Subcortical alterations in tissue microstructure adjacent to focal cortical dysplasia: detection at diffusion-tensor MR imaging by using magnetoencephalographic dipole cluster localization.
OBJECTIVE
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Widjaja
Elysa
E
Department of Diagnostic Imaging, Division of Neurology, Hospital for Sick Children, 555 University Ave, Toronto, ON, Canada. Elysa.Widjaja@sickkids.ca
Zarei Mahmoodabadi
Sina
S
Otsubo
Hiroshi
H
Snead
O Carter
OC
Holowka
Stephanie
S
Bells
Sonya
S
Raybaud
Charles
C
D000293:Adolescent; D000465:Algorithms; D001921:Brain / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D054220:Malformations of Cortical Development / Q000473:pathology*; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity