A Systematic Study of the Effects of Vagus Nerve Stimulation Current Intensity on EEG and ECG
Abstract number :
1.139
Submission category :
Year :
2001
Submission ID :
633
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
A.L. Paige, M.D., Neurology, Yale University School of Medicine, New Haven, CT; J.L. Thompson, M.D., Neurology, Yale University School of Medicine, New Haven, CT; H.P. Zaveri, Ph.D., Neurology, Yale University School of Medicine, New Haven, CT; H. Patwa,
RATIONALE: Vagus nerve stimulation (VNS) is an effective antiepileptic therapy with an unknown mechanism of action. Clinical trials have demonstrated greater effectiveness of a high stimulus current intensity compared to a low current intensity supporting the importance of the role of current intensity in VNS. However, the ideal VNS settings for any inividual are unclear. We wished to define a dose response curve for stimulus current using EEG & ECG parameters including spectral analysis, spike and slow wave counts and assessment of the R-R interval.
METHODS: Scalp EEG was recorded from eight VNS-implanted partial epilepsy patients using 26 electrodes (10-20 system plus three subtemporal leads bilaterally), as well as, ECG, eye and left neck leads. Four minute epochs of EEG were recorded during quiet wakefulness (eyes open) at each of nine current settings. Stimulus frequency, duration and pulse width were held constant at 30 Hz, 30 seconds and 500 microseconds, respectively. The following current settings were assessed: 0.25, 0.5, 0.75, 1.0, 1.25, 1.5, 2.0, 2.5 and 3.0 mA as tolerated. We counted spikes and slow waves, performed spectral analysis and calculated R-R intervals at each of the stimulus settings compared to baseline.
RESULTS: There were stimulus-related changes in all measures with the more robust changes seen in delta power and total power on spectral analysis. There were changes (increases and decreases from baseline) in spike and slow wave counts, as well as R-R intervals that varied from patient to patient.
CONCLUSIONS: VNS is an effective new treatment for epilepsy; however, optimal stimulus settings have not been determined and may differ among patients. This systematic analysis demonstrated stimulus current related changes in both the EEG and ECG. However, the changes varied from patient to patient in both direction and magnitude. Certain EEG parameters may have potential as surrogate markers that allow determination of ideal VNS settings for the individual patient. Furthermore, EEG analysis may help elucidate the mechanism(s) of VNS effects on seizures and perhaps, depression and recognition memory.
Support: Cyberonics, Inc.
Disclosure: Grant - Cyberonics, Inc.