Purpose: To retrospectively review our experience with VNS in pediatric patients with pharmacoresistant epilepsy and examine the seizure-frequency outcome and rates of discontinuation in two age groups: adolescent and pre-adolescent children.
Results: Complete pre- and post-VNS data were available for 46/49 patients. Median age at implantation was 12.1 (range 2.3-17.9) and median duration of epilepsy 8.0 (1.9-16.9) years. Twenty-one patients (45.6%) were under 12 years at the time of surgery. Median follow-up was 2 years; follow-up exceeded 4 years in 9/46 patients. As compared to baseline, median seizure-frequency reduction in the setting of declining numbers was 56% at 3 months, 50% at 6, 63% at 12, 83% at 24 and 74% at 36 months. When a last observation carried forward analysis was employed median seizure-frequency reduction in the range of 60% was observed at 1, 2 and 3 years post-VNS. Twenty patients (43.5%) had >75% seizure-frequency reduction. No response (increase or <50% reduction) was observed in 19/46 (41.3%). Five patients (10.1%) were seizure-free for more than 6 months by their last follow-up. There was no difference in the number of AEDs used before and after VNS. The long-term discontinuation rate was 21.7% and reflected a lack of clinical response or infection.
Conclusions: In this series VNS was well-tolerated and effective as add-on therapy for refractory seizures in children of all ages. Response was even more favorable in the younger group (<12 years at implantation). Infection and lack of efficacy were the most common reasons for discontinuation of long-term VNS therapy in this group.