Abstracts

Rationale: The aim of this study was to investigate neuroanatomical correlates of depression and anxiety symptoms in individuals with new onset focal epilepsy of unknown etiology who have been enrolled in the Human Epilepsy Project.Methods: HEP participants were screened at enrollment for depression symptoms with the Neurologic Depression Disorder Inventory in Epilepsy (NDDIE) and the Center of Epidemiologic Studies Depression (CESD), and for anxiety using the Generalized Anxiety Disorder – 7 (GAD7). Cutoff scores of NDDIE > 15 and CESD > 15 were used to categorize individuals with depression symptoms. The following anxiety categories were derived from GAD7 scores: minimal, < 4; mild, 5 – 9, moderate; 10 – 14; and severe, > 15. All participants had a 1mm isotropic whole brain T1 weighted MRI. Images were processed using Freesurfer v5.3. Hippocampal and amygdala volume, and frontal, temporal, occipital and parietal lobe thickness were compared in the categories described above.Results: 129 adults with new onset epilepsy of unknown etiology completed depression and anxiety screening and MRI. There was a consistent pattern of decreased cortical thickness across cortical lobes in individuals with higher scores on the NDDIE and CESD depression screening instruments. The strongest differences were observed in the left and right parietal lobes (cortical thickness reduction 0.06 – 0.1 mm, p = 0.03 – 0.004). Right frontal lobe cortical thickness was also reduced in individuals with high NDDIE scores (0.09 mm, p = 0.04). No hippocampal or amygdala volume differences were observed in relation to the NDDIE or CESD categories. Individuals with severe anxiety had increased amygdala volume (218 mm3, p = 0.055). No significant differences in cortical thickness were observed in the anxiety categories.Conclusions: We have identified patterns of neuroanatomical differences, comprising reduced parietal lobe and right frontal cortical thickness, in individuals with high scores on depression screening instruments administered at study enrollment. Individuals who score highly on anxiety screening have subtle increases in amygdala volume. Our findings suggest that differing patterns of brain changes in adults with focal epilepsy may be associated with these two common epilepsy comorbidities. Whether these findings may be associated with an increased risk of treatment-resistant epilepsy need to be investigated. Because similar neuroanatomical differences have been reported in patients with primary mood and anxiety disorders, it is unclear whether the observed depression or anxiety symptoms can be attributed to seizures. The longitudinal component of the HEP study, including follow up MRI, depression and anxiety symptom assessments, and seizure tracking, will assist in answering this question since seizure frequency will vary between the participants. Supported by The Epilepsy Study Consortium (ESCI). The funding provided to ESCI comes from UCB Pharma, Pfizer, Eisai, Lundbeck, Finding A Cure for Epilepsy and Seizures, The Andrews Foundation, Friends of Faces and others.