MRI Abnormalities Predominate in the Bottom Part of the Sulcus with Type II Focal Cortical Dysplasia: A Quantitative Study

Abstract

BACKGROUND AND PURPOSE: Type II focal cortical dysplasia is a common histopathological substrate in focal epilepsy. This study explored the spatial distribution of abnormal findings on MR imaging across the sulcus with type II focal cortical dysplasia using quantitative MR imaging postprocessing techniques. MATERIALS AND METHODS: The morphometric analysis program and normalized FLAIR signal intensity analysis were applied to retrospectively analyze the MR imaging data of 58 patients with histopathologically confirmed type II focal cortical dysplasia. We divided the dysplastic sulcus into the bottom and nonbottom parts. Then spatial distribution types 1, 2, and 3 were arbitrarily defined as the abnormal findings on MR imaging (z-value Ͼ threshold) located in the bottom part, both the bottom and nonbottom parts, and the nonbottom part, respectively. For type 2, the mean z-values and standardized volumes of abnormal findings on MR imaging were compared between the bottom and nonbottom parts. RESULTS: Abnormal findings on MR imaging were detected by quantitative techniques in 42 of 58 enrolled patients. Among these 42 patients, 38 and 26 patients showed gray-white matter junction blurring and cortical FLAIR hyperintensity, respectively, which were the 2 most common abnormal MR imaging features. Gray-white matter junction blurring manifested as types 1, 2, and 3 in 24, 13, and 1 patient, respectively, and the corresponding counts for cortical FLAIR hyperintensity were 12, 13, and 1 patient. For the 2 most common abnormal findings on MR imaging spatially manifested as type 2, higher mean z-values and larger corresponding standardized volumes of abnormalities were found in the bottom part. CONCLUSIONS: Abnormal findings on MR imaging predominate in the bottom part of the sulcus with type II focal cortical dysplasia, which indicates that this malformation is bottom-of-sulcus-rooted. ABBREVIATIONS: FCD ϭ focal cortical dysplasia; MAP ϭ morphometric analysis program; nFSI ϭ normalized FLAIR signal intensity

Bottom-of-sulcus dysplasia: the role of 18F-FDG PET in identifying a focal surgically remedial epileptic lesion

“…This was in line with a previous study in an overlapping BOSD cohort (Harvey et al 2015), as well as in other FCD cohorts with type II pathology (Chassoux et al 2010). In previous FCD studies, the primary predictor of unfavourable surgical outcome is reported to be incomplete removal of the dysplastic lesion (Kim et al 2009;Krsek et al 2009;Rowland et al 2012). Accurately identifying and removing the dysplastic lesion is thus of crucial importance.…”

“…Initial review of MR images missed the dysplastic lesion in 20% of cases, while coregistration with PET enabled detection of the BOSD in all cases. The relatively high sensitivity of MRI to detect BOSD lesions in our cohort may relate to improved detection with 3 T MRI and better acquisition methods when compared to previous studies in which negative MRIs have been commonly reported (Salamon et al 2008;Chassoux et al 2010). Nonetheless, 18 F-FDG PET was more sensitive than MRI in detecting hypometabolic abnormalities consistent with the dysplastic lesion, at least upon initial review, detecting an abnormality in 95% of cases.…”

“…4). Indeed, others similarly report the high localising value of 18 F-FDG PET following PET/MRI coregistration in FCD, particularly in cases where MRI alone was negative or doubtful (Salamon et al 2008;Chassoux et al 2010;Desarnaud et al 2018). The inclusion of PET in presurgical workup is indeed valuable in localising these small BOSD lesions, in line with findings from FCD cohorts.…”

“…Another limitation to our work relates to the PET analysis, which in this study was limited to visual assessments, given its integration into routine pre-surgical workup. There are various quantitative techniques, including post-processing methods and machine-learning approaches, that have recently exhibited improved detection of FCD lesions (Tan et al 2018 ; Liu et al 2019 ) and improved detection of BOSD (Besson et al 2008 ). Future work could benefit from investigating quantitative methods, particularly those combining MRI and PET, in the detection and associated surgical outcomes in BOSD.…”

Surgical Treatments for Epilepsy

“…22 Careful evaluation of the MRI by an expert neuroradiologist provides additional sensitivity, with identification of lesions such as depth-of-the-sulcus dysplasia or periventricular nodular heterotopias. 23 Comprehensive neuropsychological testing is necessary both to localize preoperative deficits that may correlate with the seizure-onset zone and to a In some patients who receive intracranial evaluation, the epileptogenic zone is not fully delineated (ie, the seizure-onset zone is not captured), and subsequent invasive evaluation is necessary before offering surgical therapy. b Corpus callosotomy may be considered to reduce the frequency and severity of drop seizures, which include generalized tonic-clonic, tonic, and atonic seizures.…”