Changes in eeg frequency power spectrum and synchronization in patients affected by partial epilepsy following vagal nerve stimulation

Objective: To determine the effects of vagus nerve stimulation (VNS) on the power spectrum and intra- or interhemispheric synchronization of EEG activity in adults with drug-resistant epilepsy. Methods: The average of the power spectrum profiles recorded 1 year and 1 week before VNS surgery was compared with that obtained 1 year after surgery in eleven adults affected by drug-resistant epilepsy. Similar recordings were obtained from one group of subjects affected by partial epilepsy and treated with AEDs only. Power spectra were computed with fast Fourier transform algorithms, and synchronization was determined by coherence and interdependence statistical analyses. Results: The epileptic patients before surgery showed increased power spectra for all EEG frequencies compared with control groups. VNS induced a further increase in the power spectrum and increased synchronization of gamma frequencies (20 and50 Hz) in the patients, with these effects of VNS being more prominent in the right cortex. In addition, VNS induced decreases in intra- or interhemispheric synchronization of theta frequencies (4 to 7.5 Hz) and, to a lesser extent, of delta (0.5 to 3 Hz), alpha (8 to 12 Hz), and beta (13 to 20 Hz) bands without a significant effect on the corresponding power spectra. The control groups failed to show significant changes over similar time periods. Conclusion: These results show that VNS induces moderate decrease in synchronization of several EEG frequencies, while specifically and markedly increases the power spectrum and synchronization of the gamma band. Given the manifold activities of the vagal stimulation upon several brain areas, these results suggest that the modifications of the power spectrum in the long period can be part of the antiseizure mechanism as well as of other independent effects that remain to be elucidated.

@Article{SM04a,
  author       = {Santoni, F. and Marrosu, F.},
  title        = {Changes in eeg frequency power spectrum and synchronization in patients affected by partial epilepsy following vagal nerve stimulation},
  journal      = {Epilepsia},
  year         = {2004},
  url          = {https://publications.crs4.it/pubdocs/2004/SM04a},
}