Presentation
Seizures.
Patient Data
At the posterior aspect of the right superior frontal sulcus, is a moderate-sized area of poor grey-white matter differentiation with cortical thickening. FLAIR hyperintensity tapers toward the ventricle is consistent with a transmantle sign.
Conclusion:
Focal cortical dysplasia.
The patient went on to have a resection.
Histology
The sections show cerebral cortex and white matter. Mild gliosis of the sub-pial molecular layer is noted as well as accumulation of corpora amylacea. There is disturbance of laminar architecture. Marked neuronal dystrophy and neuronomegaly is also seen and there are numerous balloon cells some of which are bi-nucleate.
Moderate numbers of neurons are noted in white matter in both specimens. Myelination is normal and there is no evidence of tumor.
Final diagnosis:
The features are of focal cortical dysplasia - Taylor Type IIB. The surgical margins are clear of dysplastic cortex.
A follow-up study obtained following surgical resection demonstrates a generous surgical defect with complete resection of the imaging-defined abnormality.
Case Discussion
When a transmantle sign is identified a fairly confident diagnosis of focal cortical dysplasia can be made on the basis of imaging even when the overlying cortex is subtly involved. More importantly, the transmantle high signal draws your attention to the abnormal cortex which can, otherwise, be difficult to identify.