Computational protocol: Temporal lobe surgery in childhood and neuroanatomical predictors of long-term declarative memory outcome

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Protocol publication

[…] Manual tracing of brain volumes of interest was carried out in the software package MRIcron (C. Rorden, http://www.mccauslandcenter.sc.edu/mricro/mricron/), with reference to the contralesional hemisphere. Measurements included presurgical DNT lesion volumes, post-surgical resection cavity volumes (resection volume), and pre- and post-surgical hippocampal volumes. Hippocampal volumes were measured by manual tracing on coronal images. Measurements included the uncus, and were delineated by anatomical boundaries: the white matter tract of the subiculum, choroid plexus, the lateral ventricle and the alveus as borders, which were not included. To ascertain reliability of hippocampal volumes, ratings for 28 hippocampi were repeated independently by a trained research assistant, showing excellent reliability (Cronbach’s alpha = 0.992).A rating system of temporal lobe integrity devised by was applied to code post-surgical tissue integrity in the temporal lobe. Using the intact brain hemisphere as reference, MRI images were tilted until the sylvian fissure appeared horizontal from a sagittal view. Structural limits of temporal lobe were then defined using coronal markers in the intact hemisphere (Supplementary Fig. 1): the temporal pole was defined as extending from the most anterior part of the temporal lobe to the slice preceding the frontotemporal junction; the remaining temporal lobe structures were defined as extending from the frontotemporal junction up to the coronal slice abutting the splenium of the corpus callosum. Tissue integrity was coded independently within five temporal lobe structures: the superior, middle and inferior temporal gyri, temporal pole and mesial region, including the parahippocampal gyrus and hippocampus. Tissue integrity was coded slice by slice moving from anterior to posterior: 1 = total resection, 2 = partial resection (at least one-third of tissue missing), 3 = predominantly intact (less than one-third of tissue missing), and 4 = fully intact. To control for interindividual differences in the length of the temporal lobes, ratings for superior temporal gyrus, middle temporal gyrus, inferior temporal gyrus and mesial region were summed in anterior, middle and posterior thirds and structural integrity was expressed as the proportion of the maximal possible rating. [...] Language lateralization was examined at follow-up using functional MRI. A reliable and well-validated semantic retrieval task was used (). Stimuli were presented in a block design over two test runs, each with 10 active task (covert verb generation) and rest (listening to amplitude-modulated white noise) phases. Functional data were acquired using whole brain echo-planar pulse sequence (repetition time =2570 ms, echo time = 50 ms, flip angle = 90°, field of view = 192 × 192, slice thickness = 3 mm, 1 mm interslice gap, slices = 30, matrix size = 64 × 64, voxel size = 3 × 3 ×4 mm3).Analysis was performed in SPM5 (http://www.fil.ion.ucl.ac.uk/spm/software/spm5/). Data processing included coregistration and realignment, spatial normalization and computation of the first-level contrast (verb generation versus rest) after covariation with movement regressors. Using methods described previously (), a region of interest was placed over an extended Broca’s region bilaterally (Brodmann’s areas 44, 45 and 47 and precentral and middle frontal gyri), and threshold independent lateralization indices were calculated for each participant (). Consistent with cut-off values frequently used in language functional MRI studies (; ), participants were grouped into typical (lateralization indices ≥ +0.2) and atypical language lateralization (bilateral: lateralization indices between +0.2 and −0.2; and right lateralized: lateralization indices ≤ −0.2). […]

Pipeline specifications

Software tools MRIcron, SPM
Application Magnetic resonance imaging
Organisms Homo sapiens
Diseases Epilepsy, Epilepsy, Temporal Lobe