Objective: To assess the feasibility and safety of bilateral staged focused ultrasound subthalamotomy(FUS-STN) for Parkinson’s disease(PD).

Background: Unilateral FUS-STN for PD improves contralateral motor features as demonstrated in randomized controlled trial. The feasibility of bilateral FUS-STN aiming to treat both sides of the body remains unexplored.

Method: Prospective, open-label study. PD patients who had previously been treated with unilateral FUS-STN and who developed medical-refractory motor signs in the untreated hemibody were included. Primary outcomes were safety and efficacy according to the motor MDS-UPDRS in the off-med state 6 months after the second FUS-STN. Secondary outcomes included motor complications(MDS-UPDRS IV),PD-related disability(MDS-UPDRS II),quality of life(PDQ39) and dopaminergic drug change. Non-parametric Wilcoxon-signed rank test was applied.

Results: Six PD patients(mean age 52.6+6.5ys, 6.0+2.6 of disease evolution at first treatment) underwent bilateral staged FUS-STN(mean time between FUS 2.7+1.2ys). After the second treatment, three patients developed dyskinesias on the contralateral upper limb. In one of them, dyskinesia also affected the leg interfering with gait. In all cases, dyskinesias totally resolved in 3 months. Two patients developed mild slurred speech which progressively improved being minimal at 6 months. No cognitive or behavioural disturbances were found in the neuropsychological testing. MDS-UPDRS III improved by 49.2% between baseline and 6 months after the second FUS-STN(from 38.5.0+7.6 to 18.7+11.0,p=0.031) leading to a positive impact on quality of life(PDQ39,from 18.9+8.1 to 12.5+11.0,p=0.047). If the pre-procedure score of the secondly treated side was considered in baseline MDS-UPDRS III, improvement were higher(60.5%,from 46.7+3.1 to 18.7+11.0,p=0.016). Motor complications showed a trend towards improvement from baseline(MDS-UPDRS IV from 4.5+3.6 to 2.3+2.5,p=0.053). Independence in daily living remained stable(MDS-UPDRS II 10.5+5.6 to 7.6+8.0,p=0.109). At last follow-up,mean levodopa equivalent daily dose and levodopa requirements were not significantly reduced(662.02±357.9 to 521.2±408.9mg,p=0.281;400.0+270.2 to 233.3+238.0mg,p=0.219,respectively).

Conclusion: Bilateral staged FUS-STN for PD is feasible and might be safe and effective to improve cardinal motor features bilaterally as well as quality of life. A larger trial is warranted to confirm these results.

References: Álvarez et al, 2009 JNNP
Martínez-Fernández et al, 2018 Lancet
Martínez-Fernández et al, 2020 New England of Medicine

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MDS Abstracts - https://www.mdsabstracts.org/abstract/bilateral-staged-mri-guided-focused-ultrasound-subthalamotomy-for-parkinsons-disease/