Normative Brain Mapping of Scalp EEG to Localise Epileptic Foci for Epilepsy Surgery

Introduction and Background
Epilepsy is a relatively common disabling neurological disorder (de Boer et al. 2008), characterised by persistent and unprovoked seizure generation (Beghi, 2020). An estimated 50 million patients worldwide suffer from all forms of epilepsy, and approximately one third of epilepsy patient population do not obtain seizure-control through medication (Kwan and Brodie et al. 2000).

Available medication is effective in some cases. However, for patients with pharmacoresistant focal epilepsy, brain surgery holds the best chance of achieving seizure freedom and improving quality of life (Fitzgerald et al. 2021). Consideration for surgery is a highly selective process. It involves a clinical evaluation and the use of several imaging modalities in order to identify the epileptic foci and to determine epilepsy type. In addition, a significant portion of patients present with complex cases or contradicting results between different modalities, and are not considered for surgery (Engel et al. 2003). Furthermore, despite advances in imaging and surgical experience, many candidates who undergo epilepsy surgery do not achieve complete seizure freedom (Nowell et al. 2014). Most often in this case, epileptic foci were not accurately identified, leading to seizure recurrence postoperatively. Collectively, contradicting clinical results and poor localisation of the epileptic foci constitutes a big problem. It is therefore vital to improve the concordance between different imaging modalities, to strengthen surgical success.

Non-invasive techniques used for epilepsy evaluation include; scalp electroencephalography (EEG), magnetic resonance imaging (MRI), magnetoencephalography (MEG), positron emission tomography (PET) and more (Fitzgerald et al. 2021). Similarly, some candidates require a more detailed analysis and planning using invasive techniques such as intracranial electroencephalography (iEEG), which may propose surgical complications (Arya et al. 2013, Blauwblomme et al, 2011). Many of these techniques are geographically undesirable due to accessibility and cost issues. Therefore, the use of epilepsy surgery in developing countries remains limited (Wieser, 1998). Alternatively, scalp EEG is a low-cost, versatile and portable imaging tool that offers excellent temporal resolution and effective collaboration with other imaging modalities (Fitzgerald et al. 2021, LaRocco et al, 2020, Michel and Brunet, 2019). The key goal of this project is to study localisation of epileptic foci using scalp EEG in epilepsy surgery, via computational brain modelling, which has potential to be used worldwide.

Data, Methodology and Progress
The pre-collected data to be used for this PhD is provided by partnership with UCL and UCLH. The EEG dataset clnsists of 62 patients and 18 healthy controls, with further 5-10 segments per each candidate. The segments include a range of resting-state, task of simultaneous EEC and fMRI recordings, lasing 5.84-1887.86 seconds. Most of the segments include 32 or 64 channels and a sampling rate of 5000Hz.