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MR detection of cortical spreading depression immediately after focal ischemia in the rat
J Röther1, A J de Crespigny, H D'Arceuil
1Department of Radiology, Stanford University, California 94305-5489, USA.
Abstract:
The suture model for middle cerebral artery occlusion (MCAO) was used to induce acute ischemia in rats remotely within a magnetic resonance (MRI) scanner. Serial MR diffusion weighted imaging (DWI) was performed during remote MCAO using an echo planar imaging technique. MR perfusion imaging was performed before and after occlusion using the bolus tracking technique. Transient apparent diffusion coefficient (ADC) changes were detected in six of seven rats as early as 2.7 +/- 1.5 min post MCAO. ADC values declined transiently to 70.1 +/- 6.0% of control and recovered to 95.5 +/- 6.8% of control within 3.3 +/- 2.9 min. These ADC changes propagated bidirectionally away from the ischemic core with a speed of 3.0 +/- 1.1 mm/min. Transient ADC decreases only occurred in ischemic areas characterized by moderately decreased tissue perfusion. Propagation toward cortical regions with severe tissue perfusion deficits was not detected. DWI can detect the earliest dynamic, reversible ADC changes in the ischemic tissue. The speed of propagation of the decreasing ADC wave, the waveform characteristics, and the occurrence in moderately perturbated tissue are compatible with cortical spreading depression.
Insights
Diffusion-weighted imaging detected early, reversible changes in apparent diffusion coefficient during rat middle cerebral artery occlusion. These dynamic changes suggest a link between ischemia, perfusion, and cortical spreading depression.
Area of Science:
- Neuroscience
- Radiology
- Ischemic Stroke Research
Background:
- Acute ischemic stroke poses significant challenges in early detection and understanding of underlying pathophysiological mechanisms.
- Magnetic Resonance Imaging (MRI) offers advanced techniques for monitoring brain tissue during ischemic events.
Purpose of the Study:
- To investigate the earliest dynamic changes in apparent diffusion coefficient (ADC) during acute ischemic stroke using MRI.
- To characterize the propagation patterns and physiological correlates of these early ADC changes in a rat model.
Main Methods:
- Induction of acute ischemia via middle cerebral artery occlusion (MCAO) in rats within an MRI scanner.
- Serial diffusion-weighted imaging (DWI) and perfusion imaging using echo planar and bolus tracking techniques.
- Analysis of transient ADC changes and their spatiotemporal propagation patterns relative to tissue perfusion.
Main Results:
- Transient ADC decreases were detected as early as 2.7 minutes post-MCAO in 6 of 7 rats.
- ADC values dropped to 70.1% of control and recovered within 3.3 minutes, propagating at 3.0 mm/min.
- These reversible ADC changes occurred in areas of moderate hypoperfusion and were not detected in severely affected regions.
Conclusions:
- Diffusion-weighted imaging can detect early, dynamic, and reversible ADC alterations in ischemic brain tissue.
- The observed ADC changes and their propagation characteristics are consistent with cortical spreading depression during acute ischemia.
- Findings highlight the potential of DWI in characterizing early ischemic events and their relationship to perfusion deficits.