title: Can single pulse electrical stimulation provoke responses similar to spontaneous interictal epileptiform discharges?
abstract: OBJECTIVE
  To estimate the proportion of patients where EEG responses to single pulse electrical stimulation (SPES) are similar to spontaneous interictal epileptiform discharges (IEDs) in the same patient, and whether such resemblance is related to seizure onset.
  
  
  METHODS
  We have visually compared the morphology, topography and distribution of IEDs and of SPES responses in 36 patients with intracranial EEG recordings during presurgical evaluation.
  
  
  RESULTS
  Each patient showed between 3 and 17 different IED patterns, located at seizure onset zone and elsewhere. Only 13 patients showed the highest incidence and amplitude of IEDs at the site of focal seizure onset. Twenty-eight patients showed early responses which were similar to at least one IED pattern. Thirty patients showed delayed responses which were always similar to at least one IED pattern and were always located at seizure onset or in its vicinity.
  
  
  CONCLUSIONS
  Early SPES responses often, and delayed responses always, were similar to at least one IED pattern in the same patient. The IEDs resembling delayed responses were those associated with seizure onset.
  
  
  CONCLUSIONS
  The similarities between IEDs and SPES responses suggest that SPES can trigger the mechanisms responsible for generating IEDs, which may become a tool to study the pathophysiology of IEDs.
authors.affiliation: Department of Clinical Neuroscience, Institute of Psychiatry, King's College London, UK; Fortis Malar Hospital, Chennai, India.
authors.forename: Dinesh
authors.initials: D
authors.lastname: Nayak
authors.affiliation: Department of Clinical Neuroscience, Institute of Psychiatry, King's College London, UK; Department of Clinical Neurophysiology, King's College Hospital, London, UK.
authors.forename: Antonio
authors.initials: A
authors.lastname: Valentín
authors.affiliation: Department of Neurosurgery, King's College Hospital, London, UK.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Selway
authors.affiliation: Department of Clinical Neuroscience, Institute of Psychiatry, King's College London, UK; Department of Clinical Neurophysiology, King's College Hospital, London, UK; Departamento de Fisiología, Facultad de Medicina, Universidad Complutense, Madrid, Spain. Electronic address: gonzalo.alarcon@kcl.ac.uk.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Alarcón
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D004558:Electric Stimulation; D004566:Electrodes / Q000145:classification; D004569:Electroencephalography; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D012640:Seizures / Q000175:diagnosis / Q000503:physiopathology*; D055815:Young Adult
keywords: Epilepsy surgery; SPES – interictal epileptiform discharge; Seizure onset; Single pulse electrical stimulation