Abstracts

Rationale: VNS has been an approved add-on therapy for intractable epilepsy since 1997. Nonetheless, few studies have demonstrated long term efficacy. The aim of our study was to assess seizure outcomes for up to 15 years and to evaluate patient satisfaction on VNS therapy. Methods: Following IRB approval, patients who had VNS implantation for intractable epilepsy from 1998 to 2013 were identified. Demographics, age at epilepsy onset and VNS implantation, seizure frequency and number of antiepileptic drugs (AEDs) before and after VNS implantation were collected. Phone surveys were conducted in May 2014 to determine the patients' current seizure frequency and satisfaction rate. Surgical outcomes were based on modified Engel's classification (I: seizure free/rare simple partial seizures; II: >90% seizure reduction (SR), III: 50-90% SR, IV:<50% SR) and McHugh classification (I:80-100% SR; II:50-79% SR, III: <50% SR, IV: Magnet benefits only, V: No improvement). Results: A total of 184 patients underwent VNS implantation, 12 of which were deceased at the time of the phone survey. Of the 172, 64 (37%) were contacted and completed the survey. Of these, 53% were male, with mean age of epilepsy onset 10.1 years (range birth to 58 y). 25 (40%) patients had extra-temporal partial epilepsy, 14 (22%) temporal, 14 (22%) symptomatic generalized, 2 (3%) idiopathic generalized and 8 (13%) multiple epilepsy types. Twenty nine (45%) had development delays, 11 (18%) history of status epilepticus and 21(33%) resective epilepsy surgery before VNS. Median number of seizures per month before VNS was 14 (range: 0.5 to 600). Mean age at VNS implantation was 31 (range 5 to 62 y) with a mean of 19.7 years between epilepsy onset and VNS implantation (range 2 to 46 y). Median number of AEDs before VNS and at the time of survey was unchanged at 3. 8 patients (13%) experienced complications with VNS. Median time between VNS implantation and phone survey was 7 years (range 0 to 15 y), with 36% being more than 10 years. All but 1 of the patients was still receiving VNS therapy and that patient had removal after 2 years. Fifty two patients (81%) said having VNS was worthwhile, 9 (14%) said it was not and 3 (5%) said they were unsure. Of the 60 patients with frequency information, 13 (22%) had a modified Engel classification of I, 12 (20%) of II, 17 (28%) of III and 18 (30%) of IV. Per the McHugh classification, 30 (50%) had class I, 12 (20%) II, 7 (12%) III and 11 (18%) V. Conclusions: Our study demonstrates that VNS is a well-tolerated long term adjunctive therapy for epilepsy leading to 80-100% seizure reduction in 50% patients, and seizure freedom in 22% patients. The great majority of patients (81%) expressed satisfaction with VNS therapy. Additional assessment of psychosocial outcomes is necessary to better establish the overall impact of VNS therapy on the quality of life of patients with intractable epilepsy.