Prenatal magnetic resonance imaging findings of tuberous sclerosis complex in fetuses

This study aimed to characterize the prenatal imaging features of brain and cardiac lesions associated with tuberous sclerosis complex (TSC), with particular focus on fetal magnetic resonance imaging (MRI) findings, and to explore the complementary role of fetal MRI, fetal echocardiography, and genetic testing in prenatal evaluation.

This retrospective study analyzed prenatal neurocardiac MRI findings in fetuses diagnosed with TSC or cardiac rhabdomyomas through genetic and/or clinical assessment between 2018 and 2025.

Twenty-four fetuses with TSC were included, 23 underwent fetal brain MRI, which revealed abnormalities in 15 cases, including subependymal nodules, cortical dysplasias, and subependymal giant cell astrocytoma. Subependymal nodules appear as hypointense on T2-weighted imaging (T2WI) (14/14, 100%), and the vast majority appear as hyperintense on T1-weighted imaging (T1WI) (12/14, 85.7%), while most show hyperintensity on diffusion-weighted imaging (DWI) (11/14, 78.6%). Cortical dysplasia included cortical tubers and white matter migrational abnormalities. Cortical dysplasia shows hyperintensity on T1WI in all cases (8/8, 100%), hypointensity on T2WI (6/8, 75%), and predominantly hyperintensity on DWI (6/8, 75%). Subependymal giant cell astrocytoma appears hypointense on T2WI and hyperintense on T1WI. According to our research, T1WI was superior to T2WI in demonstrating cortical dysplasia. Intracranial lesions in tuberous sclerosis complex manifest as hyperintense on T1WI (contrasting with the dark background of white matter), a phenomenon often referred to as the "bright spot" sign. Cardiac MRI was performed in 12 of the 24 fetuses. Cardiac rhabdomyomas appear as hyperintense signals on T2WI against the dark background of the myocardium (12/12, 100%), a finding commonly referred to as the "bright spot" sign.

The "bright spot" sign on MRI has significant diagnostic value for fetal TSC, particularly for identifying cortical dysplasia and cardiac rhabdomyoma. In cases of suspected TSC or cardiac rhabdomyoma, combining prenatal ultrasound with MRI enhances diagnostic accuracy, facilitating better clinical management.