Concordance of MRI lesions and EEG focal slowing in children with nonsyndromic epilepsy

Summary Purpose To investigate the significance of electroencephalography ( EEG ) focal slowing in children with epilepsy and to determine the correlation between focal slowing and focal lesions on brain magnetic resonance imaging ( MRI ). Methods We reviewed 5,149 EEG and 22,543 MRI reports for children who visited our institution from 2000 to 2010. Patients with nonsyndromic epilepsy (n = 253) were divided into groups with: focal slowing without any interictal epileptiform discharge ( IED ) (group 1); focal IED s without focal slowing (group 2); focal slowing and focal IED (group 3); and normal findings (group 4). Focal slowing and MRI lesions were categorized by location, side, and depth. Key Findings We found MRI abnormalities in 59% of subjects in group 1, 56% in group 2, 74% in group 3, and 27% in group 4 (p < 0.0001). Cortical malformation ( CM ) was the most common pathology in groups with focal slowing. Focal slowing often correlated with the laterality of the MRI lesion (61–70%), but the location was concordant in only 40%. The associated lesions rarely were exclusively confined to the centrum semiovale (18%). Significance Focal slowing in children with epilepsy is highly associated with focal structural lesions on MRI , most commonly CM , and usually involves multiple layers. Focal slowing, as well as focal interictal epileptiform activity, is an important and useful EEG indicator of a brain structural abnormality in children with nonsyndromic epilepsy.