Vagus nerve stimulation for drug-resistant epilepsy

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Vagus nerve stimulation for drug-resistant epilepsy: A European long-term study up to 24 months in 347 children

Source: Epilepsia, 55 (10): 1576 – 1584, 2014.
Authors: Iren Orosz, David McCormick, Nelia Zamponi, Sophia Varadkar, Martha Feucht, Dominique Parain, Roger Griens, Louis Vallée, Paul Boon, Christopher Rittey, Amara K. Jayewardene, Mark Bunker, Alexis Arzimanoglou & Lieven Lagae

Purpose:

to gain insight into the long-term impact of vagus nerve stimulation (VNS) in children (≤ 18 years of age) with drug-resistant epilepsy. The primary objective was to assess the change in seizure frequency of the “predominant seizure type” (defined as the most disabling seizure type).

Methods:

retrospective, open-label study conducted at 11 centres across the European Union.

Results:

347 patients were enrolled in this study; the stimulator was implanted between 28 April 1995 and 20 April 2010. At 12 months post-implantation 37.6% were responders (> 50% reduction of seizure frequency); 5.5% of them were seizure-free. 17.1% had a 25-49% reduction and 39.3% had a ≤ 25%. An increase in seizure frequency was reported in 6.1%. In a subset of patients seizure data were available at all time points (baseline, 6, 12 and 24 months). In this group an increasing response rate over time was seen: 33.2%, 40.0%, 44.2% at 6, 12 and 24 months respectively. In patients with available data on seizure severity, a decrease of seizure duration was found in 42.6%, 42.9% and 47.7% at 6, 12 and 24 months respectively. Efficacy in patients < 12  years of age was statistically significant compared to efficacy in patients ≥ 12. Quality of life assessment (QOL) showed improvement over time from 12 to 24 months of all QOL-factors. Regarding the clinician’s assessment of the patient’s over-all condition, 32.5% and 41.5% of patients were “much improved” or “very much improved” at 12 and 24 months. In post hoc analyses a statistically significant correlation between VNS total charge delivered by day and increase in response rate was found. Concerning safety issues 77 patients (22%) reported at least one treatment-emergent adverse event. In 30 patients convulsions were reported  but were not considered to be related to VNS. Lead damage was reported in 19 patients (5.4%), medical device change in 15 (4.2%), device removal in 13 (3.7%), device-related infection in 9 (2.5%), device-related complication in 6 (1.7%), dysphonia in 3 (0.8%) and issue related to device lead in 4 (1.1%).

Discussion:

the results presented here are comparable with the responder-rates from randomized-controlled trial of new anti-epileptic drugs. 38% of patients with VNS therapy were responders at 12 months. In a subset analysis of patients < 12 years efficacy was shown to be statistically better compared to > 12 years.

http://www.ncbi.nlm.nih.gov/pubmed/25231724

Comments reviewer, prof Van Nieuwenhuizen:

The demonstration of greater efficacy in a subset < 12 provides an important message as this finding will stimulate earlier application of this mode of therapy with even more efficacy. What is also important is the finding that VNS is effective in dramatic epilepsy syndromes such as Dravet and Lennox-Gastaut.

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