Morphometrics of the preserved post-surgical hemisphere in pediatric drug-resistant epilepsy
Authors: Granovetter Michael C. , Maallo Anne Margarette S. , Patterson Christina , Glen Daniel , Behrmann Marlene 
Published: September 2023

AbstractImportanceStructural integrity of cortex following cortical resection for epilepsy management has been previously characterized, but only in adult patients.ObjectiveThis study sought to determine whether morphometrics of the preserved hemisphere in pediatric cortical resection patients differ from non-neurological controls.DesignThis was a case-control study, from 2013-2022.SettingThis was a single-site study.Participants32 patients with childhood epilepsy surgery and 51 age- and gender-matched controls participated.Main Measure(s)We quantified morphometrics of the preserved hemisphere at the level of gross anatomy (lateral ventricle size, volume of gray and white matter). Additionally, cortical thickness, volume, and surface area were measured for 34 cortical regions segmented with the Desikan-Killiany atlas, and, last, volumes of nine subcortical regions were also quantified.Results13 patients with left hemisphere (LH) surgery and a preserved right hemisphere (RH) (median age/median absolute deviation of age: 15.7/1.7 yr; 6 females, 7 males) and 19 patients with RH surgery and a preserved LH (15.4/3.7 yr; 11 females, 8 males) were compared to 51 controls (14.8/4.9 yr; 24 females, 27 males). Patient groups had larger ventricles and reduced total white matter volume relative to controls, and only patients with a preserved RH, but not patients with a preserved LH, had reduced total gray matter volume relative to controls. Furthermore, patients with a preserved RH had lower cortical thickness and volume and greater surface area of several cortical regions, relative to controls. Patients with a preserved LH had no differences in thickness, volume, or area, of any of the 34 cortical regions, relative to controls. Moreover, both LH and RH patients showed reduced volumes in select subcortical structures, relative to controls.Conclusions and RelevanceThat left-sided, but not right-sided, resection is associated with more pronounced reduction in cortical thickness and volume and increased cortical surface area relative to typically developing, age-matched controls suggests that the preserved RH undergoes structural plasticity to an extent not observed in cases of right-sided pediatric resection. Future work probing the association of the current findings with neuropsychological outcomes will be necessary to understand the implications of these structural findings for clinical practice.Key PointsQuestionFollowing large pediatric cortical resection for the treatment of drug-resistant epilepsy, how does the structural integrity of the preserved hemisphere differ from that of healthy children?FindingsIn this case-control study of 32 patients with childhood epilepsy surgery, left-sided—but not right-sided—resection cases showed significantly reduced cortical volume and thickness and increased surface area relative to 51 non-neurological matched controls.MeaningThere is reorganization of the right hemisphere that is specific to left hemispheric resection but not vice versa; this is potentially a consequence of unique left-lateralized functions (e.g., language) requiring postoperative remapping to the right hemisphere.