Abstracts

RATIONALE: Vagus Nerve Stimulation (VNS) is an approved treatment for partial epilepsy in those 12 years and over. No experience is documented on antiepileptic drug (AED) use during long-term VNS therapy. METHODS: A retrospect chart review was conducted on (N=40) patients during the pre and post implant period. Records were reviewed for alterations in the number of AEDs at 3 month intervals of time. Seizure history, VNS side effects, and long term changes in VNS therapy were also analyzed.RESULTS: There were N=35 patients evaluable after at least 6 months of VNS therapy. Age ranged from 3-57 years. The number of AEDs ranged from 1 to 4. There were 18 with a developmental disability and 10 with Lennox Gastaut. VNS treatment ranged from 0.5 to 3 years. Few AED changes were made during the first three months post implant. (N=2) of the group required AED dose alterations due to a sub or supra therapeutic serum level during this early implant phase, when stimulation parameters were typically adjusted. Once optimal VNS settings were reached, AED changes were made in response to seizure occurrence. The number of prescribed medications was decreased in N=2 (5%), due to improved seizure frequency. Medications were added in N=12 (33%) due to seizure exacerbation or an increase in frequency. Medication additions all involved recently markeded AEDs not available to these patients at the time of implant. N=18 (51%) did not have any decrease in the number of AEDs prescribed due to improved seizure control. N=20 (57%) patients had improved seizure control characterized by over 33% reduction in the average monthly occurrence, while only N=2 (5%) had the number of AEDs reduced. A small group of N= 5 (14%) patients requested to end VNS therapy after 1 to 2 years in spite of AED adjustments. CONCLUSIONS: A varied pattern of AED use with VNS was noted over time. AED additions to patient medication regimes were directly correlated to decreased efficacy of VNS. No changes were made in the AEDs during the first 3 months of VNS. Thereafter no clear pattern or type of AED change was identified, other than the availability of newly marketed AEDs for improved seizure control. A decrease in the number of AEDs prescribed was not directly correlated with improved seizure control over time.