To evaluate the tolerability and efficacy of an accelerated schedule of theta burst focused ultrasound stimulation (tbTUS) delivered to the primary motor cortex in Parkinson’s disease (PD) patients assessed by transcranial magnetic stimulation (TMS) and United Parkinson’s Disease Rating Scale (UPDRS)-Part III.

Low intensity transcranial focused ultrasound stimulation (TUS) is an emerging technology for non-invasive brain stimulation (NIBS) that can penetrate deeper in the brain with more focal stimulation compared to currently used forms of NIBS. TUS delivered in a theta burst pattern (tbTUS) for 80s induces sustained increases in motor cortex excitability lasting at least 30 minutes and is a promising NIBS protocol for treatment of neurological disorders. Accelerated stimulation schedules with several treatments per day can shorten treatment duration and improve accessibility.

Three sets of tbTUS were delivered in consecutive order to the right and left primary motor cortices at 30-minute intervals. 10 PD patients attended one visit each for real and sham treatments in random order. Before and after interventions, TMS measures of motor-evoked potentials (MEP), short-interval intracortical inhibition (SICI), short-interval intracortical excitation (SICF), and UPDRS-Part III scores were collected. Patients and UPDRS raters were blinded to the stimulation condition.

Real but not sham tbTUS treatment led to increased MEP amplitude and SICF. While both conditions led to similar changes in UPDRS-III scores, rigidity subscores were reduced only with real treatment. There were no adverse effects.

The study is ongoing, and more patients are being recruited. Preliminary findings show that accelerated tbTUS is a safe and tolerable treatment schedule for PD patients. Improvements in rigidity suggests that tbTUS could be further studied as a non-invasive treatment for PD. Future research may investigate the optimal time between sonications with a longer treatment duration and a larger number of patients.