Vagus Nerve Stimulation (VNS): Efficacy of Standard Stimulation Versus Rapid Cycle- A Randomized Controlled Trial.
Abstract number :
3.205
Submission category :
Year :
2001
Submission ID :
2958
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
J.M. Scherrmann, MD, Epileptology, University of Bonn, Bonn, Germany; C. Hoppe, Epileptology, University of Bonn, Bonn, Germany; S. Kuczaty, MD, Epileptology, University of Bonn, Bonn, Germany; R. Sassen, MD, Epileptology, University of Bonn, Bonn, German
RATIONALE: VNS gained increasing acceptance as add-on therapy for drug-resistant epilepsies. Two different stimulation methods are acknowledged to be effective in epilepsy therapy: Standard stimulation and Rapid cycle. Up to now there are different opinions concerning responder rates in both groups. The following analysis was performed in order to compare efficacy of standard stimulation and rapid cycle. The efficacy of both stimulation strategies was evaluated in two studies: An open clinical follow up study(1) and a prospective randomized controlled trial(2).
METHODS: Study 1: Open clinical trial. From February 1998 to December 1999, 71 patients were implanted with the NCP-System for VNS and first treated with standard parameters (off-time: 5 min.; on-time: 30 sec.). In case of non-response after six to nine months of treatment, parameters were changed to a rapid cycle stimulation (off-time 12 sec.; on-time 7 sec.).
Study 2: A randomized controlled study. From January 2000 to December 2000, 41 patients were randomly allocated to standard or rapid cycle (off-time: 30 sec.; on-time: 7 sec.) by unbiased alternation from the beginning. The responder rate with response defined by [gt] 50% seizure frequency reduction was used as outcome measure.
RESULTS: Study 1: Patients implanted between 1998 and 1999 and switched to rapid cycle conditions because of non-response showed a [gt]50% improvement of seizure frequency in 31% of the cases and moreover a 15-49% reduction in 26%, whereas 44% of the patients did not profit by changing the stimulation cycles.
Study 2: Those patients in the randomized controlled trial treated with standard parameters showed a responder rate of 25%, whereas patients under rapid cycle conditions showed a responder rate of 39%. This difference approached statistical significance.
CONCLUSIONS: In case of non-response to standard stimulation at the beginning of VNS the change to rapid cycle stimulation after 6-9 months can improve the seizure frequency in 56% of the patients.
These preliminary results of the randomized controlled study indicate some advantage for rapid cycle conditions from VNS start of treatment. However, the findings are not significant so far, probably due to the small sample size. Therefore the study is continued.