Diffusion-weighted imaging in kainic acid-induced complex partial status epilepticus in dogs

OBJECTIVE: To investigate diffusion-weighted imaging (DWI) in status epilepticus, a canine model of kainic acid (KA)-induced complex partial status epilepticus (CPSE) was produced. In order to validate its usefulness, MR imaging was carried out at various times following onset of CPSE followed by histopathology. MATERIAL AND METHODS: Six normal dogs were used in this study. In each dog, a cannula was stereotactically inserted into the left amygdala. One week after surgery, all dogs were imaged at MRI. Pre-injection imaging consisted of T2 weighted (T2W) imaging, fluid attenuated inversion recovery (FLAIR), and DWI. Two weeks after surgery, five dogs received intraamygdaloid KA microinjections. One dog was used as a control. MRI was carried out at 3, 6, 12, 24 and 48 h after onset of CPSE. Animals were euthanized immediately after MRI for histopathological evaluation. The average of each apparent diffusion coefficient (ADC) in the regions of interest was calculated from each DWI. RESULTS: At 3 and 6 h, DWI hyperintensity and low ADC were found in the injected amygdala, without any T2W and FLAIR imaging changes. At 12 and 24 h, all imaging showed hyperintensity with higher ADC in the amygdala and the hippocampus. At 48 h, all imaging techniques showed continued hyperintensity, but ADC showed a trend towards normalization. This increasing hyperintensity in DWIs were in agreement with the degree of histopathology during CPSE. SUMMARY: This study suggests that DWI is a useful imaging method for finding the epileptic focus or for examining potential epileptic brain damage in status epilepticus.