title: Increase in 20-50 Hz (gamma frequencies) power spectrum and synchronization after chronic vagal nerve stimulation.
abstract: OBJECTIVE
  Though vagus nerve stimulation (VNS) is an important option in pharmaco-resistant epilepsy, its mechanism of action remains unclear. The observation that VNS desynchronised the EEG activity in animals suggested that this mechanism could be involved in VNS antiepileptic effects in humans. Indeed VNS decreases spiking bursts, whereas its effects on the EEG background remain uncertain. The objective of the present study is to investigate how VNS affects local and inter regional syncronization in different frequencies in pharmaco-resistant partial epilepsy.
  
  
  METHODS
  Digital recordings acquired in 11 epileptic subjects 1 year and 1 week before VNS surgery were compared with that obtained 1 month and 1 year after VNS activation. Power spectrum and synchronization were then analyzed and compared with an epileptic group of 10 patients treated with AEDs only.
  
  
  RESULTS
  VNS decreases the synchronization of theta frequencies (P < 0.01), whereas it increases gamma power spectrum and synchronization (< 0.001 and 0.01, respectively).
  
  
  CONCLUSIONS
  The reduction of theta frequencies and the increase in power spectrum and synchronization of gamma bands can be related to VNS anticonvulsant mechanism. In addition, gamma modulation could also play a seizure-independent role in improving attentional performances.
  
  
  CONCLUSIONS
  These results suggest that some antiepileptic mechanisms affected by VNS can be modulated by or be the reflection of EEG changes.
authors.affiliation: Dipartimento di Scienze Neurologiche e Cardiovascolari, Policlinico Universitario, Università di Cagliari, SS 554, Bivio Sestu, 09042 Monserrato, Italy. marrosu@unica.it
authors.forename: F
authors.initials: F
authors.lastname: Marrosu
authors.forename: F
authors.initials: F
authors.lastname: Santoni
authors.forename: M
authors.initials: M
authors.lastname: Puligheddu
authors.forename: L
authors.initials: L
authors.lastname: Barberini
authors.forename: A
authors.initials: A
authors.lastname: Maleci
authors.forename: F
authors.initials: F
authors.lastname: Ennas
authors.forename: M
authors.initials: M
authors.lastname: Mascia
authors.forename: G
authors.initials: G
authors.lastname: Zanetti
authors.forename: A
authors.initials: A
authors.lastname: Tuveri
authors.forename: G
authors.initials: G
authors.lastname: Biggio
mesh_terms: D000328:Adult; D003344:Cortical Synchronization; D003627:Data Interpretation, Statistical; D004599:Electric Stimulation Therapy; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004827:Epilepsy / Q000503:physiopathology* / Q000628:therapy; D005260:Female; D006801:Humans; D008297:Male; D013686:Telemetry; D014630:Vagus Nerve / Q000502:physiology*