Feasibility and safety of MR-guided focused ultrasound lesioning in the setting of deep brain stimulation

Background: Patients treated with deep brain stimulation (DBS) often develop symptom progression. If safe, focused ultrasound (FUS) lesioning could be used for patients unable to undergo further DBS surgery. Objective: To test the feasibility and safety of MR-guided FUS surgery in the setting of a previously implanted DBS system. Methods: Three preclinical experiments were designed to test feasibility and safety. Hydrogels were implanted with an electrode, and FUS lesions were targeted adjacently. Cadavers were implanted with a thalamic electrode, and FUS lesions were targeted in the contralateral thalamus. Finally, DBS systems were implanted in swine, and FUS lesioning was targeted to the contralateral thalamus, MRI was used to assess the treatments, and histological analyses were performed at 2 days and at 1 month. Results: In gel experiments and cadavers, FUS resulted in target heating to 29-32°C without any heating at the electrode. In animal experiments, there were no FUS-related MRI signal changes near the electrode. Histological analysis showed typical FUS lesions with no evidence of damage surrounding the electrode tracts. Conclusions: FUS is feasible in the setting of a preimplanted DBS device. There was minimal heating of the device during the procedure and no apparent FUS-related tissue injury.