Specific Imaging Findings

Tuberous sclerosis complex (TSC) abnormalities of the CNS are cortical tubers, subependymal nodules, and subependymal giant cell astrocytomas (SEGA or SGCA). Cortical tubers are typically randomly scattered focal cortical and subcortical lesions of high T2 signal that are iso- to hypointense on T1-weighted images and primarily affecting supratentorial parenchyma, but may also be found in the cerebellum. They are best depicted on FLAIR images. The tubers generally show bright signal of increased diffusivity on ADC maps and decreased cerebral blood volume on perfusion studies. Calcifications may be present and some enhance with contrast. The white matter may show radial bands of hyperintense T2 signal and cystic degeneration (usually in the deep white matter).

Subependymal nodules are multiple bilateral small (< 12 mm) sharply demarcated masses indenting the contours of the lateral ventricles. They show very low T2 signal, are frequently T1 hyperintense and enhance with gadolinium. A vast majority of subependymal nodules calcify and are hence well seen on CT and T2* MR images, as very bright and very dark nodules, respectively. SEGA are typically located at the subependymal surface of the caudate nucleus near the foramen of Monro. They are slow-growing > 12 mm minimally invasive masses with well-defined margins and avid homogeneous enhancement. Internal calcification and cysts are often present. The adjacent parenchyma is typically preserved unless anaplastic degeneration occurs. Hemimegalencephaly is also found more frequently in patients with TSC.