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Incidental subcortical lesions identified on magnetic resonance imaging in the elderly. II. Postmortem pathological
Abstract:
The pathological correlates of subcortical lesions noted on magnetic resonance imaging (MRI) in the elderly are not known. Postmortem in vitro proton MRI was performed on the brains of seven consecutive elderly patients dying of nonneurologic causes. Scans were done in the fresh and fixed states with the specimen immersed in saline and formaldehyde respectively. A 1.5 Tesla superconductive system was used with a multiple spin-echo protocol generating T2 weighted images. Subcortical MRI lesions were localized in three dimensions and identified at brain cutting. In addition, pathological correlations were obtained from an eighth patient who underwent MRI eleven days before death. Histological examinations were performed in a blinded fashion, including control areas from the same brains. Subcortical MRI lesions were found to be associated with arteriosclerosis, dilated perivascular spaces, and vascular ectasia (p less than 0.05). These histological changes were characteristic of "état criblé" which, like subcortical MRI lesions, is associated with age and hypertension. Shrinkage (or atrophy) of the brain parenchyma around ectatic blood vessels would result in an extensive network of tunnels filled with extracellular water. The proton MRI signal from such areas of the brain would be increased. Gliosis and small areas of infarction occasionally coexisted with "état criblé," but these were not present in all areas with MRI lesions and could not be distinguished by MRI signal alone. In conclusion, clinical and pathological correlations lend support to the uniform hypothesis that MRI provides a nonspecific index of brain parenchymal alterations caused by aging and chronic cerebrovascular disease.
Insights
Subcortical MRI lesions in elderly brains are linked to arteriosclerosis and dilated perivascular spaces, characteristic of "état criblé." These findings suggest MRI offers a general measure of age-related brain changes and chronic cerebrovascular disease.
Area of Science:
- Neuropathology
- Neuroimaging
- Geriatric Medicine
Background:
- The pathological basis of subcortical lesions observed on magnetic resonance imaging (MRI) in elderly individuals remains unclear.
- Understanding these lesions is crucial for interpreting brain imaging in aging populations.
Purpose of the Study:
- To establish pathological correlates for subcortical MRI lesions in the elderly.
- To investigate the relationship between specific histological findings and MRI signal abnormalities.
Main Methods:
- Postmortem in vitro proton MRI was conducted on seven elderly brains (fresh and fixed states).
- A 1.5 Tesla system with a multiple spin-echo protocol (T2 weighted images) was utilized.
- Histological examination, including blinded analysis, was performed on all specimens, with one patient scanned shortly before death.
Main Results:
- Subcortical MRI lesions correlated significantly with arteriosclerosis, dilated perivascular spaces, and vascular ectasia (p < 0.05).
- These histological changes align with the description of "état criblé," associated with aging and hypertension.
- Increased MRI signal in lesions is attributed to extracellular water in enlarged perivascular spaces (tunnels) due to parenchymal atrophy.
Conclusions:
- MRI findings of subcortical lesions are associated with "état criblé" and chronic cerebrovascular changes.
- MRI serves as a nonspecific indicator of age-related and cerebrovascular-induced brain parenchymal alterations.
- While gliosis and small infarcts can coexist, MRI signal alone cannot differentiate them from "état criblé" changes.