Cortical Thickness Asymmetries in MRI-Abnormal Pediatric Epilepsy Patients: A Potential Metric for Surgery Outcome

Neuroanatomical morphometric analysis in childhood epilepsy reveals patterns of widespread cortical thinning. The degree of neocortical thinning both ipsilateral and contralateral to the focus is associated with poor epilepsy surgery outcome for MRI-normal adult epilepsy as well as MRI-abnormal childhood epilepsy. We examined if differences in cortical thickness (CT) were related to where focus of epilepsy was located. Sagittal T1-weighted MPRAGE structural MRI scans were performed on 25 pediatric epilepsy patients (age: 7-17 years) with abnormalities on MRI. Morphometric processing and analyses were conducted using FreeSurfer 6.0. A repeated measures ANOVA was used to examine the effects of focus (temporal or extratemporal), side (ipsilateral or contralateral), and lobe (frontal, temporal, parietal, occipital) on CT. Bivariate correlations were conducted to examine the relationship between CT and patients’ age of onset and duration of epilepsy. Repeated measures ANOVA revealed a significant effect of lobe (p\u3c.01) such that temporal CT\u3e frontal CT\u3e occipital CT\u3e parietal CT. Post-hoc analysis showed that parietal lobe CT was significantly less than the frontal and temporal lobes. Across both temporal and extratemporal groups, we found that the temporal lobe was the thickest on the ipsilateral side. This may be because the MRI abnormality, which was largely dysplasia, contributed to a greater CT. Seizure onset and duration was also associated with thinning of the ipsilateral parietal lobe (r=-0.401; p\u3c.05) suggesting that perhaps the parietal lobe is vulnerable to long-term effects of ongoing seizure activity. As the majority of this sample (84%) were noted to have successful surgery outcomes, as quantified by an Engel Class 1 or 2 designation post-surgery, our results are also in accordance with previous research which suggests that thicker ipsilateral CT is associated with a good surgery outcome