Long-term vagus nerve stimulation in the treatment of Lennox-Gastaut syndrome
The long-term effects of vagus nerve stimulation (VNS) on seizure frequency were studied in 30 patients with Lennox-Gastaut syndrome. Median observation time was 52 months (17-123). The effect parameters investigated were total number of seizures and different seizure types. The median reduction in number of seizures was 60.6%. The effects of VNS varied considerably between seizure types. Best effects were observed with atonic seizures (80.8% median reduction, number of responders: 8/12), followed closely by tonic seizures (73.3% median reduction, number of responders: 8/13). Least effects were with generalized tonic-clonic seizures (median reduction 57.4%, number of responders: 11/20). Additional positive effects included milder or shorter ictal or postictal phase in 16 patients. Improved alertness was reported in 76.7%. Adverse effects, of which drooling and voice alteration were most frequent, were reported in 20 patients. There was a statistically significant reduction in the median number of antiepileptic drugs used. The discontinuation rate was 16.7%.