Longitudinal structural change of gray matter before and after hemispherotomy

BackgroundHemispherotomy is an effective surgery developed to treat refractory epilepsy caused by diffuse unihemispheric pathologies. Post-surgery neuroplastic mechanisms supporting behavioral recovery after left and right hemispherotomy as well as their difference remain largely unclear. MethodsIn a large cohort of 57 pediatric patients who underwent hemispherotomy, voxel-wise GMV in unaffected regions (contralesional cerebrum and bilateral cerebellum) and behavioral abilities were assessed before and after surgery. Using linear mixed models, we evaluated changes in GMV and behavioral scores, and how GMV changes correlated with improvements in behavioral scores. In addition, three machine learning regression algorithms were applied to assess whether preoperative GMV can predict postoperative behavior. ResultsIn the two patient groups (29 left hemispherotomy patients, age of surgery mean {+/-} standard deviation = 3.5 {+/-} 2.5; 28 right hemispherotomy patients, age of surgery 4.6 {+/-} 2.5), widespread increases in the postoperative GMV in the contralateral cerebrum and ipsilateral cerebellum but decreases in the postoperative GMV in the contralateral cerebellum were consistently observed. Importantly, the decrease in GMV in the contralateral cerebellum was significantly correlated with improvement in behavioral scores in right but not left hemispherotomy patients. Moreover, the preoperative GMV around the most longitudinally changed locations significantly predicted postoperative behavioral scores in left but not right hemispherotomy patients. ConclusionsOur findings indicate an important role for the contralateral cerebellum in the recovery after right hemispherotomy, and postoperative behavioral scores can be predicted with preoperative GMV features. What is already known on this topicThe contralesional cerebrum plays a key role in the recovery after hemispherotomy. What this study addsDespite suffering from gray matter atrophy, GMV decrease in contralesional cerebellum is associated with improvement in behavioral score in patients after hemispherotomy. How this study might affect research, practice or policyThese results provide novel insight into the prominence of the contralateral cerebellum in the recovery after hemispherotomy and highlight the clinical role of presurgery GMV in the prediction of postsurgery behavior.