Tuberous sclerosis complex (TSC) brain pathology is characterized on MRI by cortical tubers, subependymal nodules, and subependymal giant cell astrocytomas. Seizures, the prominent feature of TSC, are frequently intractable to medical therapy and, in many patients, resection of tubers results in seizure control. However, in approximately 40% of patients, resection of tubers does not control seizures. This fact, as well as evidence from invasive electrophysiological recordings and experimental animal models, suggests that in patients with TSC, there may be extratuberal epileptogenic brain that does not display any apparent abnormality on conventional MRI. The authors hypothesized that high field strength MRI might uncover lesions not seen on conventional MRI in these patients.
Institutional review board approval was obtained to scan 4 patients with TSC (ages 18–26 years) in a 7-T MR unit. Optimized 7-T sequences, including T1- and T2-weighted, FLAIR, SPACE FLAIR, T2*, and MPRAGE studies, were performed. Imaging studies were compared with identical sequences performed using a conventional 1.5-T MR scanner.
In all 4 patients, there was improved visualization of the findings demonstrated on conventional imaging. Importantly, new lesions were detected in all 4 patients, which were not well visualized with conventional MRI. Newly detected lesions included microtubers, radial glial signal abnormalities, subependymal nodules arising from the caudate nucleus, and caudate nucleus lesions.
High field strength MRI detects previously uncharacterized lesions in patients with TSC and allows better detection and delineation of subtle abnormalities. In addition, the data demonstrate a compelling relationship between intraventricular lesions and the caudate nucleus. These data support previous electrophysiological and animal-model findings that demonstrate neurological pathology beyond the conventionally detected lesions in TSC.