LONG-TERM EFFICACY WITH VAGUS NERVE STIMULATION IN ADULTS AND THE ELDERLY WITH REFRACTORY EPILEPSY: A COMPARATIVE ANALYSIS [P05.073]

Sandipan Pati, Richard Zimmerman, Katherine Noe, Joseph Drazkowski, Amy Theiler, Deborah Shulman, Lisa Tapsell, Phoenix, AZ; Joseph Sirven, Scottsdale, AZ

Vagus nerve stimulation (VNS) is a nonpharmacologic option for the management of intractable seizures for patients who are not good candidates for resective epilepsy surgery. In long-term clinical studies of adult patients with intractable epilepsy, VNS has been shown to reduce the seizure rate by approximately 30% to 40%, and to reduce seizure frequency by 50% or more in approximately 40% to 45% of patients.^1,2 In this poster, the authors examined the effectiveness of VNS in older adults with intractable epilepsy. They suggested that VNS may be especially helpful for older patients (60 years old) because it may improve seizure control with fewer antiepileptic drugs (AEDs), resulting in a reduction of the risk of drug interactions and medication-related adverse effects. VNS was shown to improve seizures in a previous 3-month study of patients over the age of 50 with intractable seizures.³ However, few studies have compared the effectiveness of VNS between elderly patients and younger adults, and the long-term efficacy and tolerability of VNS in the elderly are not well known.

Pati et al conducted a retrospective analysis of the long-term efficacy of VNS in adults with refractory epilepsy. The authors examined outcome data for all of the patients who underwent VNS at a single institution between June 1999 and February 2008 and who had been followed for at least 1 year after implantation. The mean age of the patients at baseline was 44 years (range, 16–81). A total of 67 patients underwent VNS implantation, and 55 of the patients were considered eligible for participation in the study. Treatment response, which was defined as a reduction in seizure frequency of at least 50% from baseline, was noted for 25 of the 55 patients (45%) after a mean duration of follow-up of 3.8 years (range, 1.6–8 years). Three patients (5%) were seizure free with VNS and AEDs. VNS implantation was associated with significant improvement in patient-rated quality of life for 32 of the 55 patients (58%). There were no discernable associations between treatment success and specific epilepsy syndromes (eg, temporal lobe, idiopathic generalized epilepsy), magnetic resonance imaging evidence of detectable pathology, or evidence of lateralized lesion pattern on electroencephalography.

In order to evaluate the effectiveness of VNS in older patients, the investigators compared the treatment response rates for patients over the age of 60 (n = 9) with the response rate for patients who were ages 60 years or younger (n = 46). Treatment response was noted for 8 of the 9 older patients (89%) compared with 17 of 46 of the younger patients (36%), a statistically significant difference favoring the older patients (P = .007).

The most common adverse events included hoarseness of voice during stimulation (12 patients; 28%), mood disturbance or irritability (9 patients; 21%), and cough (5 patients; 12%). Balance problems were noted for 4 patients (9%), especially among the elderly subjects. Treatment was discontinued by 3 patients; lack of efficacy or the desire to try another treatment were the most common reasons for discontinuation.

Vagus nerve stimulation appears to provide a persistent long-term reduction in seizure frequency for many patients with intractable epilepsy, with a favorable safety profile. The long-term benefit of VNS may be greater in older patients, although this observation requires replication in future studies. In addition, stimulation parameters should be studied in this population to determine whether side effects can be avoided.

References
1. Scherrmann J, Hoppe C, Kral T, et al. Vagus nerve stimulation: clinical experience in a large patient series. J Clin Neurophysiol. 2001;18:408-414.
2. DeGiorgio CM, Thompson J, Lewis P, et al. Vagus nerve stimulation: analysis of device parameters in 154 patients during the long-term XE5 study. Epilepsia. 2001;42:1017-1020.
3. Sirven JI, Sperling M, Naritoku D, et al. Vagus nerve stimulation therapy for epilepsy in older adults. Neurology. 2000;54:1179-1182.