Abstracts

Rationale: TSC is an autosomal dominant disease characterized by the growth of tumors in multiple organ systems including the brain, skin, lung, and kidney. The majority of the children with TSC develop refractory epilepsy early in their development. There are limited studies investigating the impact of subclinical seizures in children with TSC on epilepsy surgery outcome and development. The purpose of our study is to describe the relationship of subclinical seizures detected by stereoelectroencephalography (sEEG) to developmental status and post-operative seizure freedom in children with TSC who underwent epilepsy surgery. Methods: This is a retrospective single center outcome study. All encounters under Texas Children's Hospital with patients with TSC who had undergone sEEG prior to or after stereotactic MRI-guided laser ablation were reviewed. Patient demographics, medical and surgical history including development, details of sEEG and ablations, and Engel score outcomes at 6 months were reviewed. Associations between the presence of subclinical seizures on sEEG and surgical outcome as well as pre-operative developmental diagnoses were assessed. Results: Twenty-three pediatric patients with TSC-related epilepsy (Male:Female = 13:10, Age range: 23 months - 17 years, Seizure onset age range: 3 days - 23 months) underwent Phase II evaluation with sEEG (Number of depth electrode range: 4 - 7). Twenty-six MRI-guided stereotactic laser ablations were performed on 22 patients. (One patient did not have a surgery due to low likelihood for palliative benefit. One patient had two surgeries separated by 33 months. Three patients had two surgeries each within the same month.)On sEEG prior to ablation, subclinical seizures were detected in 18 of 23 (78.3%) patients. Within the eight patients who had high concordance between clinical and subclinical seizures, four (50%) had Engel surgical outcome category I or II. Within the nine patients who did not had high concordance between clinical and subclinical seizures, two (22.2%) had Engel surgical outcome category I or II. (P = 0.25)Four patients did not have subclinical seizures prior to the ablations. While not all patients underwent post-ablation monitoring, three additional patients had no subclinical seizures detected on sEEG after the ablations. Within these seven patients, three (42.9%) had Engel surgical outcome category I or II. Within the other 16 patients, five (31.3%) had Engel surgical outcome category I or II. (P = 0.59)There were three patients who did not have subclinical seizures with no history of prior surgery. All three had developmental delay or intellectual disability, although only one of them was diagnosed with autism. Within the other 20 patients who either had prior surgery or subclinical seizures on sEEG, 19 (95%) had developmental delay and nine (45%) had autism. Conclusions: Subclinical seizures are prevalent in children with TSC and may be reflective of a higher disease burden. A high concordance between clinical and subclinical seizures may be predictive for a favorable surgical outcome at 6 months. In addition, the absence of subclinical seizures on sEEG may be predictive for a favorable surgical outcome at 6 months. These results were limited by the sample size to provide adequate power. Further study with a larger population is warranted. Funding: No funding