MR Imaging Findings of Cortical Dysplasia of the Brain: Correlation with Pathologic Grades and Subtypes

ABSTRACT

PURPOSE: Cortical dysplasia is known to be of variety of MR imaging findings. We attempted to classify MR imaging findings of cortical dysplasia into several types and to correlate those with histopathologic grades and subtypes. MATERIALS AND METHODS: Preoperative MR images of 97 patients with pathologically-proven cortical dysplasia were retrospectively reviewed with knowledge of the diagnosis and operative sites. The patients were divided into MR- positive and MR-negative groups based on the presence or absence of MR imaging abnormalities. In MR-positive group, MR imaging features were arbitrarily classified into four types (atrophic, cortical-band, inward-rounding, and nonspecific types) on the basis of size of the gyrus and adjacent CSF space, cortical thickness, signal intensity of the subcortical white matter, and blurring of the gray-white matter junction. The pathologic findings were also retrospectively reviewed without knowledge of MR imaging findings and divided into three grades (mild, moderate, and severe) and two subtypes (nonballoon-cell and balloon-cell). Pathologic grades and subtypes were compared between MR-positive and MR-negative groups. Four MR types of the MR-positive group were correlated with the pathologic grades and subtypes. RESULTS: MR-positive and MR-negative groups consisted of 39 (40%) and 58 (60%) patients, respectively . Of the MR-positive group, atrophic type was seen in 13 patients (33%), corticalband type in 9 (23%), inward-rounding type in 9 (23%), and nonspecific type in 8 (21%). There was no significant difference in the pathologic grades between MR-positive and MR-negative groups, although MR-positive group tended to have higher pathologic grades than MR-negative group did. Balloon-cell subtype was found significantly higher in MR-positive group than in MRnegative group (p<0.05) 21% (8/39) versus 5% (3/58). The inward-rounding type corresponded to the pathologically severe grade and balloon-cell subtype in 78% (7/9) and 56% (5/9) of the patients, respectively, while the atrophic type to the mild grade and nonballoon-cell subtype in 77% (10/13) and 100% (13/13), respectively. CONCLUSION: A variety of MR imaging abnormalities were found in 40% of the patients with cortical dysplasia and those were classified into four types (atrophic, cortical-band, inwardrounding, and nonspecific types), of which the inward-rounding type correlated well with the pathologically severe grade and balloon-cell subtype, whereas the atrophic type with the mild grade and nonballoon-cell subtype.