Long-term vagus nerve stimulation in the treatment of Lennox–Gastaut syndrome
Introduction
Vagus nerve stimulation (VNS) is a relatively new nonpharmacological treatment for epilepsy. It was commercially introduced in the United States in 1997 as an adjunctive therapy ‘‘in adults and adolescents over 12 years of age with partial onset seizures, which are refractory to antiepileptic medications’’ [1].
The device offers an alternative treatment for patients with pharmacoresistant epilepsy. It has been tried on several different patient groups [2], [3], [4], [5], [6], and its effect has been shown to be comparable to that of newer antiepileptic drugs (AEDs); VNS has been demonstrated to be as effective as gabapentin, and slightly less effective than lamotrigine and tiagabine [7].
Lennox–Gastaut syndrome (LGS) is one of the most severe and prognostically unfavorable epileptic encephalopathies, and patients with this syndrome respond poorly to AEDs. Because of the multifocal character of LGS, resective surgery is unsuitable for patients with this syndrome. Nonpharmacological treatment methods include ketogenic diet, corpus callosotomy, and VNS. Several studies have evaluated the short-term effect of VNS on seizure frequency in patients with LGS [2], [3], [4], [5], [6]. Earlier studies focused solely on the reduction in total number of seizures, with the exception of one study in which the effects of VNS on drop attacks, complex partial seizures (CPS), and atypical absences were assessed [8].
The purpose of this study was to evaluate retrospectively the long-term effects of VNS on patients with pharmacoresistant LGS, with special emphasis on different seizure types and adverse effects.
Section snippets
Patient selection
Data were collected from the medical records of 30 patients who were implanted with a VNS generator in the period 1997–2007 at Oslo University Hospital—Rikshospitalet, Norway. All patients had been followed up at the National Centre for Epilepsy. The inclusion criteria in this open retrospective study were a confirmed electroclinical diagnosis of LGS according to the criteria of the International League Against Epilepsy [9] and an observation time of more than 12 months.
Diagnosis
The diagnosis was
Population
The study population consisted of 17 males and 13 females, 18 of whom were under 18 years. The median age at implantation was 13.0 years (4.0–52.0 years). Median age at onset of epilepsy was 1.1 years (0.1–7.0 years), and median duration of epilepsy before implantation was 11.9 years. The patients were observed for a median of 52 months (17–123 months).
Antiepileptic drugs
The median number of AEDs in use before implantation was 3.0 (2–4) and the patients had tried a median of 10.5 AEDs. The most frequently used
Discussion
The most important finding in this study was the overall positive effect and tolerability of VNS in patients with LGS. The strengths of this study are the relatively large population sample compared with other studies of LGS and the long follow-up time (median = 52 months). Other studies have indicated that the positive effects of VNS increase with time [2], [13], [14], and this is supported by the results of our study with a very high responder rate even after several years. These results are
Acknowledgments
The authors gratefully thank Karl Otto Nakken and Leif Gjerstad for their valuable comments on the article.
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