Network analysis of EEG related functional MRI changes due to medication withdrawal in focal epilepsy

Hermans, Kees; Ossenblok, Pauly; Houdt, Petra J. van; Geerts, Liesbeth; Verdaasdonk, Rudolf M.; Boon, Paul; Colon, Albert; Munck, Jan C. de

doi:10.1016/j.nicl.2015.06.002

Cited by 19 publications

(14 citation statements)

References 47 publications

(59 reference statements)

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“…FC maps could be influenced by AEDs and other clinical factors (i.e., cognitive impairment). In our case, AEDs were too heterogeneous to be studied in detail . Nevertheless, our analysis focused on the effect of IEDs on connectivity maps seeded from the presumed EZ.…”

Section: Discussionmentioning

confidence: 97%

Epileptic networks are strongly connected with and without the effects of interictal discharges

Iannotti

Grouiller

Centeno³

et al. 2016

Epilepsia

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SUMMARYObjective: Epilepsy is increasingly considered as the dysfunction of a pathologic neuronal network (epileptic network) rather than a single focal source. We aimed to assess the interactions between the regions that comprise the epileptic network and to investigate their dependence on the occurrence of interictal epileptiform discharges (IEDs). Methods: We analyzed resting state simultaneous electroencephalography-functional magnetic resonance imaging (EEG-fMRI) recordings in 10 patients with drug-resistant focal epilepsy with multifocal IED-related blood oxygen level-dependent (BOLD) responses and a maximum t-value in the IED field. We computed functional connectivity (FC) maps of the epileptic network using two types of seed: (1) a 10-mm diameter sphere centered in the global maximum of IED-related BOLD map, and (2) the independent component with highest correlation to the IED-related BOLD map, named epileptic component. For both approaches, we compared FC maps before and after regressing out the effect of IEDs in terms of maximum and mean t-values and percentage of map overlap. Results: Maximum and mean FC maps t-values were significantly lower after regressing out IEDs at the group level (p < 0.01). Overlap extent was 85% AE 12% and 87% AE 12% when the seed was the 10-mm diameter sphere and the epileptic component, respectively. Significance: Regions involved in a specific epileptic network show coherent BOLD fluctuations independent of scalp EEG IEDs. FC topography and strength is largely preserved by removing the IED effect. This could represent a signature of a sustained pathologic network with contribution from epileptic activity invisible to the scalp EEG.

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Section: Discussionmentioning

confidence: 97%

Epileptic networks are strongly connected with and without the effects of interictal discharges

Iannotti

Grouiller

Centeno³

et al. 2016

Epilepsia

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“…Withdrawing antiepileptic medications during inpatient EEG‐video monitoring enables this step to be taken safely in a medically supervised environment (considering the risk of provoking frequent or prolonged seizures) and allows these medication‐reduced EEG‐fMRI studies to be performed without ethical concerns . Organizing such studies at short notice can be a logistical challenge, due to MR scanner unavailability and timely MRI safety clearance. This can be overcome by the weekly scheduled timeslot for inpatient EEG‐fMRI studies.…”

Section: Discussionmentioning

confidence: 99%

Clinical benefit of presurgical EEG‐fMRI in difficult‐to‐localize focal epilepsy: A single‐institution retrospective review

