Understanding haemodynamic changes surrounding epileptic events in children

• Main Author: Shamshiri, E. A.
• Other Authors: Carmichael, D. W. ; Cross, H.
• Published: University College London (University of London) 2017
• Subjects: 618.92
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.746479

The interrelationship between cerebral haemodynamics and epileptic activity has been the subject of study for over 100 years. The overall goal of this PhD is to use and develop multimodal imaging to better understand this relationship in a paediatric population. This has important implications for the localisation of epileptic activity that can aid pre-surgical evaluation and seizure detection. The benefit of interictal epileptiform discharge (IED) suppression in clinical treatment is under debate, considering little is known about their impact on cognitive function. By applying EEG-fMRI, it was found that transient effects of IEDs were responsible for connectivity differences between patients and controls, showing the widespread impact of IEDs on BOLD signal and suggesting the importance of IED suppression for normal functional connectivity. Haemodynamic changes may occur prior to epileptic event onset. Therefore we evaluated the response function (HRF) to IEDs in paediatric focal epilepsy patients, as an HRF was created from simultaneous EEG-fMRI data and found to be beneficial in the delineation of epileptic foci. However, the underlying neurovascular changes seen in this altered HRF still needed to be explored. Therefore EEG-NIRS was utilised to interpret the mechanistic changes found in BOLD during IEDs. NIRS provides the added information of concentration changes of both –oxy and –deoxy haemoglobin rather than relative changes in deoxyhaemoglobin. To perform these experiments a new optode holder applicable to the clinical environment had to be made and tested for efficacy. The best design was a flexible optode grid, as it required no interference with the standard clinical protocol. Once tested in patients, EEG-NIRS found pre-ictal/pre-IED increases in oxygen saturation and oxyhaemoglobin concentrations, thereby corroborating with prior haemodynamic changes seen in EEG-fMRI. Therefore, by utilizing both EEG-fMRI and EEG-NIRS a greater understanding of the haemodynamic changes surrounding epileptic events in children can be obtained.