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Deep white matter infarction: correlation of MR imaging and histopathologic findings
V G Marshall1, W G Bradley, C E Marshall
1MR Imaging Laboratory, Hunington Medical Research Institutes, Pasadena, CA 91105.
Abstract:
Focal and confluent areas of periventricular hyperintensity have been reported on magnetic resonance (MR) images in 30% of patients over 60 years of age. In order to better understand the pathologic basis of these lesions, the authors studied 14 formalin-fixed brains with MR imaging. Multiple focal areas of hyperintensity were identified in the periventricular white matter in three of the 14 brains studied (21%). Subsequent gross and microscopic pathologic examination of both hyperintense and normal-intensity areas was performed on 87 tissue sections. The larger lesions were characterized centrally by necrosis, axonal loss, and demyelination and therefore represent true infarcts. Reactive astrocytes oriented along the degenerated axons were identified at distances of up to several centimeters from the central infarct. This is called isomorphic gliosis and is associated with increased intensity on T2-weighted images that increases the apparent size of the central lesion.
Insights
Periventricular white matter hyperintensities seen on MRI in older adults are often true infarcts. These lesions, characterized by necrosis and demyelination, can appear larger due to associated isomorphic gliosis.
Area of Science:
- Neuropathology
- Neuroimaging
- Geriatric Medicine
Background:
- Periventricular white matter hyperintensities are common findings on magnetic resonance (MR) images in individuals over 60.
- These lesions are observed in approximately 30% of this age group.
Purpose of the Study:
- To investigate the pathological basis of periventricular white matter hyperintensities observed on MR imaging.
- To correlate imaging findings with gross and microscopic pathological examination.
Main Methods:
- MR imaging was performed on 14 formalin-fixed human brains.
- Gross and microscopic pathological examination of 87 tissue sections from both hyperintense and normal-appearing areas were conducted.
Main Results:
- Multiple focal areas of periventricular white matter hyperintensity were identified in 21% of the studied brains.
- Larger lesions exhibited central necrosis, axonal loss, and demyelination, consistent with infarcts.
- Isomorphic gliosis, characterized by reactive astrocytes, was found extending from infarcts and contributed to increased T2-weighted signal intensity.
Conclusions:
- Periventricular white matter hyperintensities on MR imaging in older adults often represent true infarcts.
- The apparent size of these infarcts is increased by associated isomorphic gliosis, a reactive astrogliosis process.