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

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