Abstracts

Rationale: Vagus nerve stimulation (VNS) is now one of the standard palliative options for patients with medically refractory epilepsy. The latest devices including AspireSR (Model 106) and SenTiva (Model 1000) have capability to respond to ictal tachycardia. It is interesting whether or not the AutoStim Mode gives additional benefits to patients in terms of seizure frequency and severity of seizure events.

Methods: Patients who underwent replacement with the latest system and were treated by the author at an outpatient clinic were retrospectively reviewed. They had been treated with the former systems such as Demipulse (Model 103) or AspireHC (Model 105). These previous systems were replaced with AspireSR or SenTiva. Seizure frequency and the number of anti-seizure medications (ASMs) were extracted and compared before and after replacement of generators.

Results: Seventeen patients were identified. The mean age of seizure onset was 8.6 years old and the mean duration prior to the first VNS implantation was 15.4 years. They were treated with the former VNS systems for 4.5 years. The mean age at the time of generator replacement was 28.8 years old. Four out of 17 patients were under the age of 18. Seven patients underwent intracranial epilepsy surgery before these replacement.
Additional seizure reductions were obviously observed. The rate of seizure reduction with AspireSR or SenTiva running the AutoStim Mode was statistically significant (p=0.019). Six out of 11 patients who obtained less than a 50% seizure reduction or could not have any apparent seizure reduction by the former systems demonstrated additional seizure reductions. Only one patient did not show any benefits after replacement. The mean output current of the Normal Mode was 2.70 mA and the duty cycle was 31.4% before replacement. However, both of the parameters were obviously reduced to 2.06 mA and 11.8% respectively at the last observation. The mean output current of the AutoStim Mode was 2.26 mA. In addition, there was no significant change in the number of ASMs after replacement of generators.

Conclusions: VNS with the AutoStim Mode responding to ictal tachycardia may provide additional seizure reductions, even though patients cannot get satisfactory benefits with the former systems. Interestingly, the parameters such as the current output and the duty cycle may not necessarily be increased as we did with the former systems. Therefore, it would be reasonable to consider replacement of generators to the latest systems with the AutoStim Mode unless patients get satisfactory results with the former systems.
_x000D_ This study was approved by the internal ethics committee and published in Neuroscience Letters in 2020. Some more cases will be added for the presentation at this meeting.

Funding: There was no particular funding for this study and abstract.