A prospective long-term study on the outcome after vagus nerve stimulation at maximally tolerated current intensity in a cohort of children with refractory secondary generalized epilepsy

Abstract

Introduction: We report the outcome after vagus nerve stimulation (VNS) in children with secondary generalized epilepsy.

Methods: Twenty-four consecutive children with Lennox-Gastaut or Lennox-like syndrome under the age of 12 years by the time of surgery, who were implanted with a vagus nerve stimulator and had at least two years of postimplantation follow-up, were prospectively included in the study. The generator was turned on using 0.25 mA, 30 Hz, 500 μsec, 30 sec "on," 5 min "off" stimuli parameters; current was then increased by 0.25 mA every two weeks, until 3.5 mA was reached or adverse effects were noted.

Results: Magnetic resonance imaging was normal or showed atrophy in 13 children. Six children got an end-of-study (24 months) postimplantation video-electroencephalogram, and their findings were similar to those before VNS. Quality of life and health measures improved in up to 50% (mean = 25%) in 20 children. Attention was noted to improve in 21 out of the 24 children. Final intensity parameters ranged from 2 to 3.5 mA (mean = 3.1 mA). An implantation effect was noted in 14 out of the 24 children, and lasted a mean of 20.2 days. There were 47 seizure types among the 24 children. An at least 50% seizure frequency reduction was noted in 35 seizure types and 17 seizure types disappeared after VNS. Atypical absence, myoclonic and generalized tonic-clonic seizures were significantly reduced by VNS; tonic and atonic seizures did not improve. Transient seizure frequency worsening was noted in ten of the 24 children, at a mean of 3.1 mA.

Discussion: Our study showed that VNS was effective in reducing atypical absence, generalized tonic-clonic, and myoclonic seizures (but not atonic or tonic seizures) in children with Lennox-Gastaut or Lennox-like syndrome. A concomitant improvement in attention level and quality of life and health also was noted. Secondary generalized epilepsy represents a subset of good candidates for VNS.

Keywords: Children; VNS; generalized epilepsy; outcome; stimulation.