title: Single pulse electrical stimulation for identification of structural abnormalities and prediction of seizure outcome after epilepsy surgery: a prospective study.
abstract: BACKGROUND
  Abnormal late responses to single pulse electrical stimulation (SPES) in patients with intracranial recordings can identify epileptogenic cortex. We aimed to investigate the presence of neuropathological abnormalities in abnormal SPES areas and to establish if removal of these areas improved postsurgical seizure control.
  
  
  METHODS
  We studied abnormal responses to SPES during chronic intracranial recordings in 40 consecutive patients who were thereafter operated on because of refractory epilepsy and had a follow-up period of at least 12 months.
  
  
  RESULTS
  22 patients had abnormal responses to SPES exclusively located in resected regions (96% with favourable outcome), seven had abnormal responses to SPES located in resected and non-resected regions (71% with favourable outcome), three had abnormal responses to SPES exclusively outside the resected region (none with favourable outcome), and eight did not have abnormal responses to SPES (62.5% with favourable outcome). Surgical outcome was significantly better when areas with abnormal responses to SPES were completely resected compared with partial or no removal of abnormal SPES areas (p=0.006). Neuropathological examination showed structural abnormalities in the abnormal SPES areas in 26 of the 29 patients in whom these regions were resected, despite the absence of clear MRI abnormalities in nine patients.
  
  
  CONCLUSIONS
  Abnormal responses to SPES are functional markers of epileptogenic structural abnormalities, and can identify epileptogenic cortex and predict surgical outcome, especially when a frontal or temporal focus is suspected.
authors.affiliation: Department of Clinical Neurophysiology, Guy's, King's and St Thomas' School of Medicine, London, UK.
authors.forename: Antonio
authors.initials: A
authors.lastname: Valentín
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Alarcón
authors.forename: Mrinalini
authors.initials: M
authors.lastname: Honavar
authors.forename: Jorge J
authors.initials: JJ
authors.lastname: García Seoane
authors.forename: Richard P
authors.initials: RP
authors.lastname: Selway
authors.forename: Charles E
authors.initials: CE
authors.lastname: Polkey
authors.forename: Colin D
authors.initials: CD
authors.lastname: Binnie
mesh_terms: D000293:Adolescent; D000328:Adult; D001932:Brain Neoplasms / Q000150:complications / Q000601:surgery; D002540:Cerebral Cortex / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004568:Electrodiagnosis; D004569:Electroencephalography; D005260:Female; D005625:Frontal Lobe / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D019635:Neurosurgical Procedures; D011446:Prospective Studies; D012640:Seizures / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery*; D013702:Temporal Lobe / Q000601:surgery; D016896:Treatment Outcome