Factors correlated with intracranial interictal epileptiform discharges in refractory epilepsy

Robert J. Quon, Stephen Meisenhelter, Richard H. Adamovich-Zeitlin, Yinchen Song, Sarah A. Steimel, Edward J. Camp, Markus E. Testorf, Todd A. MacKenzie, Robert E. Gross, Bradley C. Lega, Michael R. Sperling, Michael J. Kahana, Barbara C. Jobst

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Objective: This study was undertaken to evaluate the influence that subject-specific factors have on intracranial interictal epileptiform discharge (IED) rates in persons with refractory epilepsy. Methods: One hundred fifty subjects with intracranial electrodes performed multiple sessions of a free recall memory task; this standardized task controlled for subject attention levels. We utilized a dominance analysis to rank the importance of subject-specific factors based on their relative influence on IED rates. Linear mixed-effects models were employed to comprehensively examine factors with highly ranked importance. Results: Antiseizure medication (ASM) status, time of testing, and seizure onset zone (SOZ) location were the highest-ranking factors in terms of their impact on IED rates. The average IED rate of electrodes in SOZs was 34% higher than the average IED rate of electrodes outside of SOZs (non-SOZ; p <.001). However, non-SOZ electrodes had similar IED rates regardless of the subject's SOZ location (p =.99). Subjects on older generation (p <.001) and combined generation (p <.001) ASM regimens had significantly lower IED rates relative to the group taking no ASMs; newer generation ASM regimens demonstrated a nonsignificant association with IED rates (p =.13). Of the ASMs included in this study, the following ASMs were associated with significant reductions in IED rates: levetiracetam (p <.001), carbamazepine (p <.001), lacosamide (p =.03), zonisamide (p =.01), lamotrigine (p =.03), phenytoin (p =.03), and topiramate (p =.01). We observed a nonsignificant association between time of testing and IED rates (morning–afternoon p =.15, morning–evening p =.85, afternoon–evening p =.26). Significance: The current study ranks the relative influence that subject-specific factors have on IED rates and highlights the importance of considering certain factors, such as SOZ location and ASM status, when analyzing IEDs for clinical or research purposes.

Original languageEnglish (US)
Pages (from-to)481-491
Number of pages11
Issue number2
StatePublished - Feb 2021


  • clinical factors
  • demographics
  • epilepsy
  • interictal epileptiform discharges
  • intracranial monitoring

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology


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