title: Quantitative spectral analysis of vigilance EEG in patients with obstructive sleep apnoea syndrome: EEG mapping in OSAS patients.
abstract: BACKGROUND
  Sleep disruption and blood gas abnormalities, observed in patients with obstructive sleep apnoea (OSA) syndrome, prevent sleep-related restorative processes and induce chemical or structural central nervous system cellular injury. The aim of the study was to determine electroencephalogram (EEG) alterations related to the severity of OSA in patients with OSAS and the effect of the nasal continuous positive air pressure (nCPAP) treatment.
  
  
  METHODS
  Polysomnography and vigilant EEGs were performed in subjects with possible OSA. The mean relative power was calculated for delta, theta, alpha and beta frequency bands. Thirty subjects without and 131 with OSA participated in this study. In 29 male patients with severe OSA, quantitative EEGs were re-evaluated after 6 months of CPAP treatment.
  
  
  RESULTS
  Compared to subjects without OSA, patients with severe OSA showed an increase in relative theta and delta power (occipital, temporal and parietal areas). Six months of nCPAP treatment improved daytime sleepiness of OSA patients. EEG demonstrated a decrease in alpha (frontal, central and temporal areas) and theta (frontal areas) relative power. However, beta relative power was increased mainly in central, and delta relative power, in all brain areas.
  
  
  CONCLUSIONS
  In conclusion, EEG slowing was observed in OSA patients. CPAP treatment improved daytime sleepiness of OSA patients in contrast to the alterations in alpha (decreased) and delta (increased) relative power suggesting a possible persistent brain dysfunction.
authors.affiliation: Department of Psychiatry, School of Medicine, University of Thessaly, University Hospital of Larissa, GR-411 10, Larissa, Greece. axiro@med.uth.gr
authors.forename: Athanasios G
authors.initials: AG
authors.lastname: Xiromeritis
authors.forename: Apostolia A
authors.initials: AA
authors.lastname: Hatziefthimiou
authors.forename: Georgios M
authors.initials: GM
authors.lastname: Hadjigeorgiou
authors.forename: Konstantinos I
authors.initials: KI
authors.lastname: Gourgoulianis
authors.forename: Dimitra N
authors.initials: DN
authors.lastname: Anagnostopoulou
authors.forename: Nikiforos V
authors.initials: NV
authors.lastname: Angelopoulos
mesh_terms: D000328:Adult; D000368:Aged; D001931:Brain Mapping; D058256:Brain Waves / Q000502:physiology*; D002540:Cerebral Cortex / Q000503:physiopathology*; D045422:Continuous Positive Airway Pressure; D006970:Disorders of Excessive Somnolence / Q000503:physiopathology / Q000628:therapy; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D005583:Fourier Analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D012815:Signal Processing, Computer-Assisted; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology* / Q000628:therapy; D055815:Young Adult