title: Vagus nerve stimulation: outcome and predictors of seizure freedom in long-term follow-up.
abstract: OBJECTIVE
  To present long-term outcome and to identify predictors of seizure freedom after vagus nerve stimulation (VNS).
  
  
  METHODS
  All patients who had undergone VNS implantation in the Epilepsy Centre Bethel were retrospectively reviewed. There were 144 patients who had undergone complete presurgical evaluation, including detailed clinical history, magnetic resonance imaging, and long-term video-EEG with ictal and interictal recordings. After implantation, all patients were examined at regular intervals of 4 weeks for 6-9 months. During this period the antiepileptic medication remained constant. All patients included in this study were followed up for a minimum of 2 years.
  
  
  RESULTS
  Ten patients remained seizure-free for more than 1 year after VNS implantation (6.9%). Seizures improved in 89 patients (61.8%) but no changes were observed in 45 patients (31.3%). The following factors were significant in the univariate analysis: age at implantation, multifocal interictal epileptiform discharges, unilateral interictal epileptiform discharge, cortical dysgenesis, and psychomotor seizure. Stepwise multivariate analysis showed that unilateral interictal epileptiform discharges (IEDs), P=0.014, HR=0.112 (95% CIs, 0.019-0.642), cortical dysgenesis P=0.007, HR=0.065 (95% CIs, 0.009-0.481) and younger age at implantation P=0.026, HR=7.533 (95% CIs 1.28-44.50) were independent predictors of seizure freedom in the long-term follow-up.
  
  
  CONCLUSIONS
  VNS implantation may render patients with some forms of cortical dysgenesis (parietooccipital polymicrogyria, macrogyria) seizure-free. Patients with unilateral IEDs and earlier implantation achieved the most benefit from VNS.
authors.affiliation: Department of Neurosurgery, Birjand University of Medical Science, Iran. kazemghaemi@yahoo.com
authors.forename: Kazem
authors.initials: K
authors.lastname: Ghaemi
authors.forename: Alaa Eldin
authors.initials: AE
authors.lastname: Elsharkawy
authors.forename: Reinhard
authors.initials: R
authors.lastname: Schulz
authors.forename: Matthias
authors.initials: M
authors.lastname: Hoppe
authors.forename: Tilman
authors.initials: T
authors.lastname: Polster
authors.forename: Heinz
authors.initials: H
authors.lastname: Pannek
authors.forename: Alois
authors.initials: A
authors.lastname: Ebner
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000704:Analysis of Variance; D000927:Anticonvulsants / Q000627:therapeutic use; D002540:Cerebral Cortex / Q000002:abnormalities; D002648:Child; D002675:Child, Preschool; D004351:Drug Resistance; D004599:Electric Stimulation Therapy / Q000009:adverse effects; D004569:Electroencephalography; D004827:Epilepsy / Q000209:etiology / Q000628:therapy*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008134:Long-Term Care; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012640:Seizures / Q000517:prevention & control*; D016896:Treatment Outcome; D014630:Vagus Nerve / Q000502:physiology*; D055815:Young Adult
chemical_list: D000927:Anticonvulsants