Localization of the Epileptogenic Foci in Tuberous Sclerosis Complex: A Pediatric Case Report

Abstract

Tuberous sclerosis complex (TSC) is a rare disorder of tissue growth and differentiation, characterized by benign hamartomas in the brain and other organs. Up to 90% of TSC patients develop epilepsy and 50% become medically intractable requiring resective surgery. The surgical outcome of TSC patients depends on the accurate identification of the epileptogenic zone consisting of tubers and the surrounding epileptogenic tissue. There is conflicting evidence whether the epileptogenic zone is in the tuber itself or in abnormally developed surrounding cortex. Here, we report the localization of the epileptiform activity among the many cortical tubers in a 4-year-old patient with TSC-related refractory epilepsy undergoing magnetoencephalography (MEG), electroencephalography (EEG), and diffusion tensor imaging (DTI). For MEG, we used a prototype system that offers higher spatial resolution and sensitivity compared to the conventional adult systems. The generators of interictal activity were localized using both EEG and MEG with equivalent current dipole (ECD) and minimum norm estimation (MNE) methods according to the current clinical standards. For DTI, we calculated four diffusion scalar parameters for the fibers passing through four ROIs defined: (i) at a large cortical tuber identified at the right quadrant, (ii) at the normal appearing tissue contralateral to the tuber, (iii) at the cluster formed by ECDs fitted at the peak of interictal spikes, and (iv) at the normal appearing tissue contralateral to the cluster. ECDs were consistently clustered at the vicinity of the large calcified cortical tuber. MNE and ECDs indicated epileptiform activity in the same areas. DTI analysis showed differences between the scalar values of the tracks passing through the tuber and the ECD cluster. In this illustrative case, we provide evidence from different neuroimaging modalities, which support the view that epileptiform activity may derive from abnormally developed tissue surrounding the tuber rather than the tuber itself.

Interictal High Frequency Oscillations Detected with Simultaneous Magnetoencephalography and Electroencephalography as Biomarker of Pediatric Epilepsy

“…For both patients, HFOs were localized concordant for scalp EEG and MEG (see Figure 5). Localization differences of few mm may be attributed to the superior localization ability of high-density MEG compared to scalp EEG 70 , or may represent different underlying generators 71 . The localization was also concordant with the irritative zone as this was defined by MEG (see Figure 5 -right panel).…”

Resting‐State fMRI Networks in Children with Tuberous Sclerosis Complex

“…TSC presents with benign hamartomas in multiple organs including the brain . Cortical tubers are considered the hallmark lesions of TSC in the central nervous system; however, no consistent relationship has been shown between the number and location of cortical tubers and autistic symptoms or seizures …”

Upper limb revascularization with reversed vein graft and microvascular anastomoses after brachial artery aneurysm resection in a child with tuberous sclerosis

“…It may occur sporadically or on a familial basis with autosomal dominant inheritance. Patients develop benign hamartomas in the brain and other organs 3 . Neurological presentation may involve seizures (more than 90% of cases) and progressive psychomotor retardation (more than 50% of cases).…”