Magnetic resonance-guided focused ultrasound for Parkinson's disease since ExAblate, 2016-2019: a systematic review

ExAblate received FDA approval for treatment of a range of movement disorders in 2016, including tremor-dominant Parkinson's disease (TDPD), dyskinetic PD, and essential tremor. This incisionless device allows for magnetic resonance-guided focused ultrasound (MRgFUS) for ablation of several regions of interest. Current studies should aim to measure pre- and post-operative neurocognitive functioning to better understand MRgFUS in PD and how it compares to deep brain stimulation, which has known cognitive risks among certain populations.

PubMed, CINAHL, PsycINFO, and Cochrane Library databases were searched from January 2016 to January 2020. Guidelines for Preferred Reporting Items for Systematic Review and Meta-Analyses were used to review clinical trials comprehensively assessing pre- and post-operative neurocognitive functioning in PD patients undergoing MRgFUS. Due to limited extant literature in this area, TDPD was expanded to PD with severe dyskinesia.

Twenty-two abstracts were reviewed following removal of duplicates. After full-text review of eight articles, only two studies included comprehensive neuropsychological evaluations of PD patients undergoing MRgFUS thalamotomy or pallidotomy. Most excluded studies used only brief cognitive screeners to assess functioning. Cognitive declines appear to be minimal following MRgFUS in PD, with exceptions in verbal fluency and inhibition. These results are limited by sample size and sample diversity.

Significant methodological gaps were inadvertently discovered. Few studies to-date have administered comprehensive neuropsychological batteries to ascertain MRgFUS risks to neurocognitive functioning in PD. Studies must extend beyond brief screeners when assessing PD populations vulnerable to decline. Furthermore, consensus on a comprehensive battery would better serve replicability and the ability to engage in useful meta-analyses.