title: An interictal EEG spectral metric for temporal lobe epilepsy lateralization.
abstract: OBJECTIVE
  Visually-obvious abnormalities in the resting baseline EEG--slowing, spiking and high-frequency oscillations (HFOs)--are cardinal, though incompletely understood, features of the seizure onset zone in focal epilepsy. We hypothesized that evidence of cortical network dysfunction in temporal lobe epilepsy (TLE) would persist in the absence of visually-classifiable abnormalities in the baseline EEG recorded within the conventional passband, and that metrics of such dysfunction could serve as a lateralizing diagnostic in TLE.
  
  
  METHODS
  Epochs of resting EEG without significant abnormalities in light sleep over several days were compared between a group of 10 patients with proven TLE and 10 subjects without epilepsy. A novel laterality metric computed from the line length of normalized power spectra from the temporal channels was compared between the two groups.
  
  
  RESULTS
  Significant group differences in spectral line length laterality metric were found between the TLE and control group. At the individual level, seven of 10 TLE patients had highly significant laterality metrics, all concordant with the known laterality of their disease.
  
  
  CONCLUSIONS
  Detailed spectral analysis offers novel insight into TLE network behavior, independent of the orthodox abnormalities of EEG slowing, spikes or HFOs. The results may be deployed in a practical diagnostic manner, offer insight into the EEG manifestations of disordered cellular network architecture in TLE, and maybe understood through simple analogy with the theory of linear time-invariant physical systems.
authors.affiliation: Department of Neurology, University of Texas Health Science Center, Houston, TX, USA. Electronic address: Giridhar.P.Kalamangalam@uth.tmc.edu.
authors.forename: Giridhar P
authors.initials: GP
authors.lastname: Kalamangalam
authors.affiliation: Department of Neurology, University of Texas Health Science Center, Houston, TX, USA.
authors.forename: Lukas
authors.initials: L
authors.lastname: Cara
authors.affiliation: Department of Neurosurgery, University of Texas Health Science Center, Houston, TX, USA.
authors.forename: Nitin
authors.initials: N
authors.lastname: Tandon
authors.affiliation: Department of Neurology, University of Texas Health Science Center, Houston, TX, USA.
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Slater
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D004569:Electroencephalography / Q000379:methods*; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D012146:Rest; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D012890:Sleep; D055815:Young Adult
keywords: Epilepsy surgery; Partial epilepsy; Synchronization