Reducing VNS stimulation parameters: Is it safe?

Introduction Vagal nerve stimulation (VNS) is an adjuvant therapy used in the treatment of patients with refractory epilepsy who are not candidates for resective surgery or who have limited results after surgical procedures. Currently, there is enough evidence to support its use in patients with various types of epilepsy. Therefore, the present study was conducted to explore the possibility of optimizing therapy by reducing the consumption of the system's battery. Methods The prospective and double-blind analysis consisted in the evaluation of 6 patients submitted to VNS implantation for 3 months, followed by adjustment of the stimulation settings and continuity of follow-up for another month. The standard protocol was replaced by another with a frequency value of 20 Hz instead of 30 Hz to increase battery life. The safety of this procedure was evaluated through the assessment of two main variables: seizures and side effects. Results The stimulation at 20 Hz showed 68% reduction in the incidence of seizures (p»0.054) as well as low incidence of side effects. Conclusion The present study suggests that the reduction of the stimulation frequency from 30 to 20 Hz is a safe procedure, and it does not compromise the effectiveness of therapy.

Estimulación crónica intermitente del nervio vago en el tratamiento de epilepsia refractaria: experiencia en México con 35 casos / Chronic intermittent vagal nerve stimulation in the treatment of refractory epilepsy: experience in Mexico with 35 cases

Introducción: El papel de la estimulación crónica intermitente del nervio vago (ECINV) en el tratamiento de la epilepsia refractaria está evolucionando y requiere precisarse mediante la descripción de resultados, efectos adversos y complicaciones en poblaciones específicas. Material y métodos: Se seleccionaron los pacientes con epilepsia refractaria sometidos a ECINV con mínimo 12 meses de seguimiento, utilizando estadística descriptiva e inferencial para valorar el efecto sobre la frecuencia e intensidad de las crisis, memoria, ánimo, estado de alerta, recuperación postictal y calidad de vida (escala subjetiva, cuestionario QoLIE-31), y los factores (sexo, edad, tiempo de evolución, número/tipo crisis, parámetros de estimulación) asociados a la respuesta clínica. Se describen los parámetros de estimulación usados, empleo del magneto, complicaciones y efectos adversos. Resultados: Se seleccionaron 35 pacientes, edad de cinco a 48 años, 18 con epilepsia parcial, 17 con generalizada. No hubo complicaciones, infección o alteración de la cicatrización en los procedimientos quirúrgicos. La reducción promedio en crisis fue de 55.65 % (p < 0.001). En epilepsias generalizadas hubo 58.8 % de respondedores y 88.9 % en parciales. Cuatro sujetos presentaron mejoría > 90 %, con control total; en dos pacientes aumentó la frecuencia de las crisis. La respuesta al tratamiento fue buena subjetivamente en 33 pacientes. La calificación global de QoLIE-31 aumentó 12.6 puntos (p = 0.020). Solo el tipo de crisis se asoció con la respuesta clínica. Los efectos adversos fueron transitorios y respondieron al cambio de parámetros de estimulación. Conclusiones: la ECINV es segura, bien tolerada y eficaz para el tratamiento paliativo en casos seleccionados de crisis parciales y generalizadas multifocales refractarias.

BACKGROUND: The role of vagal nerve stimulation (VNS) in the treatment of refractory epilepsy is still evolving and requires precision through extensive description of acute and chronic results, adverse effects and complications in specific populations. METHODS: We selected patients with refractory epilepsy subjected to VNS who had completed at least a 12-month followup. Descriptive and inferential statistics were used to review and assess the effects of VNS on seizure frequency/intensity, memory, alertness, mood, postictal recovery, and quality of life (subjective scale, QoL IE-31 inventory) as well as factors (gender, age, age of onset, time of surgery, stimulation parameters, seizure frequency and type) associated with clinical response. We describe stimulation parameters, complications and adverse effects compared to other series. RESULTS: We selected 35 patients with an age range of 5-48 years; 18 patients presented partial epilepsy and 17 generalized epilepsy. All procedures and wound healing were uneventful, and no infections were reported. Median reduction in seizure frequency was 55.65% (p <0.001). Four patients showed improvement of >90%. Two patients became seizure free, whereas seizure frequency increased in two patients. The subjectively qualified response to treatment was good in 33 patients. The mean global increase in the QoLIE-31 Scale was 12.6 (p = 0.020). Improvements in memory, mood, alertness and postictal recovery period were documented. Only seizure type showed statistically significant association with clinical response. Adverse effects were transitory and responded to changes in stimulation parameters. CONCLUSIONS: VNS is a safe, feasible, well-tolerated and effective palliative treatment in appropriately selected cases of refractory partial and multifocal generalized seizures.