et al. 2019

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Objective: The aim of this report is to present our clinical experience of electroencephalography-functional magnetic resonance imaging (EEG-fMRI) in localizing the epileptogenic focus, and to evaluate the clinical impact and challenges associated with the use of EEG-fMRI in pharmacoresistant focal epilepsy. Methods: We identified EEG-fMRI studies (n = 118) in people with focal epilepsy performed at our center from 2003 to 2018. Participants were referred from our Comprehensive Epilepsy Program in an exploratory research effort to address often difficult clinical questions, due to complex and difficult-to-localize epilepsy. We assessed the success of each study, the clinical utility of the result, and when surgery was performed, the postoperative outcome. Results: Overall, 50% of EEG-fMRI studies were successful, meaning that data were of good quality and interictal epileptiform discharges were recorded. With an altered recruitment strategy since 2012 with increased inclusion of patients who were inpatients for video-EEG monitoring, we found that this patients in this selected group were more likely to have epileptic discharges detected during EEG-fMRI (96% of inpatients vs 29% of outpatients, P<.0001). To date, 48% (57 of 118) of patients have undergone epilepsy surgery. In 10 cases (17% of the 59 successful studies) the EEG-fMRI result had a "critical impact" on the surgical decision. These patients were difficult to localize because of subtle abnormalities, apparently normal MRI, or extensive structural abnormalities. All 10 had a good seizure outcome at 1 year after surgery (mean follow-up 6.5 years). Significance: EEG-fMRI results can assist identification of the epileptogenic focus in otherwise difficult-to-localize cases of pharmacoresistant focal epilepsy. Surgery determined largely by localization from the EEG-fMRI result can lead to good seizure outcomes. A limitation of this study is its retrospective design with nonconsecutive recruitment. Prospective clinical trials with well-defined inclusion criteria are needed to determine the overall benefit of EEG-fMRI for preoperative localization and postoperative outcome in focal epilepsy. K E Y W O R D SEEG, epilepsy surgery, fMRI, focal epilepsy 50 | KOWALCZYK et AL. SUPPORTING INFORMATIONAdditional supporting information may be found online in the Supporting Information section.

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“…Interestingly, previous studies have explored the influence of AEDs on functional connectivity, and found a significant correlation [Hermans et al, 2015]. Therefore, it would be interesting for future analyses to determine the interaction between medication, IEDs and the subsequent effect on connectivity.…”

Section: Transient and Non-transient Effects Of Iedsmentioning

confidence: 99%

Interictal activity is an important contributor to abnormal intrinsic network connectivity in paediatric focal epilepsy

Shamshiri¹,

Tierney²,

Centeno³

et al. 2016

Human Brain Mapping

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Patients with focal epilepsy have been shown to have reduced functional connectivity in intrinsic connectivity networks (ICNs), which has been related to neurocognitive development and outcome. However, the relationship between interictal epileptiform discharges (IEDs) and changes in ICNs remains unclear, with evidence both for and against their influence. EEG-fMRI data was obtained in 27 children with focal epilepsy (mixed localisation and aetiologies) and 17 controls. A natural stimulus task (cartoon blocks verses blocks where the subject was told "please wait") was used to enhance the connectivity within networks corresponding to ICNs while reducing potential confounds of vigilance and motion. Our primary hypothesis was that the functional connectivity within visual and attention networks would be reduced in patients with epilepsy. We further hypothesized that controlling for the effects of IEDs would increase the connectivity in the patient group. The key findings were: (1) Patients with mixed epileptic foci showed a common connectivity reduction in lateral visual and attentional networks compared with controls. (2) Having controlled for the effects of IEDs there were no connectivity differences between patients and controls. (3) A comparison within patients revealed reduced connectivity between the attentional network and basal ganglia associated with interictal epileptiform discharges. We also found that the task activations were reduced in epilepsy patients but that this was unrelated to IED occurrence. Unexpectedly, connectivity changes in ICNs were strongly associated with the transient effects of interictal epileptiform discharges. Interictal epileptiform discharges were shown to have a pervasive transient influence on the brain's functional organisation. Hum Brain Mapp 38:221-236, 2017. © 2016 Wiley Periodicals, Inc.

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Network analysis of EEG related functional MRI changes due to medication withdrawal in focal epilepsy

Cited by 19 publications

References 47 publications

Epileptic networks are strongly connected with and without the effects of interictal discharges

Epileptic networks are strongly connected with and without the effects of interictal discharges

Clinical benefit of presurgical EEG‐fMRI in difficult‐to‐localize focal epilepsy: A single‐institution retrospective review

Interictal activity is an important contributor to abnormal intrinsic network connectivity in paediatric focal epilepsy

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