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Sequential changes in ischemic edema following transient focal cerebral ischemia in rats: magnetic resonance imaging
1Department of Neurosurgery, Kumamoto University Medical School.
Abstract:
Sequential and regional changes in ischemic edema following various durations of focal cerebral ischemia were studied by magnetic resonance (MR) imaging in a rat unilateral intraluminal middle cerebral artery occlusion model. Occlusion was performed from 5 minutes to 5 hours. T2-weighted images were obtained chronologically 6 hours after onset of ischemia, on day 1 and day 7. An immunohistochemical study using antibodies to calcineurin and glial fibrillary acidic protein was performed to observe histological changes in the ischemic brain. The T2 high-signal-intensity areas representing ischemic edema were observed in the lateral striatum and/or the cerebral cortex by day 1 in all rats with 1- to 5-hour ischemia, and the areas were larger and detected earlier with longer durations of ischemia. In three of six rats with 15-minute ischemia and five of six rats with 30-minute ischemia, the T2 high-signal-intensity areas appeared transiently on day 1 in the dorsolateral striatum where loss of neurons expressing calcineurin immunoreactivity and associated gliosis were found. MR imaging in animal models of reversible focal ischemia can achieve sequential and noninvasive evaluation of dynamic regional changes in ischemic edema.
Insights
Magnetic resonance imaging reveals that ischemic edema in rats develops faster and is larger with longer durations of focal cerebral ischemia. This noninvasive technique allows for dynamic evaluation of edema changes in reversible ischemia models.
Area of Science:
- Neuroscience
- Medical Imaging
- Pathology
Background:
- Focal cerebral ischemia leads to ischemic edema, a critical factor in brain injury.
- Understanding the temporal and regional dynamics of edema is crucial for developing effective treatments.
- Magnetic resonance (MR) imaging offers a noninvasive method to study these changes.
Purpose of the Study:
- To investigate the sequential and regional changes in ischemic edema following varying durations of focal cerebral ischemia.
- To correlate MR imaging findings with histological changes in the ischemic brain.
- To assess the utility of MR imaging in evaluating dynamic edema changes in reversible ischemia models.
Main Methods:
- A rat model of unilateral intraluminal middle cerebral artery occlusion was used, with occlusion durations ranging from 5 minutes to 5 hours.
- T2-weighted MR images were acquired at 6 hours, 1 day, and 7 days post-ischemia.
- Immunohistochemistry was performed to assess calcineurin and glial fibrillary acidic protein expression, indicative of neuronal loss and gliosis.
Main Results:
- Ischemic edema, visualized as T2 high-signal-intensity areas, was detected by day 1 in rats with 1- to 5-hour ischemia, primarily in the lateral striatum and cerebral cortex.
- Edema areas were larger and appeared earlier with longer occlusion durations.
- Transient edema on day 1 in the dorsolateral striatum correlated with calcineurin-negative neurons and gliosis in shorter ischemia durations (15-30 minutes).
Conclusions:
- MR imaging can effectively monitor sequential and regional changes in ischemic edema in animal models.
- The extent and timing of edema correlate with the duration of focal cerebral ischemia.
- MR imaging provides a valuable noninvasive tool for evaluating dynamic edema changes in reversible focal ischemia.