Abstracts

RATIONALE: Vagus nerve stimulation (VNS) has been shown to be effective treatment for partial-onset seizures. Several case studies in the literature have shown its efficacy in symptomatic generalized epilepsy, mostly Lennox-Gastaut syndrome. Its effectiveness in primary generalized epilepsy, especially absence seizures has not been reported. The aim of this study is to report the effectiveness and tolerability of VNS in patients with refractory absence seizures.
METHODS: A retrospective chart-review of three patients with refractory absence seizures implanted with VNS was carried out. IRB approval for the study was obtained. They had failed treatment with 3 or more antiepileptic drugs known to be effective in absence seizures. Patients had several routine EEG recordings; 2 of the 3 subjects also had prolonged EEG-video monitoring. All patients showed the typical generalized 3Hz spike-wave complexes. MRI scans were of all three patients were normal. Doses of concurrent antiepileptic drugs were not altered following VNS implantation. Postoperative follow-up ranged from 5 months - 2 years (mean 15.7 months).
RESULTS: Patients ranged in age from 10-17 years (mean 14.3 years). Their seizures began between 5 and 11 years of age (mean 8.3 years). Seizures occurred between 20-50 times a day in all subjects. All had failed standard therapy for absence seizures including valproic acid, ethosuximide, lamotrigine, topiramate used to maximally tolerated levels. One patient also failed Zonisamide. Two of the three patients also had generalized tonic-clonic seizures. Their neurologic examinations were normal and they had normal IQ. Two patients experienced a [gt]75% reduction and the third patient had a 90% seizure reduction in absence seizures. A similar reduction was also noted for generalized tonic-clonic seizures. Side effects consisting of hoarseness and throat discomfort was mild in all three and were minimal by 3 months.
CONCLUSIONS: In our three subjects with refractory absence seizures, VNS produced [gt]75% seizure reduction in all three patients. During the follow-up period, we did not observe any loss of efficacy or significant side effects. VNS is a promising therapy for refractory absence seizures.