title: Spikes on the postoperative EEG are related to preoperative spike frequency and postoperative seizures.
abstract: OBJECTIVE
  To investigate the factors which influence the persistence of interictal epileptiform discharges (IED) after epilepsy surgery.
  
  
  METHODS
  In this retrospective study we included patients with intractable medial temporal lobe epilepsy (MTLE) who underwent presurgical evaluation including high-resolution MRI and video-EEG monitoring with seizure registration prior to an anterior temporal lobe resection. The postsurgical outcome was assessed by our team 6 months and 2 years after the surgery.
  
  
  RESULTS
  One hundred and forty-seven patients fulfilled the inclusion criteria. The mean age of the patients was 31.8 (range 16-59 years). In 22 patients (15%) interictal epileptiform discharges were present on the postoperative routine EEG. We found that both the preoperative spike frequency ( P < 0.001 ) and postoperative seizures ( P = 0.04 ) were independently associated with the presence of IED on the postoperative routine EEG. The preoperative spike frequency was not associated with the postoperative outcome. The extent of resection showed no influence on the presence of postoperative IED.
  
  
  CONCLUSIONS
  We hypothesize that two factors independently influence the presence of postoperative spikes: chronic interictal disturbance (represented as preoperative spike frequency) and the acute (postoperative) seizures. Our study confirmed that persistent postoperative IED had a prognostic value regarding the outcome of the epilepsy surgery.
authors.affiliation: Epilepsie-Zentrum Bethel, Mara Krankenhaus, Maraweg 21, Bielefeld 33617, Germany. janszky@index.hu
authors.forename: J
authors.initials: J
authors.lastname: Janszky
authors.forename: R
authors.initials: R
authors.lastname: Schulz
authors.forename: M
authors.initials: M
authors.lastname: Hoppe
authors.forename: A
authors.initials: A
authors.lastname: Ebner
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D004569:Electroencephalography / Q000379:methods / Q000706:statistics & numerical data*; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000503:physiopathology*; D011300:Preoperative Care / Q000379:methods / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D018709:Statistics, Nonparametric