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Postoperative axonal changes in the contralateral hemisphere in children with medically refractory epilepsy: A longitudinal diffusion tensor imaging connectome analysis.

ABSTRACT: To determine brain plasticity changes due to resective epilepsy surgery in children, we performed a longitudinal connectome analysis on the pattern of axonal connectivity in the contralateral hemisphere. Pre- and postoperative diffusion tensor imaging (DTI) data were acquired from 35 children with intractable focal epilepsy. A total of 54 brain regions of interest (ROIs) were generated in the hemisphere contralateral to the resection. Within a 54 × 54 connectivity matrix, a pairwise connectivity score was calculated for each connection between two ROIs, based on the DTI fiber streamline number in each connection. A permuted Spearman's ?-rank analysis was used to identify specific inter-regional connections showing a significant association between the postoperative change of connectivity score and clinical variables. Nineteen connections in the contralateral hemisphere showed postoperative increases in the strength of connectivity. Postoperative increase in connectivity between insular-inferior frontal operculum regions as well as that between superior frontal orbital and mid frontal orbital regions were both significantly associated with a larger surgical resection volume (? > +0.40) and a younger patient age (? > -0.34). These increases were more robust in patients with frontal resection and in those achieving seizure freedom. Neuropsychological evaluation on subsets of patients revealed that such increases in connectivity were associated with preserved or improved cognitive functions such as visual memory and planning. Resective epilepsy surgery may lead to increased contralateral axonal connectivity in children with focal epilepsy. Our data lead to a hypothesis that such increased connectivity may be an imaging marker of postoperative brain plasticity to compensate for cognitive function. Hum Brain Mapp 37:3946-3956, 2016. © 2016 Wiley Periodicals, Inc.

SUBMITTER: Jeong JW

PROVIDER: S-EPMC5053859 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

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Postoperative axonal changes in the contralateral hemisphere in children with medically refractory epilepsy: A longitudinal diffusion tensor imaging connectome analysis.

Jeong Jeong-Won JW Asano Eishi E Juhász Csaba C Behen Michael E ME Chugani Harry T HT

Human brain mapping 20161101 11

To determine brain plasticity changes due to resective epilepsy surgery in children, we performed a longitudinal connectome analysis on the pattern of axonal connectivity in the contralateral hemisphere. Pre- and postoperative diffusion tensor imaging (DTI) data were acquired from 35 children with intractable focal epilepsy. A total of 54 brain regions of interest (ROIs) were generated in the hemisphere contralateral to the resection. Within a 54 × 54 connectivity matrix, a pairwise connectivity ...[more]

PMID: 27312605

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Project description:BackgroundHybrid PET/MRI can non-invasively improve localization and delineation of the epileptic focus (EF) prior to surgical resection in medically refractory epilepsy (MRE), especially when MRI is negative or equivocal. In this study, we developed a PET-guided diffusion tractography (PET/DTI) approach combining 18F-fluorodeoxyglucose PET (FDG-PET) and diffusion MRI to investigate white matter (WM) integrity in MRI-negative MRE patients and its potential impact on epilepsy surgical planning.MethodsFDG-PET and diffusion MRI of 14 MRI-negative or equivocal MRE patients were used to retrospectively pilot the PET/DTI approach. We used asymmetry index (AI) mapping of FDG-PET to detect the EF as brain areas showing the largest decrease in FDG uptake between hemispheres. Seed-based WM fiber tracking was performed on DTI images with a seed location in WM 3 mm from the EF. Fiber tractography was repeated in the contralateral brain region (opposite to EF), which served as a control for this study. WM fibers were quantified by calculating the fiber count, mean fractional anisotropy (FA), mean fiber length, and mean cross-section of each fiber bundle. WM integrity was assessed through fiber visualization and by normalizing ipsilateral fiber measurements to contralateral fiber measurements. The added value of PET/DTI in clinical decision-making was evaluated by a senior neurologist.ResultsIn over 60% of the patient cohort, AI mapping findings were concordant with clinical reports on seizure-onset localization and lateralization. Mean FA, fiber count, and mean fiber length were decreased in 14/14 (100%), 13/14 (93%), and 12/14 (86%) patients, respectively. PET/DTI improved diagnostic confidence in 10/14 (71%) patients and indicated that surgical candidacy be reassessed in 3/6 (50%) patients who had not undergone surgery.ConclusionsWe demonstrate here the utility of AI mapping in detecting the EF based on brain regions showing decreased FDG-PET activity and, when coupled with DTI, could be a powerful tool for detecting EF and assessing WM integrity in MRI-negative epilepsy. PET/DTI could be used to further enhance clinical decision-making in epilepsy surgery.

Project description:Introduction Determining the full extent of gliomas during radiotherapy planning can be challenging with conventional T1 and T2 magnetic resonance imaging (MRI). The purpose of this study was to develop a method to automatically calculate differences in the fractional anisotropy (FA) and mean diffusivity (MD) values in target volumes obtained with diffusion tensor imaging (DTI) by comparing with values from anatomically homologous voxels on the contralateral side of the brain. Methods Seven patients with a histologically confirmed glioma underwent postoperative radiotherapy planning with 1.5 T MRI and computed tomography. DTI was acquired using echo planar imaging for 20 noncolinear directions with b = 1000 s/mm2 and one additional image with b = 0, repeated four times for signal averaging. The distribution of FA and MD was calculated in the gross tumor volume (GTV), shells 0-5 mm, 5-10 mm, 10-15 mm, 15-20 mm, and 20-25 mm outside the GTV, and the GTV mirrored in the left-right direction (mirGTV). All images were aligned to a template image, and FA and MD interhemispheric difference images were calculated. The difference in mean FA and MD between the regions of interest was statistically tested using two-sided paired t-tests with ? = 0.05. Results The mean FA in mirGTV was 0.20 ± 0.04, which was larger than the FA in the GTV (0.12 ± 0.03) and shells 0-5 mm (0.15 ± 0.03) and 5-10 mm (0.17 ± 0.03) outside the GTV. The mean MD (×10-3 mm2/s) in mirGTV was 0.93 ± 0.09, which was smaller than the MD in the GTV (1.48 ± 0.19) and the peritumoral shells. The distribution of FA and MD interhemispheric differences followed the same trends as FA and MD values. Conclusions This study successfully implemented a method for calculation of FA and MD differences by comparison of voxel values with anatomically homologous voxels on the contralateral side of the brain. Further research is warranted to determine if radiotherapy planning using these images can be used to improve target delineation.

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Postoperative axonal changes in the contralateral hemisphere in children with medically refractory epilepsy: A longitudinal diffusion tensor imaging connectome analysis.

Publications

Postoperative axonal changes in the contralateral hemisphere in children with medically refractory epilepsy: A longitudinal diffusion tensor imaging connectome analysis.

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