Radiologic and Pathologic Features of the Transmantle Sign in Focal Cortical Dysplasia: The T1 Signal Is Useful for Differentiating Subtypes

Abstract

BACKGROUND AND PURPOSE: The transmantle sign is a characteristic MR imaging finding often seen in focal cortical dysplasia type IIb. The transmantle sign is typically hyperintense on T2WI and FLAIR and hypointense on T1WI. However, in some cases, it shows T1 high signal. We evaluated the imaging and pathologic findings to identify the causes of the T1 high signal in the transmantle sign. MATERIALS AND METHODS: We retrospectively reviewed the preoperative imaging data of 141 consecutive patients with histologically proved focal cortical dysplasia. We selected 25 patients with focal cortical dysplasia with the transmantle sign and divided them into groups based on the pathologic focal cortical dysplasia subtype and T1 signal of the transmantle sign. We evaluated the clinical, radiologic, and pathologic findings, including the number of balloon cells and dysmorphic neurons and the severity of gliosis or calcifications and compared them among the groups. RESULTS: Nine of the 25 patients had a T1-high-signal transmantle sign; the other 16 patients did not. All 9 patients with a T1-high-signal transmantle sign were diagnosed as type IIb (group A). Of the 16 patients with no T1-high-signal transmantle sign, 13 were diagnosed as having type IIb (group B), and the other 3 patients, as type IIa (group C). The number of balloon cells was significantly higher in group A than in the other groups, but there were no differences regarding dysmorphic neurons, the severity of gliosis, or calcifications. CONCLUSIONS: Approximately 6% (9/141) of this patient series had a T1-high-signal transmantle sign, and all were type IIb. The signal may reflect a rich density of balloon cells. This finding could support the differentiation of subtypes, especially type IIb.

MR Imaging Detection of CNS Lesions in Tuberous Sclerosis Complex: The Usefulness of T1WI with Chemical Shift Selective Images

“…Kimura et al 18 reported that T1 hyperintensity of the transmantle sign of FCD type IIb is associated with the high density of balloon cells, independent of the density of dysmorphic neurons, the severity of gliosis, and calcifications. In a study by Kusama et al, 19 T1WI-CHESS detected the transmantle sign of FCD type IIb as marked hyperintensity where numerous balloon cells were located in a resected specimen.…”

“…However, our present findings were consistent with the radiology-pathology correlation in FCD type IIb. 18 Further radiology-pathology correlation studies are also needed for TSC. A third limitation is that the ages of the patients varied, including patients whose myelination is ongoing and those with completed myelination.…”

“…[15][16][17] Earlier research demonstrated that a T1WI high-signal area of the WM lesions of FCD type IIb was correlated with the cellularity of balloon cells, independent of calcifications. 18 Another case report also observed that T1WI with chemical shift selective (T1WI-CHESS) imaging, which is the most frequently used technique for the fat-suppression pulse, could clearly visualize the T1WI high-signal area in FCD type IIb because of its background signal suppression due to the magnetization transfer effect and the fat suppression of normal WM, which contains fat-rich myelin. 19 Moreover, the superiority of T1WI-CHESS compared with T1WI-MTC was reported for neuromelanin imaging.…”

Prognostic analysis in children with focal cortical dysplasia II undergoing epilepsy surgery: Clinical and radiological factors

“…The detailed qualitative MRI indicators were as follows: cortex thickening, gray-white matter blurring, transmantle sign, and signal intensity changes of both the gray and white matter. The definition of the transmantle sign was “a markedly hyperintense funnel-shaped subcortical zone tapering toward the lateral ventricle” ( 15 ). The MRI-negative was defined as the invisible abnormal signals of the cortical or subcortical part.…”

Imaging the Patient with Epilepsy

“…More recently a study by Kumura et al revealed that T1-weighted hyperintense transmantle sign is associated with higher density of balloon cells without significant differences in the number of dysmorphic neurons or the severity of gliosis ( Fig. 10.9) [16]. Identifying a T1 hyperintense transmantle sign may have clinical relevance.…”