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Updated: Aug 8, 2026
Focal Cerebral Ischemia Model by Endovascular Suture Occlusion of the Middle Cerebral Artery in the Rat
Published on: February 5, 2011
Modest MRI signal intensity changes precede delayed cortical necrosis after transient focal ischemia in the rat
Santiago Rojas1, Abraham Martín, Carles Justicia
1Department of Pharmacology and Toxicology, Institut d'Investigacions Biomèdiques de Barcelona-Consejo Superior de Investigaciones Científicas, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain.
Background And Purpose:
Diffusion-weighted imaging (DWI) hyperintensities and apparent diffusion coefficient (ADC) hypointensities are MRI features of acute stroke. DWI alterations during ischemia recover with early reperfusion, but they can reappear later. Pronounced signal abnormalities early after stroke are associated with infarction, but the significance of subtle changes is unclear. Here we evaluated the degree and time course of regional signal intensity changes during the first 24 hours of reperfusion after transient ischemia, and we related them to the progression of the histopathological damage.
Methods:
Rats (n=54) were subjected to 1-hour intraluminal middle cerebral artery occlusion to assess the dynamics of MRI signal intensity changes during the initial 24 hours and their correspondent histopathological features: 2,3,5-triphenyltetrazolium chloride (TTC) staining, and hematoxylin and eosin, and immunoreactivity to 70-kDa heat shock protein and to astroglial and microglial markers.
Results:
This model of ischemia caused early striatal infarction but delayed necrosis in the cortex. The striatum showed marked MRI changes from 4 hours of reperfusion. By 12 hours, the striatal ADC signal intensity ratio to the homologous contralateral region was 30% reduced, and the TTC staining evidenced infarction. Contrarily, the cortical ADC ratio was only 15% reduced, and TTC staining was normal at 12 hours. After this time, the cortex showed sudden and pronounced (>30%) ADC signal intensity changes coincidentally with the manifestation of infarction, accompanied with severe vacuolation and unambiguous signs of neuronal and astroglial death.
Conclusions:
These findings suggest that minor changes in ADC signal intensity early after ischemia should not be underestimated because they may be harbingers of delayed infarction.
Insights
Subtle MRI changes like reduced apparent diffusion coefficient (ADC) signal intensity after transient ischemia may indicate delayed infarction. Early, minor ADC signal alterations in the cortex can precede significant histopathological damage.
Area of Science:
- Neuroimaging
- Stroke Research
- Histopathology
Background:
- Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) MRI are key for acute stroke detection.
- Early reperfusion can reverse DWI changes, but they may recur.
- The significance of subtle early MRI signal changes in stroke progression remains unclear.
Purpose of the Study:
- To evaluate the temporal dynamics of regional MRI signal intensity changes within 24 hours of reperfusion after transient ischemia.
- To correlate these MRI signal changes with histopathological damage progression.
Main Methods:
- A rat model of transient middle cerebral artery occlusion (1-hour duration) was used (n=54).
- MRI signal intensity changes (ADC) were monitored during the first 24 hours of reperfusion.
- Histopathological analysis included TTC staining and markers for neuronal and glial injury.
Main Results:
- Striatal infarction occurred early, while cortical necrosis was delayed.
- Striatal ADC ratios decreased significantly by 12 hours, correlating with infarction.
- Cortical ADC ratios showed only minor changes early on, but significant decreases (>30%) coincided with infarction onset and cell death.
Conclusions:
- Minor ADC signal intensity reductions early after ischemia should not be dismissed.
- These subtle changes may predict subsequent infarction development, particularly in areas like the cortex.
