Vagal nerve stimulation in epileptic encephalopathies.

Abstract

Previous assessment of vagal nerve stimulation in the treatment of refractory epilepsy has been mostly in adults. Available results of this method in children are difficult to interpret because of various methodologic problems, especially the selection of implanted patients.The article in this issue by Parker et al1 and its addendum report encouraging results in a limited series of children with severe epilepsy of early onset fulfilling the criteria for epileptic encephalopathies also known as catastrophic epilepsies.Although the efficacy of vagal nerve stimulation appeared initially modest, such results were nonetheless of interest, given the poor therapeutic results and outcome of the epilepsy syndromes treated. The improvement of results after 2 years of treatment is all the more remarkable because the overall efficacy of most therapies of difficult-to-treat epilepsies tends to wear out with time. In contrast, the median percentage of seizure reduction compared with baseline level became significant in the patients of Parker et al while no aggravation was observed. The fact that 1 child became seizure-free and 5 had a >60% decrease in seizure frequency is of practical significance in such a severe disorder. These results strongly support the conclusion that vagal nerve stimulation in children with epileptic encephalopathies may be a useful adjunct to antiepileptic agents in these syndromes.Although this was a prospective study, it was uncontrolled and factors other than vagal stimulation, including placebo effects, may have been in part responsible for the results. The strength of this work is that, in contrast with many previous reports, the patients included were precisely defined and classified into epilepsy syndromes according to the classification of the International League Against Epilepsy. This is an essential point, as all too often various types of epilepsy are mixed, making the significance of the results almost impossible to assess. Also, all patients were carefully studied, a surgically treatable lesion was excluded, and considerable efforts were made to avoid bias in recording of seizures, to maintain other treatments unchanged, to use similar stimulation parameters, and, importantly, to begin stimulation after a reasonably long baseline period. Although some departures from these principles occurred, they appear unlikely to have seriously biased the results. Unfortunately, vagal stimulation had no detectable effect of cognitive function although carers subjectively perceived the result of treatment as positive. The electroencephalogram was also unchanged.Clearly, vagal nerve stimulation has a long way to go in terms of giving a definitive answer to the challenge of severe early-onset epilepsies as it is only partly effective and not devoid of risks. It requires a surgical operation with possible complications as in 1 patient of this study. However, it is probably worth trying when drugs have failed and surgery is not possible.