Mapping brain networks in patients with epilepsy using fMRI-EEG

Louis Lemieux
University College London

Epilepsy is the most common serious neurological condition, affecting all ages, and one of most important contributors to the global burden of disease. Uncontrolled seizures and the side effects of anti-epileptic drugs are the key quality of life determinants for individuals with epilepsy. The identification and characterisation of the networks responsible for human epileptic seizures is crucial to allow us to eliminate seizures. However it remains an unresolved challenge in most cases despite complex and expensive tests. I will present the results of our investigations into the haemodynamic correlates and electrical generators of epileptic activity such as interictal spikes and seizures in humans. Using (scalp and intracranial) EEG and fMRI data recorded simultaneously we are uniquely able to map activity patterns over the entire brain. We start with a brief overview of technical challenges and solutions for simultaneous acquisitions, in particular with intracranial EEG. In generalised epilepsy the question of the relationship between localisation, connectivity and altered consciousness is of particular interest, as is the nature of the generators of widespread EEG changes. We show how advanced data analysis and modelling methods have shed new light on these issues. In patients with focal epilepsy, the problem of localisation generally has a more direct clinical relevance and is focused on identifying the origin of the epileptic seizures. However, the study of focal interictal discharges using fMRI is facilitated by a number of practical considerations; we will show some EEG-fMRI patterns which suggest potentially clinically useful markers. Although more challenging, the study of seizures in humans offers a great opportunity to shed new light on the condition’s defining feature and therefore to address the most pressing questions such as, how do seizures begin and propagate?

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