Abstracts

Rationale: Tuberous sclerosis complex (TSC) is a rare genetic disease affecting multiple organs. About 80-90% of TSC patients develop epilepsy in their lifetime, with the onset typically during the first 12 months of the life, 50-80 % of these patients are medically refractory. Surgical treatment becomes an option for these patients. MEG/MSI (magnetoencephalography / magnetic source imaging) and MR DTI (diffusion tensor imaging) are applied for presurgical evaluation routinely in our center. We reviewed 6 patients who underwent MSI and DTI tractography study, as well as resective surgery in our center. This study is approved by local IRB. Methods: Six TSC patients are included in the study, 3 male, 3 female, age between 2-11 yrs at surgery (Table). MEG was acquired with a 148 channel whole head system (4D neuroimaging, San Diego, CA). The recordings were acquired under sedation with continuous intravenous propofol infusion or propofol induction with precedex continuous infusion. The interictal MEG data were sampled at 508.63 Hz and continuously acquired with an online 1 Hz high pass filter. The data is analyzed with equivalent single dipole model. Cluster of Spikes is defined when at least 5 interictal spikes identified within one centimeter range. DTI was obtained with B=1000 s/mm<+>2<+>, 25 slices, 256*256 matrix, 5 mm slice thickness, 25 spatially isotropically directions. DTI was analyzed with Brainlab (Brainlab AG, Feldkirchen, Germany) iPlan. Seed points include the whole brain, MSI clusters and contralateral symmetrical brain region to generate tracts. The size of the VOIs remain the same (2*2*2 cm3). The fractional anisotropy (FA) threshold is set at 0 to 0.3, minimum length is set between 30mm and 80mm. The DTI images were reviewed by an experienced neuroradiologist. Results: Four out of the 6 TSC patients have one or more MSI clusters identified. These clusters are overlapped with one or two tubers and surrounding tissue. With DTI tractography, there are more fibers adjacent to the tubers identified with MSI (Image). When the minimum length of fiber tracking are modified from 30 mm to 80 mm, the number of fibers going through the epileptogenc tubers becomes identical or less when comparing with the symmetrical region in the opposite hemisphere . Four patients underwent subdural electrode recording, three confirmed the MSI findings, one without cluster identifiied. MSI interictal clusters and ECoG confirmed epileptogenic zones were resected. The outcome listed in Table. Conclusions: MSI plus DTI tractography is useful in pre-surgical evalation for TSC epilepsy surgery. Based on our limited data, for the first time we reported that fibers at the epileptogenic region increased in the TSC patents. These white matter fibers are likely the short ones. Dense white matter tracts might also help us identify the epileptogenic tubers. More research is needed in this population. We thank Mr. Brian Owens and Ms. Carol Hoskin for their technical support.