title: Lateralizing Cortical Excitability in Drug Naïve Patients with Generalized or Focal Epilepsy.
abstract: OBJECTIVE
  Numerous transcranial magnetic stimulation (TMS) studies have defined the characteristic features of TMS in epilepsy. TME parameters were expected to classify the epilepsy syndrome or drug responses. However, the results such as cortical silent periods (CSP) are variable according to conditions of patients. Here, we investigate whether specific TMS parameters have localizing or lateralizing values in drug-naïve epilepsy patients.
  
  
  METHODS
  We recruited 148 consecutive untreated patients with epilepsy (idiopathic generalized epilepsy (IGE) 38, focal epilepsy (FE) 110, mean age 31.4 years) and 38 age- and gender-matched normal subjects. We obtained resting motor threshold (RMT), motor-evoked potential (MEP), CSP, short interval intracortical inhibition (SICI, inter-stimuli interval 2-5 ms), and intracortical facilitation (ICF, inter-stimuli interval 10-20 ms). TMS were performed during a seizure-free state of more than 48 h.
  
  
  RESULTS
  In IGE, no interhemispheric difference in CSP was found (p > 0.05). However, the mean CSP was longer in IGE patients than in normal controls at all stimulus intensities (p < 0.05). The mean CSP in ipsilateral hemisphere (IH) of FE was significantly longer at all stimulus intensities than that in normal controls (p < 0.001). The CSP in IH was longer than that in the contralateral hemisphere of FE. There was no significant difference in CSP between FE and IGE. SICI was significantly reduced only in the IH of FE versus normal subjects. RMT, MEP amplitudes, and ICF did not differ among IGE, FE, and normal controls.
  
  
  CONCLUSIONS
  We found that prolonged CSP and reduced SICI in FE indicate asymmetrically increased cortical inhibition and excitation in the epileptic hemispheres. It suggests that CSP among TMS parameters has a crucial role to lateralize the epileptic hemisphere in FE.
authors.affiliation: Department of Neurology, Neuroscience Center, Samsung Medical Center, Sungkyunkwan University School of Medicine and Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul; Korea; Department of Neurology, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Korea.
authors.forename: Jung Hwa
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Neurology, Neuroscience Center, Samsung Medical Center, Sungkyunkwan University School of Medicine and Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul; Korea.
authors.forename: Eun Yeon
authors.initials: EY
authors.lastname: Joo
authors.affiliation: Department of Neurology, Neuroscience Center, Samsung Medical Center, Sungkyunkwan University School of Medicine and Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul; Korea.
authors.forename: Dae Won
authors.initials: DW
authors.lastname: Seo
authors.affiliation: Department of Neurology, Neuroscience Center, Samsung Medical Center, Sungkyunkwan University School of Medicine and Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul; Korea.
authors.forename: Seung Bong
authors.initials: SB
authors.lastname: Hong
keywords: Cortical silent period; Epilepsy; Intracortical inhibition; Transcranial magnetic stimulation
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