Low frequency stimulation decreases seizure frequency in a rat model of temporal lobe epilepsy

Cortical stimulation for the treatment of epilepsy is currently being studied in both animals and humans; however, because the mechanisms are not well understood, optimal stimulation parameters and target have yet to be been determined. This paper describes the effects of low frequency stimulation (LFS) using a novel target, the hippocampal commissural fibers, in a rat model of human mesial temporal lobe epilepsy (MTLE). Epilepsy was induced in adult Sprague-Dawley rats (n=7) by one single electrical stimulation episode of the amygdala. After a three month period of epileptogenesis, baseline spontaneous seizure frequency was determined by continuous video and electrographic monitoring of the bilateral hippocampi for 2 weeks. Then, LFS (1 Hz) was applied continuously for 60 minutes ON and 15 minutes OFF, for two weeks, and the mean seizure frequency before, during and after treatment were compared. A statistically significant difference (p = 0.008) between the baseline and treatment states was observed. In 7 animals, 90% decrease in seizure frequency was observed during treatment and a 57% decrease in seizure frequency during the period following treatment when compared to the seizure frequency before stimulation. These findings support the hypothesis that the hippocampal commissures may be an effective target in low frequency stimulation for the suppression of spontaneous seizures in mesial temporal lobe epilepsy.