title: Generator replacement in epilepsy patients treated with vagus nerve stimulation.
abstract: OBJECTIVE
  In epilepsy patients treated with vagus nerve stimulation (VNS), the occurrence of end of battery life (EOBL), when the generator will no longer deliver any stimulation, was investigated with regard to seizure control. EOBL is preceeded by end of effective stimulation (EOES) when irregular stimulation may occur.
  
  
  METHODS
  In 14/78 patients, treated with VNS at Ghent University Hospital, generators were replaced at different times following EOES or EOBL. We retrospectively analysed the time of occurrence of EOES and EOBL and seizure control before and after generator replacement.
  
  
  RESULTS
  EOES or EOBL was indicated by loss of seizure control, decreased perception of stimulation and recurrence of depression in 3, 3 and 1/14 patient(s), respectively. In 2 and 1/14 patient(s), EOBL and premature generator failure, respectively, were detected during routine check-up at the epilepsy clinic. In 4/14 patients, generator replacement was performed before estimated EOES. Pre-replacement seizure control could not be regained in 2/14 patients in whom replacement had been postponed for several months. Estimation of EOES and EOBL occurrence proved difficult in individual patients.
  
  
  CONCLUSIONS
  EOES or EOBL may be indicated by loss of seizure control, decreased or irregular perception of stimulation by the patient and loss of other VNS-induced effects. Postponing generator replacement may result into permanent loss of seizure control. In responders we suggest generator replacement before EOBL. Our results call for performance of prospective studies in larger patient groups that may eventually lead to general guidelines on the indication and timing of generator replacement.
authors.affiliation: Reference Center for Refractory Epilepsy, Department of Neurology, Ghent University Hospital, Belgium. kristl.vonck@ugent.be
authors.forename: Kristl
authors.initials: K
authors.lastname: Vonck
authors.forename: Stefanie
authors.initials: S
authors.lastname: Dedeurwaerdere
authors.forename: Liesbeth
authors.initials: L
authors.lastname: De Groote
authors.forename: Vijay
authors.initials: V
authors.lastname: Thadani
authors.forename: Pieter
authors.initials: P
authors.lastname: Claeys
authors.forename: Fleur
authors.initials: F
authors.lastname: Gossiaux
authors.forename: Dirk
authors.initials: D
authors.lastname: Van Roost
authors.forename: Paul
authors.initials: P
authors.lastname: Boon
mesh_terms: D000328:Adult; D000927:Anticonvulsants / Q000493:pharmacokinetics / Q000627:therapeutic use; D002648:Child; D003863:Depression / Q000175:diagnosis / Q000209:etiology; D004351:Drug Resistance; D004553:Electric Conductivity; D004599:Electric Stimulation Therapy / Q000295:instrumentation*; D004827:Epilepsy / Q000188:drug therapy / Q000523:psychology / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D019635:Neurosurgical Procedures / Q000379:methods; D012008:Recurrence; D014159:Transducers; D014630:Vagus Nerve / Q000502:physiology*
chemical_list: D000927:Anticonvulsants