title: Widespread inter-ictal excitability changes in patients with temporal lobe epilepsy: A TMS/MEG study.
abstract: OBJECTIVE
  Transcranial magnetic stimulation (TMS) has been used to elucidate the altered balance between excitatory and inhibitory circuits in the motor cortex in epilepsy; however, TMS could not well assess excitability changes beyond the motor cortex. This study aimed to address the spatial profile of cortical excitability changes in patients with temporal lobe epilepsy (TLE) by using TMS and magnetoencephalography (MEG).
  
  
  METHODS
  Eighteen patients with TLE and 18 healthy control subjects were recruited. Resting motor threshold (RMT) and intracortical inhibition (ICI) were measured to reflect motor cortical excitability by using TMS. A whole-head MEG was applied to record auditory and somatosensory evoked responses to paired-pulse stimuli. A paired-pulse inhibition (PPI) ratio, defined as the amplitude ratio between responses to the second and the first stimuli, was used to assess the auditory and somatosensory cortical excitability. A high PPI ratio suggests an increase in cortical excitability, while a low ratio indicates a decrease in excitability.
  
  
  RESULTS
  Compared to control subjects, TLE patients exhibited increased RMT in motor cortex and higher PPI ratios for auditory P50m and somatosensory P35m responses. Notably, patients with a lower seizure frequency tended to exhibit a higher RMT or a lower P35m PPI ratio.
  
  
  CONCLUSIONS
  Present data suggest that the cortical excitability alteration in focal epilepsy is widely distributed beyond the epileptic focus and the profiles of excitability change correlate with clinical severity in terms of seizure frequency. Combined MEG and TMS studies provide new insight into the inter-ictal cortical excitability profiles in patients with epilepsy.
authors.affiliation: Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan; Laboratory of Neurophysiology, Taipei Veterans General Hospital, Taipei, Taiwan; Integrated Brain Research Laboratory, Taipei Veterans General Hospital, Taipei, Taiwan. Electronic address: j03m61@gmail.com.
authors.forename: Wan-Yu
authors.initials: WY
authors.lastname: Hsu
authors.affiliation: Institute of Physiology, National Yang-Ming University, Taipei, Taiwan. Electronic address: ejiu4z@gmail.com.
authors.forename: Yi-Feng
authors.initials: YF
authors.lastname: Kuo
authors.affiliation: Department of Neurology, National Yang-Ming University, Taipei, Taiwan; Department of Neurology, Taipei Veterans General Hospital, Taipei, Taiwan. Electronic address: kkliao@vghtpe.gov.tw.
authors.forename: Kwong-Kum
authors.initials: KK
authors.lastname: Liao
authors.affiliation: Department of Neurology, National Yang-Ming University, Taipei, Taiwan; Department of Neurology, Taipei Veterans General Hospital, Taipei, Taiwan. Electronic address: alicehyyu@gmail.com.
authors.forename: Hsiang-Yu
authors.initials: HY
authors.lastname: Yu
authors.affiliation: Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan; Department of Neurology, National Yang-Ming University, Taipei, Taiwan; Institute of Physiology, National Yang-Ming University, Taipei, Taiwan; Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan; Laboratory of Neurophysiology, Taipei Veterans General Hospital, Taipei, Taiwan; Integrated Brain Research Laboratory, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Neurology, Taipei Veterans General Hospital, Taipei, Taiwan. Electronic address: yylin@vghtpe.gov.tw.
authors.forename: Yung-Yang
authors.initials: YY
authors.lastname: Lin
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology*; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology*; D005072:Evoked Potentials, Auditory; D019054:Evoked Potentials, Motor / Q000502:physiology; D005073:Evoked Potentials, Somatosensory; D005260:Female; D007839:Functional Laterality; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D010812:Physical Stimulation; D012640:Seizures; D012720:Severity of Illness Index; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: Cortical excitability; Magnetoencephalography (MEG); Paired-pulse inhibition (PPI); Temporal lobe epilepsy (TLE); Transcranial magnetic stimulation (TMS)