Vagal Nerve Stimulation: Efficacy of Standard Versus Rapid Cycling
Abstract number :
2.324
Submission category :
Year :
2001
Submission ID :
2908
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
B. Brozman, M.D., Department of Neurology, University of Miami School of Medicine, Miami, FL; W.O. Tatum, M.D., Department of Neurology, University of South Florida, Tampa, FL; J.A. Ferreira, M.D., Tampa, FL; J.D. Slater, M.D., Springfield, MO; D.K. Narit
RATIONALE: Vagal nerve stimulation is an established method of treatment of medically intractable epileptic seizures. Clinical trials demonstrated good efficacy using what has been called standard stimulation pattern (on-time 30 s, off-time 5 min.). Nevertheless, good results were also reported with a sequence called rapid cycling (on-time 7 s, off-time 0.3 min.). Both protocols are being used clinically but no controlled comparison has been done. This study assesses the efficacy of both stimulation protocols.
METHODS: The study is a single-blinded parallel randomized trial. Patients with intractable epileptic seizures that underwent implantation of the vagal nerve stimulator were randomized into a standard or rapid cycling group. Stimulus frequency was 30 Hz and output current was increased as tolerated to a setting of 1-4 mA. Post-implantation seizure characteristics followed for 3-12 months were compared to the 3-month pre-implantation data. The efficacy defined as seizure rate reduction was compared between the two groups.
RESULTS: Twenty-eight patients were enrolled. Thirteen patients were randomized to standard and 15 to rapid cycling. The age range was 4-58 years with the mean age of 29.1 years. Age of seizure onset was 0.6-31 years with the mean age of 12.8 years. The length of follow-up so far has ranged 2-12 months with average of 8.12 months. The rapid cycling showed lower efficacy in the first 3 months of stimulation (see table). Thereafter, seizure reduction was similar in the two groups (approx. 50%). Seizure frequency improved even more in the standard cycling group at months 9-12 but results may be skewed by the small number of patients followed in that group.
CONCLUSIONS: Both stimulation protocols produce approximately the same reduction of the seizure rate. The exception is the first 3 months of stimulation where standard cycling seems to show better efficacy. Relatively small number of patients followed at month 12 may account for the observed difference during months 9-12. Lack of superiority of rapid cycling over the standard stimulation may render this method less advantageous due to its effect on shortening of the stimulator battery life span. Further patients need to be studied to compare efficacy in different seizure types.[table]
Disclosure: Consulting - Cyberonics Inc.; Honoraria - Cyberonics Inc.