title: Optimising EEG-fMRI for Localisation of Focal Epilepsy in Children.
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.
  
  
  RESULTS
  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.
authors.affiliation: Developmental imaging and biophysics Section, Institute of child health, University College London, London, United Kingdom.|Epilepsy Unit, Great Ormond Street Hospital, London, United Kingdom.
authors.forename: Maria
authors.initials: M
authors.lastname: Centeno
authors.affiliation: Developmental imaging and biophysics Section, Institute of child health, University College London, London, United Kingdom.
authors.forename: Tim M
authors.initials: TM
authors.lastname: Tierney
authors.affiliation: Developmental imaging and biophysics Section, Institute of child health, University College London, London, United Kingdom.|Division of Neuroscience, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom.
authors.forename: Suejen
authors.initials: S
authors.lastname: Perani
authors.affiliation: Developmental imaging and biophysics Section, Institute of child health, University College London, London, United Kingdom.
authors.forename: Elhum A
authors.initials: EA
authors.lastname: Shamshiri
authors.affiliation: Epilepsy Unit, Great Ormond Street Hospital, London, United Kingdom.
authors.forename: Kelly
authors.initials: K
authors.lastname: StPier
authors.affiliation: Epilepsy Unit, Great Ormond Street Hospital, London, United Kingdom.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Wilkinson
authors.affiliation: Neurophysiology Department, University Hospital Southampton, Southampton, United Kingdom.
authors.forename: Daniel
authors.initials: D
authors.lastname: Konn
authors.affiliation: Developmental imaging and biophysics Section, Institute of child health, University College London, London, United Kingdom.
authors.forename: Tina
authors.initials: T
authors.lastname: Banks
authors.affiliation: EEG and Epilepsy Unit, Neurology, University Hospitals and Faculty of Medicine of Geneva, Geneva, Switzerland.
authors.forename: Serge
authors.initials: S
authors.lastname: Vulliemoz
authors.affiliation: Department of Clinical and Experimental epilepsy, Institute of Neurology, University College London, London, United Kingdom.
authors.forename: Louis
authors.initials: L
authors.lastname: Lemieux
authors.affiliation: Epilepsy Unit, Great Ormond Street Hospital, London, United Kingdom.
authors.forename: Ronit M
authors.initials: RM
authors.lastname: Pressler
authors.affiliation: Developmental imaging and biophysics Section, Institute of child health, University College London, London, United Kingdom.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Clark
authors.affiliation: Developmental imaging and biophysics Section, Institute of child health, University College London, London, United Kingdom.|Epilepsy Unit, Great Ormond Street Hospital, London, United Kingdom.
authors.forename: J Helen
authors.initials: JH
authors.lastname: Cross
authors.affiliation: Developmental imaging and biophysics Section, Institute of child health, University College London, London, United Kingdom.
authors.forename: David W
authors.initials: DW
authors.lastname: Carmichael
mesh_terms: D000293:Adolescent; D001288:Attention; D001931:Brain Mapping / Q000379:methods; D016022:Case-Control Studies; D002648:Child; D004569:Electroencephalography; D004828:Epilepsies, Partial / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D006801:Humans; D007103:Immobilization; D008279:Magnetic Resonance Imaging; D008297:Male; D009068:Movement; D010775:Photic Stimulation; D058996:Quality Improvement