Epilepsy Surgery for Focal Cortical Dysplasia: Clinicopathological Correlates and Advances in Neuroimaging

Abstract

This thesis describes a series of studies about patients with pharmacoresistant epilepsy caused by a malformation of cortical development called ‘Focal Cortical Dysplasia (FCD)’, who are evaluated for epilepsy surgery. These patients typically have frequent epileptic seizures from young age onwards. Surgery can be a therapeutic option, entailing the removal of the aberrant area of the brain that is the source of seizures. In our study half of the patients reached lasting seizure-freedom after surgery, with lower chances in patients with the histologically least pronounced subtype minimal malformation of cortical development (mMCD). We also found differences in clinical presentation between subtypes. Patients undergoing epilepsy surgery for FCD before the age of 18 years, had a better cognitive outcome when their duration of epilepsy, between onset of seizures and surgery, was shorter. Of these patients, 24% showed improvement in cognitive functioning following surgery. The subtle structural brain abnormalities in FCD are often difficult or impossible to detect using current standard imaging techniques. This negatively affects the chance of favourable seizure outcome or even excludes surgery as a treatment option. Care for epilepsy patients can greatly benefit from improving pre-surgical imaging. We showed that the use of a new, high-field MRI technique, 7 tesla MRI, led to identification of lesions in 23% of the patients in whom previous standard MRI did not reveal a possible lesion. Surgical treatment confirmed the presence of an mMCD/FCD. High-field 7T MRI can improve decision-making and selection of candidates for epilepsy surgery, particularly when conventional MRI reveals no abnormalities.