title: Long term effects on epileptiform activity with vagus nerve stimulation in children.
abstract: OBJECTIVE
  We report long-term effects of vagus nerve stimulation (VNS) on epileptiform activity in 15 children, and how these changes are related to activity stage and to clinical effects on seizure reduction, seizure severity (NHS3) and quality of life (QOL).
  
  
  METHODS
  Initially, and after 3 and 9 months of VNS-treatment, 15 children were investigated with 24 h ambulatory EEG monitoring for spike detection. The number of interictal epileptiform discharges (IEDs) and the inter spike intervals (ISIs) were analysed during 2 h in the awake state, and 1h of rapid eye movement (REM)-, spindle- and delta-sleep, respectively. Total number and duration of electrographic seizure episodes were also analysed.
  
  
  RESULTS
  At 9 months the total number of IEDs was significantly reduced (p=0.04). There was a tendency of reduction in all activity stages, and significantly so in delta-sleep (p=0.008). Total electrographic seizure number was significantly reduced in the 24 h EEG at 3 and 9 months (p=0.03, 0.05). There was a significant concordance in direction of changes in epileptiform activity and electrographic seizures at 9 months (p=0.04). Concordance in direction of changes was seen in 9 of 15 children between clinical seizures and IED (p>0.3), in 10 of 15 children between QOL and IED (p=0.3) and in 8 of 15 children between NHS3 and IED (p>0.3). There was no direct correlation between the extent of improvement in these clinical data and the degree of spike reduction.
  
  
  CONCLUSIONS
  This study shows that VNS reduces IEDs especially in REM and delta sleep, as well as the number of electrographic seizures. It also shows a concordance between reduction in IEDs and electrographic seizures.
authors.affiliation: Department of Paediatrics, University Hospital, SE-221 85 Lund, Sweden. tove.hallbook@skane.se
authors.forename: Tove
authors.initials: T
authors.lastname: Hallböök
authors.forename: Johan
authors.initials: J
authors.lastname: Lundgren
authors.forename: Gösta
authors.initials: G
authors.lastname: Blennow
authors.forename: Lars-Göran
authors.initials: LG
authors.lastname: Strömblad
authors.forename: Ingmar
authors.initials: I
authors.lastname: Rosén
mesh_terms: D000200:Action Potentials / Q000502:physiology / Q000528:radiation effects; D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004599:Electric Stimulation Therapy; D004569:Electroencephalography / Q000379:methods / Q000706:statistics & numerical data*; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology / Q000628:therapy*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D016037:Single-Blind Method; D018709:Statistics, Nonparametric; D013997:Time Factors; D014630:Vagus Nerve / Q000503:physiopathology / Q000528:radiation effects*