Abstracts

The efficacy of the vagal nerve stimulator (VNS) in treating patients with refractory partial epilepsy has been well demonstrated. However, its use in patients with refractory primary generalized epilepsy has not been studied fully. This is a retrospective study to evaluate the efficacy of VNS in this patient population. 102 patients were followed in the VNS clinic at the University of Utah Hospital in September of 2003. Of these 102 patients, 13 had refractory primary generalized epilepsy and had VNS implanted from 2000 to 2003. The diagnosis of primary generalized epilepsy was based on the clinical history, physical examination, magnetic resonance imaging (MRI) and electroencephalography (EEG) data. Patients with mental retardation were excluded from the study. The clinic notes of the 13 patients were reviewed. Clinical information including age of seizure onset, seizure frequency, number of antiepileptic drugs (AED) and VNS parameters at the time of VNS implantation, 6, 12 and 24 months afterwards, when available, was collected. Six months after implantation, 6/13 (46.15%) of patients had reduction in frequency of generalized tonic-clonic (GTC) seizures, while 3/13 (23.08%) had no change and 4/13 (30.77%) had increase in the frequency of GTC seizures. For those who had GTC seizure reduction, the average decrease in seizure frequency was 72.4%. At 12-month post-implantation, in 10 patients with available data, 6 (60%) had reduction, while 2 (20%) had no change and 2 (20%) had increase in GTC seizure frequency as compared to the pre-implantation baseline. For those who showed reduction in GTC seizure frequency, the average reduction was 81.35%. At 24-month post-implantation, in 9 patients with available data, 7/9 (77.78%) had reduction, 1/9 (11.11%) had no change and 1/9 (11.11%) had increase in GTC seizure frequency. For those who experienced seizure reduction, the average decrease in GTC seizure frequency was 84.04%. The number of AEDs at 24-month post-implantation was reduced in 4 out of 9 (44.44%) patients, unchanged in 3 patients and increased in 2 patients. However, AEDs were added in those 2 patients for headache and mood stabilization. VNS is effective in reducing GTC seizure frequency in 46% to 78% patients with medically refractory primary generalized epilepsy. It also helps to reduce the number of AEDs that patients require.