Determinants of IQ outcome after focal epilepsy surgery in childhood: A longitudinal case‐control neuroimaging study

Abstract

Summary Objective Intelligence quotient (IQ) outcomes after pediatric epilepsy surgery show significant individual variation. Clinical factors such as seizure cessation or antiepileptic medication discontinuation have been implicated, but do not fully account for the heterogeneity seen. Less is known about the impact of neurobiological factors, such as brain development and resection location. This study examines clinical and neuroimaging factors associated with cognitive outcome after epilepsy surgery in childhood. Methods Fifty‐two children (28 boys, 24 girls) were evaluated for epilepsy surgery and reassessed on average 7.7 years later. In the intervening time, 13 were treated pharmacologically and 39 underwent focal surgery (17 temporal, 16 extratemporal, six multilobar; mean age at surgery = 14.0 years). Pre‐ and postsurgical assessments included IQ tests and T1‐weighted brain images. Predictors of IQ change were investigated, including voxel‐based analyses of resection location, and gray and white matter volume change. Results Overall modest IQ improvement was seen in children treated surgically, but not in those treated pharmacologically only. Applying a ≥10‐point change threshold, 39% of the surgically treated children improved, whereas 10% declined. Clinical factors associated with IQ increases were lower preoperative IQ and longer follow‐up duration, whereas seizure and antiepileptic medication cessation were not predictive. Among neuroimaging factors, we observed that left anterior temporal resections impacted negatively on verbal reasoning, linked to full‐scale IQ decline. In contrast, gray matter volume change in ipsi‐ and contralesional hemispheres was positively correlated with IQ change. Voxel‐based morphometry identified the gray matter volume change in the contralesional dorsolateral frontal cortex as most strongly associated with IQ improvement. Significance We show that a variety of factors are likely to contribute to patterns of postsurgical change in IQ. Neuroimaging results indicate that left anterior temporal resections constrain development of verbal cognition, whereas simultaneously cortical growth after surgical treatment can support improvements in IQ.

Concordance Between Transcranial Magnetic Stimulation and Functional Magnetic Resonance Imaging (MRI) Derived Localization of Language in a Clinical Cohort

“…Young children form one such group, [46][47][48] in whom cortical stimulation mapping risks are significant (ie, after discharges and seizures due to higher amperage threshold 49 ) with only a 50% success rate in children under 10 years 50 and both functional MRI and magnetoencephalography fail in *30%. 51,52 The lack of comprehensive language mapping for them frequently prevents timely surgeries that could significantly improve cognitive function 53 and quality of life 48,54 or surgery proceeds without a good language map, with increased risk of postoperative language deficits. 55 For these children and other patients in whom functional MRI and other methods are not successful, TMS is especially promising.…”

Clinical Utility of Transcranial Magnetic Stimulation (TMS) in the Presurgical Evaluation of Motor, Speech, and Language Functions in Young Children With Refractory Epilepsy or Brain Tumor: Preliminary Evidence

“…Because children in this age group are sedated during fMRI and MEG and in instances when mapping is successful, it is limited to localization of receptive language areas ( 27 ). The lack of thorough speech and language localization for this group likely prevents timely surgeries that could significantly improve cognitive function ( 28 ) and quality of life ( 15 , 23 ); in other cases, surgery proceeds without a precise language map, resulting in possible post-operative speech and language deficits ( 29 ) or inadequate resection. However, when compared to fMRI and MEG, TMS has many advantages.…”

Seizures and Epilepsy in Childhood

“…It has been documented that an early withdrawal of antiseizure medications after epilepsy surgery is generally feasible, associated with an improvement in IQ and psychomotor development, and strongly preferred by parents 60 . Furthermore, 2019 data show that complete medication withdrawal can also occur in a number of children under ketogenic diet treatment, at least during treatment with the diet 67 .…”