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Diffusion Tensor Imaging Abnormalities in Focal Cortical Dysplasia

Published online by Cambridge University Press:  02 December 2014

Donald W Gross*
Affiliation:
Division of Neurology, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
Alexandre Bastos
Affiliation:
Centro de Cirurgia de Epilepsia, Hospital Governador Celso Ramos, Florianópolis, SC, Brasil
Christian Beaulieu
Affiliation:
Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada
*
Division of Neurology, Department of Medicine, 2E3.19 Walter C Mackenzie Health Sciences Centre, Edmonton, Alberta, Canada T6G 2B7
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Abstract:

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Purpose:

Focal cortical dysplasia (FCD) is one of the most common underlying pathologic substrates in patients with medically intractable epilepsy. While magnetic resonance imaging (MRI) evidence of FCD is an important predictor of good surgical outcome, conventional MRI is not sensitive enough to detect all lesions. Previous reports of diffusion tensor imaging (DTI) abnormalities in FCD suggest the potential of DTI in the detection of FCD. The purpose of this study was to study subcortical white matter underlying small lesions of FCD using DTI.

Methods:

Five patients with medically intractable epilepsy and FCD were investigated. Diffusion tensor imaging images were acquired (20 contiguous 3mm thick axial slices) with maps of fractional anisotropy (FA), trace apparent diffusion coefficient (trace/3 ADC), and principal eigenvalues (ADC parallel and ADC perpendicular to white matter tracts) being calculated for each slice. Region of interest analysis was used to compare subcortical white matter ipsilateral and contralateral to the lesion.

Results:

Three subjects with FCD associated with underlying white matter hyperintensities on T2 weighted MRI were observed to have increased trace/3 ADC, reduced fractional anisotropy and increased perpendicular water diffusivity which was greater than the relative increase in the parallel diffusivity. No DTI abnormalities were identified in two patients with FCD without white matter hyperintensities on conventional T2-weighted MRI.

Conclusions:

While DTI abnormalities in FCD with obvious white matter involvement are consistent with micro-structural degradation of the underlying subcortical white matter, DTI changes were not identified in FCD lesions with normal appearing white matter.

Résumé:

RÉSUMÉ:But:

La dysplasie corticale focale (DCF) est une des pathologies sous-jacentes les plus fréquentes chez les patients présentant une épilepsie réfractaire au traitement médical. Bien que des manifestations de DCF à l’IRM soient un élément important prédisant un bon résultat chirurgical, l’IRM conventionnelle n’est pas assez sensible pour détecter toutes les lésions. Selon certaines publications, l’imagerie par résonance magnétique du tenseur de diffusion (ITD) pourrait être utile pour la détection de la DCF. Le but de cette étude était d’étudier la substance blanche sous-corticale de petites lésions de DCF au moyen de l’ITD.

Méthodes:

Nous avons évalué cinq patients atteints d’épilepsie réfractaire au traitement médical et de DCF au moyen de l’ITD (vingt coupes axiales contiguës de 3 mm d’épaisseur) avec cartographie de l’anisotropie fractionnaire (AF), du coefficient apparent de diffusion (trace/3 ADC) et calcul des valeurs eigen principales (ADC parallèle et perpendiculaire aux faisceaux de la substance blanche) pour chaque coupe. La substance blanche sous-corticale homolatérale et controlatérale des régions d’intérêt a été comparée.

Résultats:

Chez trois sujets atteints de DCF associée à des zones de substance blanche hyperintenses à l’IRM pondérée en T2 on a observé une augmentation de trace/3 ADC, une diminution de l’AF et une augmentation de la diffusivité aqueuse perpendiculaire qui était plus grande que l’augmentation relative de la diffusivité parallèle. Aucune anomalie ITD n’a été identifiée chez deux patients atteints de DCF sans zones d’hyperintensité au niveau de la substance blanche à l’IRM conventionnelle pondérée en T2.

Conclusions:

Bien que des anomalies de l’ITD chez les patients atteints de DCF ayant une atteinte évidente de la substance blanche soient en faveur d’une altération micro-structurale de la substance blanche sous-corticale sous-jacente, aucun changement n’a été identifié à l’ITD dans les lésions de DCF où la substance blanche semble normale.

Type
Original Article
Copyright
Copyright © The Canadian Journal of Neurological 2005

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