Subcortical Alterations in Tissue Microstructure Adjacent to Focal Cortical Dysplasia: Detection at Diffusion-Tensor MR Imaging by Using Magnetoencephalographic Dipole Cluster Localization 1

Department of Diagnostic Imaging, Division of Neurology, Hospital for Sick Children, 555 University Ave, Toronto, ON, Canada.
Radiology (Impact Factor: 6.87). 02/2009; 251(1):206-15. DOI: 10.1148/radiol.2511081092
Source: PubMed


To determine whether changes at diffusion-tensor magnetic resonance (MR) imaging were present in children with intractable epilepsy and focal cortical dysplasia (FCD) in (a) subcortical white matter subjacent to MR imaging-visible areas of FCD, (b) subcortical white matter beyond the MR imaging-visible abnormality but subjacent to a magnetoencephalographic (MEG) dipole cluster, and (c) deep white matter tracts.
The study protocol had institutional research ethics board approval, and written informed consent was obtained. Fifteen children with FCD and intractable epilepsy (mean age, 11.6 years; range, 3.6-18.3 years) underwent diffusion-tensor MR imaging and MEG. Regions of interest were placed in (a) the subcortical white matter subjacent to the MR imaging-visible abnormality, as well as the contralateral side; (b) the subcortical white matter beyond the MR imaging-visible abnormality but subjacent to a MEG dipole cluster, as well as the contralateral side; and (c) deep white matter tracts projecting to or from the MR imaging-visible FCD, as well as the contralateral side. Fractional anisotropy (FA), mean diffusivity, and eigenvalues (lambda(1), lambda(2), lambda(3)) were evaluated.
Eleven of 15 children had MEG dipole clusters, and four children had MEG scatter. There were significant differences in FA, mean diffusivity, lambda(2), and lambda(3) of the subcortical white matter subjacent to the MR imaging-visible FCD (P < .001 for all), as well as that beyond the MR imaging-visible FCD but subjacent to a MEG dipole cluster (P = .001, P = .036, P < .001, and P = .002, respectively), compared with the contralateral side. There were also significant differences in FA (P < .001), mean diffusivity (P = .008), lambda(2) (P < .001), and lambda(3) (P = .001) of the deep white matter tracts projecting to or from the MR imaging-visible FCD compared with the contralateral side.
With use of MEG dipole clusters to localize the epileptogenic zone, diffusion-tensor imaging can help identify alterations in tissue microstructure beyond the MR imaging-visible FCD.

