title: Cortical excitability varies upon ictal onset patterns in neocortical epilepsy: a cortico-cortical evoked potential study.
abstract: OBJECTIVE
  To better understand pathological neuronal excitation in epilepsy by comparing cortico-cortical evoked potential (CCEP) responses in regions with different ictal onset patterns: focal paroxysmal fast (PF) and repetitive spiking (RS).
  
  
  METHODS
  Fourteen patients undergoing invasive monitoring (six patients with PF and eight with RS) were studied with CCEPs. A repetitive 1 Hz bipolar electrical stimulus was applied to both the ictal onset region (iCCEP) and to a control region (nCCEP) and CCEPs were recorded from the surrounding electrodes. The two groups were compared by subtracting the amplitude of nCCEP from that of iCCEP (CCEP(ictal-control)) at each stimulus intensity, and then normalizing the amplitudes of iCCEP at maximum stimulus intensity by dividing by nCCEP (CCEP(ictal/control)).
  
  
  RESULTS
  The CCEP response to stimulation in the ictal onset region was significantly larger than to control stimulation for both ictal patterns (paroxysmal fast: P=0.02, repetitive spiking: P<0.01), with repetitive spiking group amplitudes higher than the paroxysmal fast group (CCEP(ictal-control): P<0.01 and CCEP(ictal/control): P=0.04).
  
  
  CONCLUSIONS
  Pro-epileptic excitability is more accentuated in regions showing an ictal repetitive spiking pattern than a paroxysmal fast pattern.
  
  
  CONCLUSIONS
  These findings confirm in a new way that cortical excitability varies depending on the ictal onset pattern.
authors.affiliation: Epilepsy Center, Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
authors.forename: Rei
authors.initials: R
authors.lastname: Enatsu
authors.forename: Zhe
authors.initials: Z
authors.lastname: Piao
authors.forename: Timothy
authors.initials: T
authors.lastname: O'Connor
authors.forename: Karl
authors.initials: K
authors.lastname: Horning
authors.forename: John
authors.initials: J
authors.lastname: Mosher
authors.forename: Richard
authors.initials: R
authors.lastname: Burgess
authors.forename: William
authors.initials: W
authors.lastname: Bingaman
authors.forename: Dileep
authors.initials: D
authors.lastname: Nair
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D002648:Child; D004558:Electric Stimulation / Q000379:methods; D004569:Electroencephalography / Q000379:methods; D004827:Epilepsy / Q000175:diagnosis / Q000503:physiopathology*; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019579:Neocortex / Q000503:physiopathology*; D055815:Young Adult