title: Variability of the hemodynamic response as a function of age and frequency of epileptic discharge in children with epilepsy.
abstract: EEG-fMRI is a non-invasive tool to investigate epileptogenic networks in patients with epilepsy. Different patterns of BOLD responses have been observed in children as compared to adults. A high intra- and intersubject variability of the hemodynamic response function (HRF) to epileptic discharges has been observed in adults. The actual HRF to epileptic discharges in children and its dependence on age are unknown. We analyzed 64 EEG-fMRI event types in 37 children (3 months to 18 years), 92% showing a significant BOLD response. HRFs were calculated for each BOLD cluster using a Fourier basis set. After excluding HRFs with a low signal-to-noise ratio, 126 positive and 98 negative HRFs were analyzed. We evaluated age-dependent changes as well as the effect of increasing numbers of spikes. Peak time, amplitude and signal-to-noise ratio of the HRF and the t-statistic score of the cluster were used as dependent variables. We observed significantly longer peak times of the HRF in the youngest children (0 to 2 years), suggesting that the use of multiple HRFs might be important in this group. A different coupling between neuronal activity and metabolism or blood flow in young children may cause this phenomenon. Even if the t-value increased with frequent spikes, the amplitude of the HRF decreased significantly with spike frequency. This reflects a violation of the assumptions of the General Linear Model and therefore the use of alternative analysis techniques may be more appropriate with high spiking rates, a common situation in children.
authors.affiliation: Neuropediatric Department, Pediatric Hospital, Christian-Albrechts-University, Schwanenweg 20, D-24105 Kiel, Germany; Montreal Neurological Institute and Hospital, McGill University, Montreal, Canada. Electronic address: julia.jacobs@gmx.de.
authors.forename: Julia
authors.initials: J
authors.lastname: Jacobs
authors.affiliation: Montreal Neurological Institute and Hospital, McGill University, Montreal, Canada.
authors.forename: Colin
authors.initials: C
authors.lastname: Hawco
authors.affiliation: Montreal Neurological Institute and Hospital, McGill University, Montreal, Canada.
authors.forename: Eliane
authors.initials: E
authors.lastname: Kobayashi
authors.affiliation: Neuropediatric Department, Pediatric Hospital, Christian-Albrechts-University, Schwanenweg 20, D-24105 Kiel, Germany; Northern German Epilepsy Centre, Christian-Albrechts-University Kiel, Kiel, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Boor
authors.affiliation: Montreal Neurological Institute and Hospital, McGill University, Montreal, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: LeVan
authors.affiliation: Neuropediatric Department, Pediatric Hospital, Christian-Albrechts-University, Schwanenweg 20, D-24105 Kiel, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Stephani
authors.affiliation: Neuropediatric Department, Pediatric Hospital, Christian-Albrechts-University, Schwanenweg 20, D-24105 Kiel, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Siniatchkin
authors.affiliation: Montreal Neurological Institute and Hospital, McGill University, Montreal, Canada.
authors.forename: Jean
authors.initials: J
authors.lastname: Gotman
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography; D004827:Epilepsy / Q000503:physiopathology*; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging; D008297:Male