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Cerebral microembolization. II. Morphological studies
Insights
Massive microembolization in cats caused brain death within four hours. This study reveals how emboli distribution and blood-brain barrier damage lead to brain edema and neurodegeneration.
Area of Science:
- Neuroscience
- Cerebrovascular Research
- Pathology
Background:
- Microembolization is a significant factor in cerebrovascular events.
- Understanding the immediate effects of microemboli on brain tissue is crucial for developing therapeutic strategies.
Purpose of the Study:
- To investigate the acute effects of massive cerebral microembolization on brain structure and function in a feline model.
- To characterize the distribution of microspheres and the subsequent blood-brain barrier integrity changes.
Main Methods:
- Cats received carotid infusion of microspheres, inducing massive microembolization.
- Intravascular dyes (Evans blue, sodium fluorescein) were used to assess blood-brain barrier permeability.
- Fluorescence microscopy examined emboli distribution, hyperemia, extravasation, and tissue damage.
Main Results:
- Microembolization led to brain death within 4 hours, with most emboli impacting the ipsilateral hemisphere's grey matter.
- Initial hyperemia was observed, followed by multifocal blood-brain barrier extravasations in the cortex and basal ganglia.
- Severe vasogenic brain edema developed, migrating into white matter and causing neuroglial and axonal swelling, leading to secondary white matter damage and cortical degenerative foci.
Conclusions:
- Massive microembolization causes rapid brain death and significant blood-brain barrier disruption.
- Edema migration from grey to white matter contributes to secondary white matter injury following embolic stroke.
- Early hyperemia and blood-brain barrier damage correlate with subsequent degenerative changes in the cerebral cortex.
Abstract:
Cats underwent massive microembolization via carotid infusion of 10.5 million microspheres (15 +/- 5 mu in diameter), resulting in brain death within four hours; 87.4 +/- 10.2% of emboli reaching the brain were in the ipsilateral hemisphere; 87.9 +/- 4.4% were in the grey matter; and 12.1 +/- 4.4% were in the white matter. Evans blue and sodium fluorescein dyes were given intravascularly before and at different times after embolization. Fluorescence microscopy disclosed that embolization initially provoked a hyperemic engorgement of both the embolized and nonembolized hemispheres. Multifocal, blood-brain barrier extravasations occurred throughout the ipsilateral cortex and oral basal ganglia. Severe vasogenic brain edema ensued, with migration of extravasations from cortex into the white matter, which initially showed only minimal injury. Migration and accumulation of edema in white matter, with subsequent uptake and swelling of neuroglia and axons, may be related to secondary white matter damage following cortical embolic lesions. Degenerative foci developed throughout the embolized cortex over the one- to four-hour period of this study. These sites may correspond to those areas in which hyperemia and damage to the blood-brain barrier was present shortly after embolization.