Abstracts

Rationale: Transcranial high-intensity focused ultrasound surgery (FUS) is capable of conformal target thermoablation without passing instruments through the brain. FUS recently received FDA approval for creation of a thalamotomy to treat refractory tremor. Under an Investigational Device Exemption (IDE no. G160189), we have launched a pilot study aimed at treating pediatric brain tumors with FUS (ClinicalTrials.gov: NCT03028246). Methods: A 21 year old female with a history of gelastic seizures had previously undergone a transventricular endoscopic resection of a Type IIIA hypothalamic hamartoma. She was initially seizure free for two years, but then relapsed. T2-weighted MR imaging revealed a small remnant of tumor along the left parahypothalamic wall. Using the InSightec ExAblate 4000 FUS system we targeted the tumor and its vertical gliotic attachment plane immediately adjacent to the hypothalamus. The procedure was done under general anesthesia in a GE 3T MR scanner. Tumor ablation to 59°C was monitored with phase MR thermography and confirmed with post-operative diffusion-weighted imaging. Results: Complete tumor ablation was achieved. The patient spent one night in the hospital and was discharged to home the following day on a rapid steroid taper. She returned to school that same week. No appetite, endocrine, cognitive or motor complications occurred. At the three month time point, she remained seizure free and will be followed with serial imaging and clinical visits for a minimum of one year. Conclusions: This is the first case of subcortical epilepsy treated with FUS and the first of ten cases to be treated with FUS under our IDE focusing on pediatric brain tumors. Proof-of-concept that incisionless transcranial thermoablation of tumors and elliptic foci is possible will be used to motivate a multicenter pivotal trial of transcranial FUS in the pediatric population. Funding: The Focused Ultrasound Foundation of Virginia generously provided funding for this feasibility safety trial (Grant No. FUS530). InSightec is our FDA regulatory sponsor but we have not requested any commercial financial support for this study.