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    • "Quantitative abnormalities of DTI parameters have been reported in WM subjacent to MCD, as well as changes in some tracts in comparison to the contralateral side (Widjaja et al., 2007, 2009). However, the contralateral normal appearing side may not serve as an adequate control for comparisons because structural abnormalities may not be restricted to the ipsilateral hemisphere, as demonstrated with other MRI techniques, such as proton spectroscopy (Leite et al., 2007), nuclear medicine tests and electroencephalography (Iannetti et al., 1996). "
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    ABSTRACT: Purpose Diffusion tensor imaging (DTI) is a magnetic resonance imaging (MRI) technique that can characterize white matter (WM) architecture and microstructure. DTI has demonstrated extensive WM changes in patients with several epileptic syndromes, but few studies have focused on patients with malformations of cortical development (MCD). Our aim was to investigate the quantitative diffusion properties of the corpus callosum (CC), a major commissural bundle critical in inter-hemispheric connectivity, in a large group of patients with MCD. Methods Thirty-two MCD patients and 32 age and sex-matched control subjects were evaluated with DTI at 3.0 T. We analyzed the three major subdivisions of the CC (genu, body, and splenium) with deterministic tractography to yield fractional anisotropy (FA), mean diffusivity (MD), parallel diffusivity (λ||) and perpendicular diffusivity (λ⊥). We further assessed the CC with region of interest (ROI)-based analyses and evaluated different subgroups of MCD (polymicrogyria/schizencephaly, heterotopia, and cortical dysplasia). Partial correlations between diffusion changes and clinical parameters (epilepsy duration and age at disease onset) were also queried. Results There were significant reductions of FA, accompanied by increases in MD and λ⊥ in all segments of the CC in the patients group with both analytical methods. The absolute differences in FA were greater on ROI-analyses. There were no significant differences between the MCD subgroups, and no correlations between clinical parameters of epilepsy and FA. Conclusions Our study indicates DTI abnormalities consistent with microstructural changes in the corpus callosum of MCD patients. The findings support the idea that patients with epilepsy secondary to cortical malformations present widespread WM changes that extend beyond the macroscopic MRI-visible lesions.
    Epilepsy Research 11/2014; 108(9):1533-1542. DOI:10.1016/j.eplepsyres.2014.08.023 · 2.02 Impact Factor
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    • "Interestingly , anatomical alterations in tissue microstructure adjacent to some FCDs were detected using DTI-MR imaging. These overlapped with the localization of clusters of equivalent dipoles of epileptiform spikes (Widjaja et al., 2009). Therefore it is most relevant to determine the functional organization of these epileptogenic networks, since this may give useful indications for a possible surgical intervention and the corresponding prognosis. "
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    ABSTRACT: The main objective of this paper is to examine evidence for the concept that epileptic activity should be envisaged in terms of functional connectivity and dynamics of neuronal networks. Basic concepts regarding structure and dynamics of neuronal networks are briefly described. Particular attention is given to approaches that are derived, or related, to the concept of causality, as formulated by Granger. Linear and non-linear methodologies aiming at characterizing the dynamics of neuronal networks applied to EEG/MEG and combined EEG/fMRI signals in epilepsy are critically reviewed. The relevance of functional dynamical analysis of neuronal networks with respect to clinical queries in focal cortical dysplasias, temporal lobe epilepsies, and "generalized" epilepsies is emphasized. In the light of the concepts of epileptic neuronal networks, and recent experimental findings, the dichotomic classification in focal and generalized epilepsy is re-evaluated. It is proposed that so-called "generalized epilepsies," such as absence seizures, are actually fast spreading epilepsies, the onset of which can be tracked down to particular neuronal networks using appropriate network analysis. Finally new approaches to delineate epileptogenic networks are discussed.
    Frontiers in Neurology 03/2013; 4:8. DOI:10.3389/fneur.2013.00008
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    • "Cortical dysplasia is one of the most common epileptogenic substrates responsible for intractable epilepsy in children, with a nearly 80% incidence in children younger than 3 years of age.10,11 Circumscribed lesionectomy of focal dysplastic lesions provides seizure relief in medically intractable patients with temporal and extratemporal epilepsy.12 "
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    ABSTRACT: Purpose This study was conducted to assess the clinical relevance of diffusion tensor tractography (DTT) in pre- and post-operative evaluations of childhood epilepsy surgery. Materials and Methods Seventy-two patients who received epilepsy surgery between March 2004 and July 2008 were retrospectively analyzed (M : F=40 : 32, ages of 3 months to 24 years, mean age=8.9 years). DTT was performed using a 3.0 T scanner and single-shot spin-echo echo-planar imaging with 32-different diffusion gradient directions. We reviewed the data focusing on the type of surgery, final pathological diagnosis, and how the DTT data were clinically used. Results The most common form of childhood epilepsy surgery was complete resection of an epileptogenic lesion (n=52, 72.2%). The reported etiologies included cortical dysplasia (n=32, 44.4%), hippocampal sclerosis (n=9, 12.5%), brain tumors (n=7, 9.7%), and non-pathologic lesions (n=4, 5.6%) in the final diagnoses. Twenty-one dysplastic cortexes and four brain tumors involved an approximal relationship with the corticospinal tract (n=18), optic radiation (n=2), and arcuate fasciculus (n=5). Additionally, although DTT demonstrated white matter tracts clearly, DTT in the hippocampal sclerosis did not provide any additional information. In cases of callosotomy (n=18, 25%), post-operative DTT was utilized for the evaluation of complete resection in all patients. DTT information was not used in functional hemispherectomy (n=2, 2.8%). Conclusion Preoperatively, DTT was a useful technique in cases of cortical dysplasia and brain tumors, and in cases with callosotomy, postoperatively. DTT should be included among the routine procedures performed in management of epilepsy.
    Yonsei medical journal 01/2013; 54(1):21-7. DOI:10.3349/ymj.2013.54.1.21 · 1.29 Impact Factor
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