[ldquo]RAPID CYCLING[rdquo] OF VAGUS NERVE STIMULATORS (VNS) MAY WORSEN SEIZURE CONTROL
Abstract number :
2.438
Submission category :
Year :
2003
Submission ID :
3649
Source :
www.aesnet.org
Presentation date :
12/6/2003 12:00:00 AM
Published date :
Dec 1, 2003, 06:00 AM
Authors :
Sunila E. O[apos]Connor, Maria S. Chico, Angela N. Song, D. Larkin Mitchell, Charles J. Marcuccilli, Michael H. Kohrman, Wim van Drongelen, Kurt E. Hecox Pediatric Epilepsy Center, University of Chicago, Chicago, IL
The use of vagus nerve stimulators (VNS) has been shown to be an effective, safe and durable treatment of pharmacoresistent epilepsy. Despite this fact, choosing the ideal stimulator setting for each patient can be challenging. We present the outcomes of nine patients with VNS placed on [ldquo]rapid cycling[rdquo] in an attempt to obtain optimal seizure control. Improvement or worsening can be operationalized by clinical seizure counts, electrographic changes or both. Electrographic analysis can be quantitative (e.g. dynamical systems measures) or qualitative (e.g. spike counts). We have applied both measures to this patient population.
Nine patients with VNS were changed from their current settings to [ldquo]rapid cycling[rdquo] in an attempt to better control seizures. [ldquo]Rapid cycling[rdquo] was defined as repetitive stimulation lasting 7 seconds followed by twelve seconds of off time. All patients were monitored with video EEG one hour prior to, during and 1 to twenty-four hours after setting changes. Each patient had a baseline spike frequency, seizure frequency, Kolmogorov Entropy, correlation dimension, Eigenvalue and global measure of non-linearity (Z). Three artifact free samples of thirty seconds each were used for calculation of the quantitative dynamic systems measures. Comparisons were then made between pre and post VNS setting changes.
Mean patient age was 10.8 years (range 2 [ndash] 24). Changing of VNS settings to [ldquo]rapid cycling[rdquo] produced worsening in terms of clinical seizures and quantitative measures in 4/9 (45%) patients. These effects were recognized by simultaneous EEG monitoring within one hour of [ldquo]rapid cycling[rdquo]. Of the remaining patients, 2/9 (22%) improved and 3/9 (33%) remained stable with VNS setting changes.
Nearly one-half of VNS patients placed on [ldquo]rapid cycling[rdquo] to improve seizure control showed dramatic worsening in terms of clinical seizures and quantitative EEG measures. EEG monitoring identified these patients in less than one hour. Thus it is possible to detect and avoid this undesirable outcome. To our knowledge, these short-term changes have not been reported and quantified previously. As a result, we recommend that VNS patients who undergo setting changes to [ldquo]rapid cycling[rdquo] should have concomitant EEG monitoring to identify worsening.
[Supported by: Cyberonics]