Abstracts

Rationale: BECTS is one of the most common focal electroclinical epilepsy syndromes occurring in childhood. Distinctive features of BECTS include its specific EEG signature, seizure semiology, and age at onset, in an otherwise developmentally normal child. The structural MRI is virtually always lesion negative, based on standard visual interpretation. We use cortical thickness analysis of high resolution whole-brain MRI to investigate subtle regional structural variations in brains of children with BECTS compared to controls. These analyses may reveal structural correlates of the functional changes that define this disorder.Methods: Nine BECTS subjects (mean age 15.8 2.3 years) and 32 neurologically normal controls (mean age 16.8 4 years) were included in the study. Subjects were imaged on a Siemens Sonata 1.5 T MRI scanner using a coronal T1-weighted whole-brain MPRAGE acquisition, TR 1730 ms, TE 4.38 ms, TI 1100 ms, FA 15 , voxel resolution 0.94 mm2 in-plane, slice thickness 1.6 mm. MRI scans were processed using the default Freesurfer processing stream (http://surfer.nmr.mgh.harvard.edu/, version 5.0). Cortical thickness maps were coregistered to the supplied fsaverage template, smoothed using a 10mm surface-based smoothing filter and vertex-wise comparisons between BECTS and controls were undertaken, including age as a covariate of no interest in the statistical model. Significant thickness differences were identified using a threshold of p < 0.05, using false discovery rate to correct for multiple comparisons. The mean cortical thickness difference between BECTS and controls was estimated at vertices deemed significant by the previously described criteria.Results: Bilateral cortical gray matter thickness increases were observed in the BECTS subjects. The most significant increases in gray matter thickness were primarily located in the frontal lobe. Specific areas of increase included the middle frontal gyrus, Brocas area and the supramarginal gyrus. More diffuse regional thickness increases were observed in the parietal lobe bilaterally. A small region of decreased cortical thickness was identified in the right postcentral sulcus. Comparison of the cortical thickness in these regions suggested that the abnormality manifests as an average increase of 0.41 mm in the BECTS cohort.Conclusions: The presence of subtle cortical thickening in BECTS patients may be interpreted as mild regional dysplasia. This points towards an altered neurodevelopmental pathway in BECTS patients, which may be part of the pathophysiology of this form of epilepsy.