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The morphologic correlate of incidental punctate white matter hyperintensities on MR images
F Fazekas1, R Kleinert, H Offenbacher
1Department of Neurology, Karl-Franzens University, Graz, Austria.
Abstract:
Postmortem examinations were made of the brains of six patients, 52-63 years old, who exhibited incidental punctate white matter hyperintensities on MR images before death. Our aim was to unravel the morphologic correlate of such lesions. By repeating the MR study after fixation on four specimens, cutting the brain parallel to the MR imaging plane, and examining whole-hemisphere microscopic sections, we optimized lesion identification. The white matter signal abnormalities were better delineated on pre- than postmortem scans, and visual inspection of the brain slices was normal in all but one location. Histologically, we found areas of reduced myelination with atrophy of the neuropil around fibrohyalinotic arteries as well as different stages of perivenous damage. The latter ranged from spongiform transformation of the neuropil and scattered foci of demyelination to large perivenous areas with marked rarefaction of myelinated fibers. Edematous glial swelling in foci of ganglion cell heterotopia caused subcortical white matter hyperintensities in one case. Our results suggest minor perivascular damage but not infarction as the most likely substrate of punctate MR white matter hyperintensities in elderly brains. Histologic correlations with MR images obtained during life or with studies of unfixed material are necessary to analyze such small lesions.
Insights
Punctate white matter hyperintensities in elderly brains are likely due to minor perivascular damage, not infarction. Further histologic correlation with in-vivo MR imaging is needed for precise analysis.
Area of Science:
- Neuropathology
- Neuroimaging
- Geriatric Medicine
Background:
- Punctate white matter hyperintensities are common incidental findings on magnetic resonance (MR) images in elderly individuals.
- The precise morphologic substrate of these lesions remains incompletely understood.
Purpose of the Study:
- To investigate the histological correlates of punctate white matter hyperintensities observed on pre-mortem MR imaging.
- To elucidate the underlying pathology responsible for these signal abnormalities in elderly brains.
Main Methods:
- Postmortem examination of six brains from patients aged 52-63 years with pre-mortem MR findings of punctate white matter hyperintensities.
- Repeat MR imaging on fixed specimens, followed by whole-hemisphere sectioning parallel to the MR imaging plane for microscopic examination.
- Histological analysis focused on identifying changes in white matter, including myelination, neuropil, and vascular and perivascular structures.
Main Results:
- White matter signal abnormalities were better delineated on pre-mortem MR scans compared to post-mortem scans.
- Macroscopic visual inspection of brain slices revealed abnormalities in only one location.
- Histological findings included reduced myelination, neuropil atrophy around fibrohyalinotic arteries, and various stages of perivenous damage (spongiform changes, demyelination, fiber rarefaction).
- Subcortical white matter hyperintensities in one case were attributed to edematous glial swelling associated with ganglion cell heterotopia.
Conclusions:
- The most probable cause of punctate white matter hyperintensities in elderly brains is minor perivascular damage, rather than infarction.
- Histological examination suggests that changes related to small vessel disease and perivenous injury are key contributors.
- Further studies correlating in-vivo MR imaging with histological findings are essential for accurate characterization of these small lesions.