title: Refractory epilepsy in tuberous sclerosis: vagus nerve stimulation with or without subsequent resective surgery.
abstract: OBJECTIVE
  The goal of the work described here was to assess the efficacy and safety of vagus nerve stimulation in a cohort of patients with tuberous sclerosis complex with refractory epilepsy. Furthermore, we examined the impact of vagus nerve stimulation failure on the ultimate outcome following subsequent intracranial epilepsy surgery.
  
  
  METHODS
  A retrospective review was performed on 19 patients with refractory epilepsy and TSC who underwent vagus nerve stimulator (VNS) implantation. There were 11 (58%) females and 8 (42%) males aged 2 to 44 years when the VNS was implanted (mean: 14.7+/-12 years). Twelve patients underwent primary VNS implantation after having failed a mean of 7.1 antiepileptic drugs. Two patients (17%) had generalized epilepsy, one had a single seizure focus, three (25%) had multifocal epilepsy, and six (50%) had multifocal and generalized epilepsy. Seven patients were referred for device removal and evaluation for intracranial procedures. One patient in the primary implantation group was lost to follow-up and excluded from outcome analysis.
  
  
  RESULTS
  All implantations and removals were performed without permanent complications. The duration of treatment for primary VNS implants varied from 8.5 months to 9.6 years (mean: 4.9 years). Mean seizure frequency significantly improved following VNS implantation (mean reduction: 72%, P<0.002). Two patients had Engel Class I (18%), one had Class II (9%), seven had Class III (64%), and one had Class IV (9%) outcome. Three patients with poor response to vagus nerve stimulation therapy at our center underwent resection of one or more seizure foci (Engel Class I, two patients; Engel Class III, one patient). Seven patients referred to our center for VNS removal and craniotomy underwent seizure focus resection (6) or corpus callosotomy (1) (Engel Class II: 2, Engel III: 2; Engel IV: 3). In total, 8 of 10 (80%) patients experienced improved seizure control following intracranial surgery (mean reduction: 65%, range: 0-100%, P<0.05).
  
  
  CONCLUSIONS
  VNS is a safe and effective treatment option for medically refractory epilepsy in patients with tuberous sclerosis complex. Nine of 11 patients (82%) experienced at least a 67% reduction in seizure burden. Lack of response to vagus nerve stimulation does not preclude subsequent improvement in seizure burden with intracranial epilepsy surgery.
authors.affiliation: Department of Neurosurgery, New York University Langone Medical Center, New York, NY 10016, USA. robert.elliott@nyumc.org
authors.forename: Robert E
authors.initials: RE
authors.lastname: Elliott
authors.forename: Chad
authors.initials: C
authors.lastname: Carlson
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Kalhorn
authors.forename: Yaron A
authors.initials: YA
authors.lastname: Moshel
authors.forename: Howard L
authors.initials: HL
authors.lastname: Weiner
authors.forename: Orrin
authors.initials: O
authors.lastname: Devinsky
authors.forename: Werner K
authors.initials: WK
authors.lastname: Doyle
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography; D004827:Epilepsy / Q000209:etiology* / Q000628:therapy*; D005260:Female; D006801:Humans; D008297:Male; D009493:Neurosurgery / Q000379:methods*; D017063:Outcome Assessment, Health Care; D012189:Retrospective Studies; D014402:Tuberous Sclerosis / Q000150:complications* / Q000628:therapy*; D055536:Vagus Nerve Stimulation / Q000379:methods*; D055815:Young Adult