MRI-Based Lesion Profiling of Epileptogenic Cortical Malformations
Focal cortical dysplasia (FCD), a malformation of cortical development, is a frequent cause of drug-resistant epilepsy. This lesion is histologically classified into Type-IIA (dyslamination, dysmorphic neurons) and Type-IIB (dyslamination, dysmorphic neur
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Abstract. Focal cortical dysplasia (FCD), a malformation of cortical development, is a frequent cause of drug-resistant epilepsy. This lesion is histologically classified into Type-IIA (dyslamination, dysmorphic neurons) and Type-IIB (dyslamination, dysmorphic neurons, and balloon cells). Reliable in-vivo identification of lesional subtypes is important for preoperative decision-making and surgical prognostics. We propose a novel multi-modal MRI lesion profiling based on multiple surfaces that systematically sample intra- and subcortical tissue. We applied this framework to histologically-verified FCD. We aggregated features describing morphology, intensity, microstructure, and function from T1-weighted, FLAIR, diffusion, and resting-state functional MRI. We observed alterations across multiple features in FCD Type-IIB, while anomalies in IIA were subtle and mainly restricted to FLAIR intensity and regional functional homogeneity. Anomalies in Type-IIB were seen across all intra- and subcortical levels, whereas those in Type-IIA clustered at the cortico-subcortical interface. A supervised classifier predicted the FCD subtype with 91% accuracy, validating our profiling framework at the individual level. Keywords: Intracortical, FCD, Multimodal MRI, Histopathological prediction.
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Introduction
Focal cortical dysplasia (FCD), a highly epileptogenic malformation of cortical development, is a frequent cause of drug-resistant epilepsy in children and adults. Surgical resection of these lesions is the only effective treatment to arrest the seizures. Histologically, FCD is characterized by cortical dyslamination associated with various intra-cortical cytological anomalies: large dysmorphic neurons typify FCD TypeIIA, while clusters of balloon cells and dysmorphic neurons are characteristic of Type-IIB [1]. In addition to cortical abnormalities, neuronal density is increased in the white matter immediately below the cortical interface. Radiological assessments suggest that these histological subtypes may have diverging morphological and intensity signatures, with Type-IIA being generally more subtle than IIB [1]. Moreover, difficulties to discern lesional boundaries from the surrounding normal cortex, together
© Springer International Publishing Switzerland 2015 N. Navab et al. (Eds.): MICCAI 2015, Part II, LNCS 9350, pp. 501–509, 2015. DOI: 10.1007/978-3-319-24571-3_60
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with a more extended epileptogenic network [2], explain less favorable surgical outcome prospects in FCD Type-IIA compared to type-IIB [3]. Given the irreversible nature of surgery, it is important to predict FCD subtypes in vivo. We propose a surface-based multivariate MRI framework that jointly assesses morphology, intensity, diffusion, and functional characteristics, taking advantage of their covariance for improved lesion profiling. To model FCD-related cortical dyslamination and white matter gliosis, we sampled imaging parameters on multiple surfaces at various cortical and subcortical depths. We used a supervised classifie
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