Cortical tubers without other stigmata of tuberous sclerosis: imaging and pathological findings

There is immense variability in the clinical presentation of tuberous scler osis and many incomplete forms (formes frustes) exist. To investigate the i maging characteristics of cortical tubers seen in tuberous sclerosis unacco mpanied by other stigmata, we reviewed MRI and CT of six patients who met t he criteria for a definitive diagnosis of TS, established solely by the pre sence of a histologically confirmed cortical tuber. Five of the patients ha d a solitary cortical tuber and the last had three lesions, one of which wa s resected and confirmed histologically. The other two lesions were include d in our study. CT showed five tubers as low density, but three were not id entified. No calcified or dense lesions were observed. MRI revealed periphe ral components and inner cores of seven cortical tubers in five patients, w ith differing signal characteristics. The subcortical cores, with T1 and T2 prolongation, were separated from the overlying cortex. Abnormal inhomogen eous high signal was observed in both the cortex and subcortical white matt er on proton-density weighted or FLAIR images. A radially orientated white- matter band was observed in one patient, and central depression of the expa nded gyri in another. In one patient, a cortical tuber was atypical, with a thick cortex on T1-weighted images and a blurred grey/white matter junctio n with diffusely increased signal on T2-weighted images. Cortical tubers wi thout other stigmata of tuberous sclerosis are shown to be distinct from fo cal cortical dysplasia.