Optimising EEG-fMRI for Localisation of Focal Epilepsy in Children

PLoS One. 2016 Feb 12;11(2):e0149048. doi: 10.1371/journal.pone.0149048. eCollection 2016.

Abstract

Background: Early surgical intervention in children with drug resistant epilepsy has benefits but requires using tolerable and minimally invasive tests. EEG-fMRI studies have demonstrated good sensitivity for the localization of epileptic focus but a poor yield although the reasons for this have not been systematically addressed. While adults EEG-fMRI studies are performed in the "resting state"; children are commonly sedated however, this has associated risks and potential confounds. In this study, we assessed the impact of the following factors on the tolerability and results of EEG-fMRI in children: viewing a movie inside the scanner; movement; occurrence of interictal epileptiform discharges (IED); scan duration and design efficiency. This work's motivation is to optimize EEG-fMRI parameters to make this test widely available to paediatric population.

Methods: Forty-six children with focal epilepsy and 20 controls (6-18) underwent EEG-fMRI. For two 10 minutes sessions subjects were told to lie still with eyes closed, as it is classically performed in adult studies ("rest sessions"), for another two sessions, subjects watched a child friendly stimulation i.e. movie ("movie sessions"). IED were mapped with EEG-fMRI for each session and across sessions. The resulting maps were classified as concordant/discordant with the presumed epileptogenic focus for each subject.

Findings: Movement increased with scan duration, but the movie reduced movement by ~40% when played within the first 20 minutes. There was no effect of movie on the occurrence of IED, nor in the concordance of the test. Ability of EEG-fMRI to map the epileptogenic region was similar for the 20 and 40 minute scan durations. Design efficiency was predictive of concordance.

Conclusions: A child friendly natural stimulus improves the tolerability of EEG-fMRI and reduces in-scanner movement without having an effect on IED occurrence and quality of EEG-fMRI maps. This allowed us to scan children as young as 6 and obtain localising information without sedation. Our data suggest that ~20 minutes is the optimal length of scanning for EEG-fMRI studies in children with frequent IED. The efficiency of the fMRI design derived from spontaneous IED generation is an important factor for producing concordant results.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Attention
  • Brain Mapping / methods
  • Case-Control Studies
  • Child
  • Electroencephalography
  • Epilepsies, Partial / diagnosis*
  • Epilepsies, Partial / physiopathology
  • Female
  • Humans
  • Immobilization
  • Magnetic Resonance Imaging
  • Male
  • Movement
  • Photic Stimulation
  • Quality Improvement

Grant support

This project was funded by Action Medical Research grant number SP4646. D. C. is supported by the Engineering and Physical Sciences Research Council grant EP/M001393/1. E. S. and T. T. are supported by the James Lewis Foundation (via Great Ormond Street Hospital Children’s Charity) the Child Health Research Appeal Trust. E. S. is funded by University College London Overseas Research Scholarship. T. T. is founded by University College London IMPACT. S. P. is supported by NIHR Biomedical Research founding. S. V. is supported by Swiss National Science Foundation grant SNF 141165. The authors acknowledge the support of the National Institute of Health Research Great Ormond Street Hospital Biomedical Research Centre in performing this work.