Rapid titration of VNS therapy reduces time-to-response in epilepsy.

BACKGROUND: Common titration strategies for vagus nerve stimulation (VNS) prioritize monitoring of tolerability during small increases in stimulation intensity over several months. Prioritization of tolerability is partially based on how quickly side effects can be perceived and reported by patients, and the delayed onset of clinical benefits from VNS. However, many practices assess the clinical benefit of VNS at one year after implantation, and excessive caution during the titration phase can significantly delay target dosing or prevent a patient from reaching a therapeutic dose entirely. OBJECTIVE: This study aimed to characterize the relationship between titration speed and the onset of clinical response to VNS. METHODS: To assess differences between more aggressive titration strategies and more conservative ones, we analyzed the relationship between time-to-dose and time-to-response using a weighted Cox regression. The target dose was empirically defined as 1.625 mA output current delivered at 250 microsecond pulse widths at 20 Hz. Patient-level outcomes and dosing data were segregated into fast (<3 months), medium (3-6 months), and slow (>6 months) cohorts based on their titration speed. RESULTS: The statistical model revealed a significant relationship between titration speed and onset of clinical response, defined as a 50% reduction from baseline in seizure frequency. Frequency of adverse events reported between each cohort trended toward higher rates of adverse events in adults who were titrated quickly; however, the pediatric population appeared to be more tolerant of titration at any speed. CONCLUSIONS: This analysis indicates that faster titration yields faster onset of clinical benefit and is especially practical in the pediatric population, though attempts to accelerate adult titration may still be warranted.

VNS parameters for clinical response in Epilepsy.

BACKGROUND: While vagus nerve stimulation (VNS) has been in use for over two decades, little professional guidance exists to describe dosing and titration of therapy which is the consequence of a limited amount of evidence developed during the pre-market phase of therapy development. Post-market surveillance of dosing practice has revealed significant deviations from dosing and titration guidance offered by professional societies as well as the manufacturer. OBJECTIVE: This analysis aims to identify a target dose for VNS Therapy in Epilepsy. METHODS: Herein, VNS clinical outcomes are linked to the patient-specific dosing parameters for each study visit (n = 1178 patients). A generalized linear mixed model was built to ascertain the relationship between key stimulation parameters (i.e., Output Current, Pulse Width, Signal Frequency, and Duty Cycle) and clinical response, defined as a 50% or greater reduction in seizure frequency from baseline. Other demographic parameters of interest, such as duration of epilepsy and age at implant, were also explored. RESULTS: A population level target output current and duty cycle for VNS therapy for epilepsy was identified as 1.61 mA and 17.1% duty cycle. Patients with shorter duration of epilepsy were identified to have a higher likelihood to respond to VNS therapy (p < 0.001). While patients who were on the therapy longer were more likely to respond to the therapy, the effect did not interact with the dosing settings - suggesting that patients who have been chronically underdosed may still benefit from achieving the target dose. CONCLUSION: An opportunity exists to improve upon VNS outcomes by aligning clinical practice around this evidence-based target dose.