Morphometric MRI analysis improves detection of focal cortical dysplasia type II

Abstract

Focal cortical dysplasias type II (FCD II) are highly epileptogenic lesions frequently causing pharmacoresistant epilepsy. Detection of these lesions on MRI is still challenging as FCDs may be very subtle in appearance and might escape conventional visual analysis. Morphometric MRI analysis is a voxel-based post-processing method based on algorithms of the statistical parametric mapping software (SPM5). It creates three dimensional feature maps highlighting brain areas with blurred grey-white matter junction and abnormal gyration, and thereby may help to detect FCD. In this study, we evaluated the potential diagnostic value of morphometric analysis as implemented in a morphometric analysis programme, compared with conventional visual analysis by an experienced neuroradiologist in 91 patients with histologically proven FCD II operated on at the University Hospital of Bonn between 2000 and 2010 (FCD IIa, n = 17; IIb, n = 74). All preoperative MRI scans were evaluated independently (i) based on conventional visual analysis by an experienced neuroradiologist and (ii) using morphometric analysis. Both evaluators had the same clinical information (electroencephalography and semiology), but were blinded to each other's results. The detection rate of FCD using morphometric analysis was superior to conventional visual analysis in the FCD IIa subgroup (82% versus 65%), while no difference was found in the FCD IIb subgroup (92% versus 91%). However, the combination of conventional visual analysis and morphometric analysis provided complementary information and detected 89 out of all 91 FCDs (98%). The combination was significantly superior to conventional visual analysis alone in both subgroups resulting in a higher diagnostic sensitivity (94% versus 65%, P = 0.031 for FCD IIa; 99% versus 91%, P = 0.016 for FCD IIb). In conclusion, the additional application of morphometric MRI analysis increases the diagnostic sensitivity for FCD II in comparison with conventional visual analysis alone. Since detection of FCDs on MRI during the presurgical evaluation markedly improves the chance of becoming seizure free postoperatively, we apply morphometric analysis in all patients who are MRI-negative after conventional visual analysis at our centre.

Linking MRI post-processing with Magnetic source imaging in MRI-negative epilepsy

“…FCD has been demonstrated as the most common pathology underlying MR-epilepsies, 48 and among common imaging characteristics of FCD, gray-white matter junction blurring occurs most frequently. 33,49 Consistent with the published literature, 30,32 we found the gray-white junction file to be the most helpful feature map. Others have reported that the extension file by itself can also uniquely identify some subtle lesions, 32 but our analysis of this cohort did not support this observation.…”

“…[23][24][25][26][27][28][29] Among them, a voxel-based MRI morphometric analysis program (MAP), implemented using parametric mapping software (SPM), has been used to detect subtle cortical malformations with a high degree of sensitivity. [30][31][32] In practice, MAP directs the reader's attention to suspicious brain regions, on the basis of abnormal gray-white junction blurring, abnormal cortical gyration, or abnormal cortical thickness. These features, particularly the blurred gray-white matter junction, are common accompaniments of FCD.…”

Optimizing MR Imaging Detection of Type 2 Focal Cortical Dysplasia: Best Criteria for Clinical Practice

“…In addition, positive MR imaging findings (59% of our patients) were based on conventional visual analysis. Voxel-based postprocessing methods proved a significant benefit in comparison with visual analysis alone 33,34 and would possibly decrease our rate of negative MR imaging findings. However, these techniques apply algorithms not applicable in routine practice.…”

The influence of lesion volume, perilesion resection volume, and completeness of resection on seizure outcome after resective epilepsy surgery for cortical dysplasia in children

“…Methods for the automated detection of areas of FCDs on imaging using automated segmentation and postacquisition image-processing algorithms aimed at detecting cortical thickness or gray matter-white matter junction blurring are being developed and, in some situations, are superior to expert human visual analysis. 27 The influence of the 3-T versus the 1.5-T scanner on the detection of the lesion or the resection to lesion volume ratios were not specifically analyzed in our study. However, other studies have shown that the use of 3-T MRI in patients suspected of having a Type 2 FCD improves the detection rate and the lesion characterization because of the transmantle sign being more clearly visible at 3 T. 17 Other novel techniques include the use of optical coherence tomography and the use of high-frequency ultrasonography for micrometer-level intraoperative resolution and the delineation of these lesions.…”