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Rapid alterations in diffusion-weighted images with anatomic correlates in a rodent model of status epilepticus
C J Wall1, E J Kendall, A Obenaus
1Academic Department of Medical Imaging, Royal University Hospital, University of Saskatchewan, Saskatoon, Canada.
Background And Purpose:
Diffusion-weighted MR imaging has emerged as a noninvasive tool for the detection of regional neuronal damage. We hypothesize that changes in diffusion-weighted images will correlate with pathophysiologic alterations caused by pilocarpine-induced status epilepticus.
Methods:
MR images of brain tissues were examined in vivo by use of T2- and diffusion-weighted imaging at 3, 6, 12, and 24 hours after pilocarpine-induced seizures. Histologic verification of neuronal damage was also performed after imaging to assess the extent and the time course of neuronal cell death.
Results:
The piriform cortex, amygdala, and retrosplenial (and somatosensory) cortex displayed significant apparent diffusion coefficient (ADC) decreases 12 hours after seizure initiation. In contrast, an ADC rise of 19% was observed in the hippocampus 24 hours after seizure induction. Histologic data from the piriform cortex and amygdala confirmed severe neuronal loss, whereas hippocampal damage was much less pronounced at 12 hours. Interestingly, very little histologic damage was seen in the retrosplenial cortex.
Conclusion:
This study capitalized on diffusion-weighted imaging as a sensitive technique for the early identification of seizure-induced neuronal damage and differentiation of regional severity of these alterations. Hippocampal neuropathology is slower and longer in duration (approximately 7 days), while the piriform cortex and amygdala exhibit very rapid neurodegenerative alterations (approximately 24 hours) after pilocarpine-induced status epilepticus. These histologic changes are reflected in opposing ADC values within these regions.
Insights
Diffusion-weighted imaging detects early seizure-induced neuronal damage. Changes in apparent diffusion coefficient (ADC) values reveal distinct regional damage patterns and severity following pilocarpine-induced status epilepticus.
Area of Science:
- Neuroscience
- Radiology
- Pathology
Background:
- Diffusion-weighted magnetic resonance imaging (DW-MRI) is a noninvasive technique for detecting regional neuronal damage.
- Pilocarpine-induced status epilepticus serves as a model to study seizure-induced pathophysiologic alterations.
Purpose of the Study:
- To investigate the correlation between changes in diffusion-weighted images and pathophysiologic alterations in pilocarpine-induced status epilepticus.
- To assess the utility of DW-MRI in identifying and differentiating the regional severity of seizure-induced neuronal damage.
Main Methods:
- In vivo T2- and diffusion-weighted MR imaging of brain tissues were performed at 3, 6, 12, and 24 hours post-pilocarpine administration.
- Histologic examination of brain tissues was conducted post-imaging to verify and quantify neuronal damage and cell death.
Main Results:
- Significant apparent diffusion coefficient (ADC) decreases were observed in the piriform cortex, amygdala, and retrosplenial cortex at 12 hours post-seizure.
- An increase in ADC was noted in the hippocampus at 24 hours post-seizure.
- Histology confirmed severe neuronal loss in the piriform cortex and amygdala, minimal damage in the retrosplenial cortex, and less pronounced hippocampal damage at 12 hours.
Conclusions:
- DW-MRI is a sensitive method for early detection of seizure-induced neuronal damage.
- Distinct patterns of ADC changes reflect regional differences in the time course and severity of neurodegeneration.
- Pilocarpine-induced status epilepticus causes rapid neurodegeneration in the piriform cortex and amygdala (approx. 24 hours), while hippocampal damage is slower and more prolonged (approx. 7 days).