Transmantle sign-like calcified radial lesion on CT serves as a potential imaging feature for epileptogenic foci in tuberous sclerosis complex: a Case Report

The tuberous sclerosis complex (TSC) is an important cause of drug-resistant epilepsy (DRE) in children. According to international TSC diagnostic criteria, multiple cortical tubers are a key driver of DRE in these patients. Surgical resection of epileptogenic (epi) tubers remains an effective treatment for TSC-related DRE, and precise preoperative identification of these tubers is critical for favorable surgical outcomes. We report the case of a 2-year-old girl with TSC who presented for epilepsy surgery evaluation. She had a 1.5-year history of DRE and was unresponsive to multiple antiepileptic therapies. During preoperative assessment, conventional MRI failed to detect clear cortical tubers. However, CT imaging revealed rare bilateral hyperdense transmantle sign (TMS)-like lesions in central brain regions, which are usually associated with focal cortical dysplasia type IIb (FCD IIb) on MRI. Scalp electroencephalogram (EEG) and stereoelectroencephalogram (SEEG) monitoring confirmed that the seizures originated from the CT calcified radial lesions resembling TMS, which were subsequently resected. Neuropathological examination of the resected tissue revealed balloon cells and dysmorphic neurons, consistent with epi tubers. A 3-year postoperative follow-up confirmed that these CT calcified radial lesions resembling TMS were epi tubers. Notably, only 5%-10% of TSC cases show atypical cortical tubers on MRI and traditionally identified via metabolic abnormalities on magnetic resonance spectroscopy (MRS) or hypometabolic changes on positron emission tomography (PET). To our knowledge, no previous TSC case with atypical cortical tubers on MRI has been reported to exhibit CT calcified radial lesions resembling TMS. This case highlights the clinical value of CT-specific features in identifying epi tubers, especially when cortical tubers are atypical on conventional MRI.