imaging of the infant and neonate — a brief review (feed-and-wrap, fasting, monitoring) · Primary literature
- Image Gently — reducing the need for sedation through preparation and faster protocols in paediatric imaging · Image Gently
Implemented from the cited published sources. Educational and workflow support only; confirm against current guidelines and local policy before clinical use.