Objective: To assess the effect of MRI-guided Focused Ultrasound (MRIgFUS) unilateral subthalamotomy on Parkinson disease’s (PD) motor features through EMG movement analysis.

Background: Recent evidence suggests that MRIgFUS unilateral subthalamotomy can safely improve PD motor features according to the MDS-UPDRS III ¹. A proper way to quantitatively measure motor performance is through EMG movement analysis.

Methods: PD patients who were selected for MRIgFUS unilateral subthalamotomy were analyzed in the OFF-medication state at baseline and six months after treatment. Patients performed two tasks while surface EMG was recorded: upper limb ballistic movement and 10-second finger tapping. Proximal simple reaction time after an acoustic signal and number, amplitude and rhythmicity of taps were recorded. All measurements were assessed on both sides of the body (ipsilateral/contralateral to the subthalamotomy). Off-line analysis was blinded to treated/untreated side. Comparison was done by means of t-test for paired samples.

Results: Seven patients (4 male) were included in the study. Mean age was 62.5 years (range 42-70) with a mean disease evolution of 6.4 years (range 3-10). Distal simple reaction time in the treated body side improved from 176 ± 23 ms at baseline to 140 ± 23 ms at 6 months (a mean reduction of 20%, p=0.02). No change was found in reaction time in the untreated hemibody. While the number of taps between both hands differed at baseline (29 ± 8 for the most impaired hemibody vs 34 ± 11 for the less affected, p=0.01), it was equivalent between the treated and untreated body side at 6 months (39.2 ± 9 vs 40.2 ± 11 respectively, p=0.08 ). Moreover, the number of taps in the treated hand significantly increased after subthalamotomy (34.4% improvement). Rhythmicity in the treated body side improved by 6 months (0.119 vs 0.092 of tapping variability) without reaching statistical significance (p=0.2).

Conclusions: This study shows that MRIgFUS subthalamotomy improves PD motor features measured with EMG movement analysis. These findings support the clinical motor improvement assessed through the MDS-UPDRS III.

References: 1- Focused ultrasound subthalamotomy in patients with asymmetric Parkinson’s disease: a pilot study. Martínez-Fernández, Raul et al. The Lancet Neurology , Volume 17 , Issue 1 , 54 – 63.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/effects-of-mri-guided-focused-ultrasound-unilateral-subthalamotomy-on-characteristics-of-emg-activity-underlying-reaction-time-and-tapping-test-in-parkinsons-disease/