Abstract
Volumetric and morphometric studies have demonstrated structural abnormalities related to chronic epilepsies on a cohort- and population-based level. On a single-patient level, specific patterns of atrophy or cortical reorganization may be widespread and heterogeneous but represent potential targets for further personalized image analysis and surgical therapy. The goal of this study was to compare morphometric data analysis in 37 patients with temporal lobe epilepsies with expert-based image analysis, pre-informed by seizure semiology and ictal scalp EEG. Automated image analysis identified abnormalities exceeding expert-determined structural epileptogenic lesions in 86% of datasets. If EEG lateralization and expert MRI readings were congruent, automated analysis detected abnormalities consistent on a lobar and hemispheric level in 82% of datasets. However, in 25% of patients EEG lateralization and expert readings were inconsistent. Automated analysis localized to the site of resection in 60% of datasets in patients who underwent successful epilepsy surgery. Morphometric abnormalities beyond the mesiotemporal structures contributed to subtype characterisation. We conclude that subject-specific morphometric information is in agreement with expert image analysis and scalp EEG in the majority of cases. However, automated image analysis may provide non-invasive additional information in cases with equivocal radiological and neurophysiological findings.
Highlights
High-resolution T1-weighted magnetic resonance imaging (MRI) is part of todays epilepsy protocol recommendations[1], since they allow readers to identify structural abnormalities associated with temporal lobe epilepsy (TLE)
While some authors demonstrated an additional yield of voxel based morphometry (VBM) for analysis[2,18,19,20,21,22,23,24], others stressed the poor sensitivity and specificity of morphometric grey matter (GM) alterations[7,25]
The feasibility and validity of the proposed framework were evaluated on 47 T1-weighted high-resolution images from 37 patients with mesial temporal lobe epilepsies and hippocampal sclerosis (MTLE-HS) or lateral temporal lobe epilepsies (LTLE)
Summary
High-resolution T1-weighted magnetic resonance imaging (MRI) is part of todays epilepsy protocol recommendations[1], since they allow readers to identify structural abnormalities associated with temporal lobe epilepsy (TLE) Beyond expert rating, these datasets can be further used for computer-assisted quantitative image analysis to generate rater-independent biological fingerprints. Several neuroimaging studies implicate that these abnormalities are not restricted to the hippocampus ipsilateral to seizure onset, but extend along the cingulate cortex, insula, thalamus and frontal lobes, even on the contralateral hemisphere[7,8,9,10,11,12,13,14,15,16,17] While these findings pose a potential role for image-based classification, widespread application on the individual level is hampered by large inter-subject and cohort-dependent variability[7]. Our study assessed the following questions: (1) How frequently are structural abnormalities obscured to visual rating? (2) Do structural abnormalities contribute to lateralization and sublobar determination of the seizure onset zone or of the resection site in individual patients?
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