Voxel‐based Morphometry Reveals Excess Gray Matter Concentration in Patients with Focal Cortical Dysplasia

Abstract

Summary:Purpose: Many patients with focal cortical dysplasia (FCD) continue to have seizures after surgical treatment. The usual explanation for the poor surgical outcome is the presence of residual dysplastic tissue missed by the preoperative neuroimaging investigation and therefore not resected during surgery. We apply a voxel-based morphometry (VBM) analysis to the magnetic resonance imaging (MRI) scans from patients with epilepsy and visually detected FCD to investigate whether (a) VBM is able to detect gray-matter concentration (GMC) abnormalities in patients with FCD, and (b) whether the extent of GMC abnormalities in the brain of these patients differs from the regions observed by using visual inspection.Methods: We studied 11 patients with visually detected FCD (eight of them with histologic confirmation of FCD). The GMC from each one of these patients was compared with the mean GMC from a control group of 96 normal healthy subjects by using an optimized VBM protocol.Results: Ten of 11 patients showed statistically significant GMC excess, and among patients with GMC excess, only one showed GMC excess that was not exactly correspondent to the visually detected FCD. Seven patients exhibited excess in GMC extending beyond the area of visually detected FCD.Conclusions: This preliminary neuroimaging study suggests that (a) VBM can detect GMC excess in patients with FCD, and (b) GMC excess in these patients can extend to brain areas not visually defined as abnormal. Abnormal areas detected by VBM can possibly correspond to mild malformations of cortical development, supporting the notion that the surgical refractoriness observed in patients with FCD can be due to the incomplete resection of the dysplastic tissue.

Whole-brain MRI phenotyping in dysplasia-related frontal lobe epilepsy

“…6,7 In this study, we aimed to compare whole-brain morphology between frontal lobe epilepsy cohorts with histologically verified FCD type I and II. Our approach was motivated by case reports indicating that FCD type II may present with histologic 8 and MRI anomalies 9,10 in remote cortices resembling those found in the primary lesion and that type I may be associated with subtle multilobar hypoplasia on MRI. 11 We hypothesized widespread, yet diverging patterns of anomalies, with cortical thinning in FCD type I and thickening in type II.…”

MRI-Based Correction for Partial-Volume Effect Improves Detectability of Intractable Epileptogenic Foci on 123I-Iomazenil Brain SPECT Images

“…This finding implies an increase in the volume of the gray matter or decrease in the volume of the adjacent white matter in the lesion areas, compared with that in the corresponding contralateral normal areas. In the previous study (27), an increase in the regional gray matter concentration in malformations of cortical development in patients with focal cortical dysplasia was detected by voxel-based morphometry. In addition, the local increase of the gray matter volume has been reported to coincide with that of the white matter volume, as detected by voxel-based morphometry, around pathologic sclerotic medial temporal lesions in cases of temporal lobe epilepsy (28).…”

MR Imaging–Based Correction for Partial Volume Effect Improves Detectability of Intractable Epileptogenic Foci on Iodine 123 Iomazenil Brain SPECT Images: An Extended Study with a Larger Sample Size

“…7 In cases of MCD, decrease in inhibitory synaptic connectivity 15 or altered transcription of genes encoding GABAergic receptors 16 has been reported. In a previous study, 17 on the other hand, increase in the regional gray matter concentration in MCD was detected in patients with focal cortical dysplasia by voxel-based morphometry. 18 The case of subcortical heterotopia indicated in Fig 3C is thought to be a representative example.…”