MRgFUS subthalamotomy in Parkinson's disease: an approach aimed at minimizing Lesion Volume

Abstract

Idiopathic Parkinson's Disease (PD) is a neurodegenerative disorder characterized by tremor, rigidity, bradykinesia, and postural instability. Magnetic Resonance-guided high-intensity focused ultrasound (MRgFUS) of the subthalamic nucleus (STN) is gaining recognition as a minimally invasive surgical option. This study assesses the safety and efficacy of unilateral MRgFUS subthalamotomy, aiming to create the smallest effective lesion. Between June 2021 and October 2023, twelve PD patients underwent the procedure, with primary outcomes focused on safety and motor improvements after six months. Results indicated significant motor improvements, with over 50% reduction in tremor, rigidity, and bradykinesia, while balance and gait remained stable. Quality of life also improved. Side effects were generally mild and transient, though some patients experienced involuntary movements, managed through medication adjustments. Despite limitations, this technique appears to offer a promising, less-invasive alternative for managing PD symptoms with a favorable risk-benefit profile. Further research is necessary to refine the procedure and assess long-term outcomes.

Fig. 1. Immediate post-treatment unilateral subthalamotomies.

Examples of coronal and axial T2-weighted MRI views obtained immediately after the procedure from STN10 (a), STN5 (b) and STN12 (c) participants (with different degrees of cytotoxic oedema). The site of the lesion is recognizable by a heterogeneous central area corresponding to tissue necrosis which is typically hypointense on T2-weighted image. This zone is delimited by a rim of perilesional cytotoxic oedema. The subthalamic lesions are marked with blue arrows.

Fig. 2. Effect of unilateral subthalamotomy on motor features during the 6-months follow-up.

Off-medication rigidity (A), bradykinesia (B) and tremor (C) MDS-UPDRS III subscores of the treated side (contralateral to subthalamotomy) throughout the evaluation period. Off-medication MDS-UPDRS III (D), treated side (E) and non-treated side (F). Sustained improvement was seen after subthalamotomy. Off-medication state was defined as a minimum 12 h withdrawal of standard-release anti-parkinsonian drugs and a minimum of 24 h with prolonged release formulations. Continuous values are expressed in medians, empty dots refer to extreme values. *p < 0.05; **p < 0.01; ***p < 0.001.