1158 Medically Refractory Epilepsy in Tuberous Sclerosis Necessitating Surgery: Electrophysiological, Morphological, and Spatial Assessment of Tubers Demonstrates Neurofilament Deposition in Epileptogenic Foci

INTRODUCTION: Tuberous Sclerosis Complex(TSC) causes benign tubers and are associated with medically intractable epilepsy. Most epilepsies are multicentric, however patients may qualify for surgery if primary epileptogenic tubers can be pinpointed. METHODS: A prospective database documented epilepsy patients since establishing our center of excellence from 2019–2023 with at least 1 year follow up. en-bloc resections of three tubers were oxygenated in aCSF, sectioned, cultured with neuroprotective media, transduced with GFP-fluorescent EF1-A/Syn-1/GCaMP6. Patch-clamping, Multielectrode Array, Immunofluorescence(I.F.) were used. I.F., Transmission Electron Microscopy(TEM), and single nuclear RNA sequencing compared tuber core, edge, and surrounding parenchyma. RESULTS: Of 107 patients with lesional epilepsy undergoing surgery, six(5.6%) were diagnosed with TSC. While 62%(n = 63) of lesional patients achieved seizure freedom, only two TSC patients(33%) were seizure free(P = 0.156). Further tissue analysis via lTEM demonstrated dysregulated mitochondria in TSC versus control. I.F. showed Neurofilament light-chain(NfL) upregulation in tubers, decreasing at the border, and even further outside of tubers(P < 0.05) although this region still contained higher NfL versus control(P < 0.001). Brain slice TSC-GFP+ neurons demonstrated significant enlargement of somas/dendritic spines versus control(P < .005). Patch-clamping showed increased firing frequency, resting membrane potential, and AP amplitude compared to control(P < 0.05). TSC neurons failed to return to resting membrane potential, further enhancing neuronal network activity. gCAMP6-TSC neurons demonstrated increased AP frequency(P < 0.05) which was decreased with Rapamycin(P < 0.05). CONCLUSIONS: This series of TSC patients undergoing surgery demonstrates a reasonable response rate to surgical intervention, while our novel brain slice assay/spatial analysis of TSC tubers has for the first time demonstrated ex-vivo electrophysiological/morphological characteristics of TSC neurons, serving as a foundation for understanding --cellular changes of this disease, and opening avenues for therapeutic intervention.