title: Latency of interictal epileptiform discharges in long-term EEG recordings in epilepsy patients.
abstract: OBJECTIVE
  To assess the latency of interictal epileptiform discharges (IED) and seizures in long-term EEG recordings of patients with epilepsy.
  
  
  METHODS
  IED latency was measured in 210 consecutive patients (mean (SD) age 38.6 ± 13.9 years) with active epilepsy and the relationship to clinical variables was analyzed retrospectively. Median duration of EEG recording was 101.5h (95% confidence interval [CI] 92 to 117 h).
  
  
  RESULTS
  IEDs were absent in 45 (21.4%) and present in 165 (78.6%) patients who had a longer duration (p < 0.001) and early onset (p < 0.01) of epilepsy and more often had IEDs in prior standard EEGs (p < 0.01), a structural etiology (OR 2.4, CI: 2.1-2.7), or temporal lobe epilepsy (OR 9.6, CI: 9.0-10.2). IED latency did not correlate with other clinical variables. Median latency to the emergence of the first IED was 9.3h (CI: 7.5-11.4) occurring in 7.3%, 9.7%, 74.6%, 87.9%, and 96.4% within 20 min, 30 min, 24h, 48 h, and 72 h, respectively. Seizure frequency was higher in patients with (n = 165) than without IEDs (n = 45) (72.1% vs. 46.6%, p < 0.01) and seizure latency (median 21.6h, CI: 16.8-27.3) was influenced by the presence of IEDs, whereas the presence of seizures did not influence the latency and frequency of IEDs.
  
  
  CONCLUSIONS
  If present, in the majority of epilepsy patients IEDs occurred during the first 72 h of long-term video-EEG recording. Repeated video-EEG or video recordings of habitual seizures are needed to minimize false negative studies.
authors.affiliation: Department of Neurology, University Medical Center of the Johannes Gutenberg-University Mainz, Germany. Electronic address: WerhahnKJ@gmail.com.
authors.forename: Konrad J
authors.initials: KJ
authors.lastname: Werhahn
authors.affiliation: Epilepsy Center, Department of Neurology, University of Munich, Germany. Electronic address: elisabeth.hartl@med.uni-muenchen.de.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Hartl
authors.affiliation: Department of Neurology, University Medical Center of the Johannes Gutenberg-University Mainz, Germany. Electronic address: kristin.hamann@gmail.com.
authors.forename: Kristin
authors.initials: K
authors.lastname: Hamann
authors.affiliation: Department of Neurology, University Medical Center of the Johannes Gutenberg-University Mainz, Germany. Electronic address: breimhor@uni-mainz.de.
authors.forename: Markus
authors.initials: M
authors.lastname: Breimhorst
authors.affiliation: Epilepsy Center, Department of Neurology, University of Munich, Germany. Electronic address: soheyl.noachtar@med.uni-muenchen.de.
authors.forename: Soheyl
authors.initials: S
authors.lastname: Noachtar
mesh_terms: D000328:Adult; D000927:Anticonvulsants / Q000627:therapeutic use; D001921:Brain / Q000187:drug effects / Q000503:physiopathology*; D004569:Electroencephalography / Q000379:methods; D004827:Epilepsy / Q000188:drug therapy / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D012640:Seizures / Q000188:drug therapy / Q000503:physiopathology; D013997:Time Factors; D014741:Video Recording / Q000379:methods
chemical_list: D000927:Anticonvulsants
keywords: Epilepsy; Interictal epileptiform discharges; Latency; Long-term EEG