MRI Findings Indicative of Alzheimer's Disease

Primary Structural Findings on Standard MRI

The American College of Radiology recommends that medial temporal lobe atrophy, specifically hippocampal atrophy, is the most diagnostically valuable MRI finding for Alzheimer's disease, which can predict conversion to AD with 80% accuracy 1
Entorhinal cortex volume loss occurs earliest in the disease process, preceding hippocampal changes, according to the American College of Radiology 2, 3
Lateral temporal and parietal lobe atrophy with ventricular enlargement represents more advanced disease, as stated by the American College of Radiology, although this finding is also reported by Praxis Medical Insights 4, 5

Hippocampal volume measurements provide the best discrimination between AD patients and controls, with sensitivity of 83% and specificity of 80-89%, as recommended by the American College of Radiology 1
Supramarginal gyrus thickness and entorhinal cortex thickness measurements aid risk stratification, according to the American College of Radiology 1, 6

Elevated apparent diffusion coefficient (ADC) values in the hippocampi, cingulate, parahippocampal gyri, and temporal/frontal lobes distinguish AD from healthy controls, as reported by the American College of Radiology 1, 6, 3
Diffusion tensor imaging demonstrates reduced fractional anisotropy in the precuneus, according to the American College of Radiology 3
Decreased N-acetylaspartate (NAA) to creatine (Cr) ratios correlate with cognitive decline, as stated by the American College of Radiology 1, 6
Elevated myoinositol (myI) to Cr ratios and elevated choline (Cho) to Cr ratios predict AD development, according to the American College of Radiology 1, 6
Decreased NAA to myoinositol ratios distinguish AD from mild cognitive impairment, as reported by the American College of Radiology 7
Arterial spin labeling shows hypoperfusion patterns similar to FDG-PET findings in temporoparietal regions, according to the American College of Radiology 3

Early-onset AD patients are less likely to manifest typical atrophy patterns, making them better candidates for amyloid PET imaging, as stated by the American College of Radiology 2, 3

The American College of Radiology recommends that MRI brain without IV contrast is the appropriate initial imaging study for suspected AD 1, 8, 4
Contrast is not needed for dementia evaluation unless excluding other pathology, according to the American College of Radiology 2, 3
MRI is mandatory before initiating antiamyloid therapy to identify pre-existing microhemorrhages and monitor for amyloid-related imaging abnormalities (ARIA), as stated by the American College of Radiology 4

The American College of Radiology recommends brain amyloid PET/CT for pretreatment imaging before initiating antiamyloid monoclonal antibody therapy, demonstrating the presence of amyloid in brain parenchyma 9
Brain amyloid PET/CT results in a change in diagnosis of suspected etiology of cognitive impairment in 25% to 44% of patients, increasing diagnostic confidence 10
Amyloid PET/CT is positive in up to 60% of patients with mild cognitive impairment, with correlation between amyloid burden and cognitive test performance 10
The American College of Radiology recommends brain FDG-PET/CT to demonstrate characteristic hypometabolism patterns in temporal and parietal cortex 9
Patients with mild cognitive impairment who progress to dementia have lower FDG uptake in temporal and parietal cortex, whereas a negative FDG-PET/CT indicates progression from mild cognitive impairment to dementia is unlikely 10
Amyloid PET/CT and FDG-PET/CT are complementary and when combined have better accuracy at predicting conversion of patients with mild cognitive impairment to Alzheimer's disease 10
CT can detect large intracranial masses, subdural hematomas, or other structural abnormalities that may produce clinical symptoms mimicking Alzheimer's disease 10

The American College of Radiology recommends MRI brain without IV contrast as the appropriate initial imaging study for all dementia evaluations 9
MRI brain without IV contrast is the only recommended imaging study for post-treatment monitoring to detect amyloid-related imaging abnormalities (ARIA) 9
Brain amyloid PET/CT can demonstrate clearance of amyloid from brain parenchyma after treatment 9
The American College of Radiology recommends against using MR spectroscopy, fMRI, brain perfusion SPECT/CT, and brain striatal SPECT/CT as initial imaging tests for Alzheimer's disease evaluation 9, 10