Nonlinear Dynamics of EEG in Pilocarpine-induced Status Epilepticus

ABSTRACT

BACKGROUND: Pilocarpine-induced status epilepticus (SE) model shows stereotypic EEG changes and behavioral characteristics. Although neuronal damages and therapeutic responses are also dependent on SE stages, the dynamical aspect of underlying neuronal interaction according to the SE stages has not been studied. We applied nonlinear analysis to the EEG recorded from pilocarpine-induced SE model to characterize nonlinear dynamics of different SE stage and to correlate therapeutic response with correlation dimension (D2). METHODS: Ten male Spraque-Dawley rats weighing 150-250g were used in this experiment. EEG was continuously recorded during SE and was classified into 6 stages as follows baseline (BS), transitional (TR), discrete seizure (DS), continuous ictal discharges (CID), early periodic epileptiform discharges (EP), and late periodic epileptiform discharges (LP). High dose diazepam (20 mg/kg) was injected at the LP stage. SEs of 5 rats (control group) was controlled by diazepam and those of the rest (failed group) were failed to stop status epilepticus. RESULTS: Mean D2 value decreased progressively with fluctuation and was significantly different for SE stage (df=5, F=11.594, p=0.000). Independent t-test showed that the difference of D2 value between the controlled and failed group was significant at CID (df=40, t=2.591, p=0.013) and LP stage (df=49, t=-2.425, p=0.019). CONCLUSIONS: These results suggest that nonlinear dynamical change at the late half of SE stage is one of the contributing factors determining therapeutic responsiveness in pilocarpine-induced SE model.