The influence of vagus nerve and spinal cord stimulation on the ictal fast ripple activity in a spike-and-wave rat model of seizures

OBJECTIVES: Fast ripple (FR) activity has received increasing attention as a potential epileptic marker. The current knowledge on how neurostimulation affects FRs is, however, very limited. In this study, we assess the influence of the vagus nerve stimulation (VNS) and spinal cord stimulation (SCS) frequency on ictal FRs associated with spike-and-wave (SW) seizures.

METHODS: SW discharges were induced and maintained by an infusion of pentylenetetrazol in rat. During ongoing SW seizures, SCS was conducted at 30, 80, 130, and 180 Hz and VNS at 10, 30, 80, 130, and 180 Hz. The FRs were derived from intracortical recordings and the FR rate was used for quantifying the level of FR activity.

RESULTS: The FR rate was significantly correlated (r = 0.81) with the level of total pentylenetetrazol dose. Compared with no stimulation intervals, SCS conducted at 80, 130, and 180 Hz significantly reduced the normalized FR rate by 24, 38, and 44%, respectively. Similarly, VNS conducted at 30, 80, 130, and 180 Hz significantly reduced the normalized FR rate by 23, 40, 61, and 65%, respectively.

CONCLUSIONS: In the present model of sustained SW seizures, the FR rate was proportional with the severity of the SW seizures. Both SCS and VNS attenuated the FR rate and this attenuation was consistently strongest at the higher stimulation frequencies. Our results suggest that SCS may induce some of the same antiepileptic effects as VNS.