Morphometric MRI analysis enhances visualization of cortical tubers in tuberous sclerosis

Focal cortical dysplasias (FCD) type IIb and cortical tubers in tuberous sclerosis complex (TSC) are histopathologically similar and are both epileptogenic lesions frequently causing pharmacoresistant epilepsies. Morphometric analysis of T1- and T2-weighted MRI volume data sets can enhance visualization of FCD. Here, we retrospectively investigated whether morphometric MRI analysis is of equal benefit for visualizing cortical tubers.

Morphometric analysis was applied to T1- and partly also T2-weighted 1.5T or 3T MRI volume data sets of 15 TSC patients using a fully automated MATLAB(®) script (i.e. MAP07) commonly used for FCD detection. In this study, focus was on the most sensitive of the resulting morphometric feature maps (i.e. the 'junction image') which highlights blurring of the gray-white matter junction in comparison to a normal database. The visualization of tubers in these 'junction images' was quantitatively compared with that in conventional MR sequences.

In all patients, morphometric analysis visualized almost all tubers detected in the normal MRI, and additionally highlighted on average 23% (range 3-50%) more tubers which were not detected by visual analysis of the conventional MR sequences. When T2 volume data sets from a 3T scanner were available for postprocessing, the rate of additionally detected tubers increased to 29% on average. These formerly overlooked tubers were usually smaller than the tubers already found in the conventional MRI.

Morphometric analysis of MRIs in TSC can highlight cortical tubers which are likely to be overlooked in conventional MRI sequences alone. Additionally detected tubers may be of potential importance for both presurgical evaluation and initial diagnosis of TSC.