POSTICTAL ALTERATION OF SODIUM CONTENT AND APPARENT DIFFUSION-COEFFICIENT IN EPILEPTIC RAT-BRAIN INDUCED BY KAINIC ACID

Purpose: We studied temporal changes of brain sodium and apparent diff usion coefficient (ADC) in a temporal lobe epilepsy (TLE) rat model us ing kainic acid (KA). Methods: In situ three-dimensional Na-23 magneti c resonance imaging (MRI) and proton diffusion-weighted imaging (DWI) were used. KA at a dose of 10 mg/kg body weight and 12 adult Sprague D awley rats weighing 228-318 g (268 +/- 25 g) were used. Results: Twent y-four hours after KA injection, magnetic resonance (MR) visible sodiu m levels increased in both the pyriform cortex (+90%) and amygdala (+6 8%) and increased insignificantly in the hippocampus (+18%) and caudat e-putamen (12%). The ADC in the pyriform cortex showed a -9% decrease at 5 h postictally, reaching -30% at 24 h, whereas in the amygdala dec reases were -8 and -26% respectively. A significant decrease in ADC (- 7%) in the hippocampus was also observed 24 h postically. Seven days l ater, sodium increases persisted, whereas ADC returned to normal level . Conclusions: The increase in MR visible sodium, associated with the decrease in ADC is consistent with the hypothesis that sequential seiz ures caused an increase in sodium influx and perturbation of membrane ion homeostasis, which eventually evolved into an irreversible phase o f cellular edema, with increased MR visible intracellular sodium and d ecreased ADC. Return of ADC to near-control level and persistent high sodium level at 7 days may be explained by the increase in extracellul ar space and tissue necrosis.