Characteristic Progression of Neurodegeneration in Alzheimer's Disease

Biomarker Model of Neurodegeneration in AD

Brain atrophy on structural MRI in AD follows a characteristic pattern involving the medial temporal lobes, paralimbic and temporoparietal cortices, representing a biomarker of AD-related neurodegeneration 1
Structural MRI changes typically become abnormal later in the disease progression compared to amyloid biomarkers, serving as a marker of neuronal loss that correlates closely with cognitive performance through MCI and dementia phases 1, 2
The pattern of neurodegeneration follows a predictable sequence in the biomarker model of AD, with amyloid accumulation occurring first, followed by synaptic dysfunction, and then structural changes visible on MRI 1

Medial temporal atrophy affecting the amygdala and hippocampus, usually accompanied by enlargement of the temporal horn, is typical of AD 3
Other characteristic features include moderate cortical atrophy, most evident in multimodal association between cortices and limbic lobe structures 3
Enlarged sulcal spaces with atrophy of the gyri in frontal and temporal cortices are also commonly observed in AD 3

The severity and progression of structural changes on MRI correlate with cognitive performance through the clinical phases of MCI and dementia 1
Neurodegeneration biomarkers, including structural MRI, are considered stage markers that progress in close concordance with clinical symptoms 4
Anatomic information from imaging biomarkers provides useful disease staging information as the topography of disease-related imaging abnormalities changes in a characteristic manner with disease progression 1

Brain or cognitive reserve may influence the relationship between structural changes and clinical symptoms 2
The concept of reserve explains why the extent of AD histopathological changes doesn't always align with the degree of clinical impairment 2
Higher education and socioeconomic status have been associated with lower age-adjusted incidence of AD diagnosis, suggesting these factors may contribute to reserve capacity 2

Structural MRI without contrast is appropriate for evaluation of AD when available and not contraindicated, according to the Alzheimer's and Dementia guidelines 5
Atrophy patterns seen on brain MRI predict neuropathological findings with a high level of accuracy, although not as high as molecular biomarkers 5
When a clinician's hypothesis is that cognitive impairment is likely due to AD and brain MRI shows supportive atrophy patterns, this increases confidence in the clinical diagnosis 5

Structural changes alone are not specific for AD and must be interpreted in the context of clinical presentation and other biomarkers 5
AD is rarely found in isolation, and vascular pathology is the most common concurrent pathology in patients with AD 3
Atrophy patterns may overlap with other neurodegenerative conditions, requiring careful differential diagnosis 3