Factors correlated with intracranial interictal epileptiform discharges in refractory epilepsy

Epilepsia. 2021 Feb;62(2):481-491. doi: 10.1111/epi.16792. Epub 2020 Dec 17.

Abstract

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.

Keywords: clinical factors; demographics; epilepsy; interictal epileptiform discharges; intracranial monitoring.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adult
  • Anticonvulsants / therapeutic use*
  • Attention
  • Carbamazepine / therapeutic use
  • Drug Resistant Epilepsy / drug therapy
  • Drug Resistant Epilepsy / physiopathology*
  • Electrocorticography
  • Female
  • Humans
  • Lacosamide / therapeutic use
  • Lamotrigine / therapeutic use
  • Levetiracetam / therapeutic use
  • Male
  • Mental Recall
  • Middle Aged
  • Phenytoin / therapeutic use
  • Time Factors
  • Topiramate / therapeutic use
  • Zonisamide / therapeutic use

Substances

  • Anticonvulsants
  • Topiramate
  • Carbamazepine
  • Levetiracetam
  • Zonisamide
  • Lacosamide
  • Phenytoin
  • Lamotrigine