Response of status epilepticus induced by lithium and pilocarpine to treatment with diazepam

Status epilepticus (SE) was induced in rats by administration of 3 mmol/kg lithium chloride followed 24 h later by injection of 25 mg/kg pilocarpine. Treatment with 20 mg/kg diazepam was initiated at the time each of four EEG patterns was seen: (i) discrete electrographic seizures; (ii) waxing and waning epileptiform activity; (iii) continuous, high-amplitude, rapid spiking; and (iv) periodic epileptiform discharges (PEDs) on a relatively flat background. Success of diazepam in stopping all seizure activity was predicted by the EEG pattern seen at the time of treatment. All rats treated while displaying discrete electrographic seizures had status stopped with diazepam, but only three of six with waxing and waning epileptiform activity and one of six each with continuous spiking and PEDs. Rats which continued to seize had a decrease in spike amplitude of 74.8 +/- 18.25% following diazepam injection. These data confirm the clinical impression that the longer the duration of status epilepticus, the more difficult it is to control and suggest that the EEG pattern at the time of treatment predicts the probability of success.