Abstracts

Rationale: Although neuroanatomical abnormalities are often observed in individuals with medically intractable epilepsy undergoing assessment for epilepsy surgery, less is known about how often brain abnormalities are observed in newly diagnosed focal epilepsy cases. In this study we qualitatively assessed baseline brain MRI in participants in the Human Epilepsy Project (HEP), a multi-center study of newly diagnosed focal epilepsy. Methods: Participants in the HEP study receive an MRI scan close to study enrollment, consisting of a standardized whole brain T1-weighted MRI acquisition, FLAIR imaging and T2-weighted acquisitions. Each MRI scan was visually assessed by an experienced epileptologist blind to the participants clinical history. Imaging features were recorded using NINDS common data elements. Results: Imaging assessments were carried out in 406 subjects; N = 242 female, 160 male, 4 sex not specified, age = 33 ± 13.92 years. Scans were assessed as abnormal in 158 participants (38.9%), normal in 230 participants (56.6%) and incidental findings were observed in 18 cases (4.4%). Neuroanatomical abnormalities were more common in men than women (male: 49%; female: 33%, p = 0.002). The most commonly observed abnormality was enlarged ventricles in association with diffuse brain atrophy; N = 85 cases (21%). Other frequently observed abnormalities include temporal lobe morphological changes without clear features of hippocampal sclerosis in N = 42 cases (10.3%); these changes were most commonly hippocampal malrotation or dysgenesis. Likely hippocampal sclerosis was observed in 10 subjects (2.5%). Low-grade tumors were observed in 14 subjects (3.4%). Heterotopic GM and other malformations of cortical development were observed in 12 cases (2.9%). Isolated findings included corpus callosum agenesis (N = 2), cerebellar hypoplasia (N = 4) and basal ganglia calcification (N = 3). Conclusions: Most individuals with newly diagnosed focal epilepsy do not have focal brain abnormalities detected using visual inspection of whole brain 3T MRI. Previous reports identify a larger proportion of neuroanatomical differences ie. lesional cases > 50% in medically intractable cohorts. Our findings suggest that intractable focal epilepsy is associated with a greater proportion of lesions compared with individuals with adequate seizure control using medication. The HEP study is tracking health outcomes so we will be able to address this hypothesis in the future. The higher proportion of neuroanatomical abnormalities in males compared to females in this cohort is an interesting observation. The reason for this gender difference is currently unclear. Funding: Epilepsy Study Consortium (ESCI), a non-profit organization accelerating development of new epilepsy therapies; ESCI is supported by industry, philanthropy and foundations.