Seizure abatement with single dc pulses: is phase resetting at play?

Topological approaches for seizure abatement have received scarce attention. The ability to reset the phase of biological oscillations has been widely exploited in cardiology, as evidenced in part by the usefulness of implantable of defibrillators, but not in epileptology. The aim of this work is to investigate the feasibility of seizure blockage using single or brief monophasic (DC) pulse trains. Single DC or brief (0.1 s) pulse trains were delivered manually or automatically to generalized seizures, induced in rats with the convulsant 3-mercaptoprionic acid, a GABA inhibitor. Treatment outcome (blocked vs. not blocked seizures) was ascertained visually and correlated with the "rhythmicity index", an indirect estimate of neuronal synchrony level. Blockage using single or brief (0.1 s) DC pulses was consistently achieved for seizures with a rhythmicity index > 0.6, while seizures with levels <0.6 were not, although transient phase changes in their oscillations were effected. This work reveals that level of neuronal synchronization may be an important factor in determining the probability of seizure blockage. Seizure blockage using single or brief DC pulse trains and its effects on neural tissue merit further investigation. The clinical applicability of this therapeutic modality and means to enhance it are discussed.