title: Effects of two different cycles of vagus nerve stimulation on interictal epileptiform discharges.
abstract: OBJECTIVE
  To evaluate the effects of two cycles of vagus nerve stimulation (VNS), 30 s/5 min and 7 s/18 s on the interictal epileptiform discharges (IEDs).
  
  
  METHODS
  Twenty patients were studied, 12 with generalized and 8 with partial seizures. An EEG of 120 channels was performed during 3 different conditions, each one lasting 30 min: basal state (BS), 30 s/5 min and 7 s/18 s VNS cycles. The number and duration of IEDs, time of IEDs in 1 min (TIEDM), IEDs/NIEDs index and the spike-free period (SFP) were determined.
  
  
  RESULTS
  In 16 patients (80%), IED decreased during 30 s/5 min cycle (Group 1) and increased in 4 (Group 2). In Group 1, during the 30 s/5 min cycle the following variables showed a decrease: TIEDM, from 12.64 s to 9.62 s (p=0.001); IED/NIED index, from 0.53 to 0.31 (p=0.021), and IED duration, from 1.57 s to 1.05 s (p=0.015); whereas SFP duration increased from 20.06 s to 37.73 s (p=0.008). The decrease in IED was 41% and the increase in SFP 88%. In the 7s/18s cycle, only SFP had an increase, 72% (p<0.043). In Group 2, an increase in IED during both cycles was found. In the 30 s/5 min cycle, TIEDM increased 56% (p=0.042) and IED/NIED index 259% (p=0.040).
  
  
  CONCLUSIONS
  VNS modifies IED in an acute form, in 80% of patients the 30 s/5 min cycle decreases the epileptiform activity and it is not modified by 7 s/18 s cycle. In 20% of patients, both cycles increase the epileptiform activity.
authors.affiliation: Instituto de Neurobiología, Campus UNAM-UAQ Juriquilla, Querétaro, Qro. 76230, México. santiago@inb.unam.mx
authors.forename: Efraín
authors.initials: E
authors.lastname: Santiago-Rodríguez
authors.forename: Mario
authors.initials: M
authors.lastname: Alonso-Vanegas
authors.forename: Lizbeth
authors.initials: L
authors.lastname: Cárdenas-Morales
authors.forename: Thalía
authors.initials: T
authors.lastname: Harmony
authors.forename: Mario
authors.initials: M
authors.lastname: Bernardino
authors.forename: Antonio
authors.initials: A
authors.lastname: Fernández-Bouzas
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004558:Electric Stimulation / Q000379:methods*; D004569:Electroencephalography; D004827:Epilepsy / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012640:Seizures / Q000503:physiopathology*; D014630:Vagus Nerve / Q000502:physiology*