Objective: To study the effects of MRI-guided High Frequency Focused Ultrasound on Center of Pressure measurements obtained using force plates.

Background: MRI-Guided High Frequency Focused Ultrasound (MRgFUS) therapy thalamotomy in the Ventral Intermediate Nucleus of thalamus has been approved for treatment of tremor in Essential tremor (ET) and Parkinson’s disease (PD)[2]. However, a potential side effect of this therapy is gait/balance impairment. Center of pressure (COP) variability may be related to fall risk especially in older populations [1].  Therefore, we aimed to investigate if COP measures changed after unilateral MRgFUS thalamotomy at a single center using force plates in static posturography.

Method: Six patients (ET: n = 5; PD: n = 1) who underwent MRgFUS underwent static posturography before the intervention and again approximately a year post-intervention to assess COP measures. COP measurement was conducted in a 3D motion lab [3] at a tertiary center with two research-grade AMTI 6-axis force plates. Patients stood stationery with their eyes open and feet in a standardized position for 60 seconds. The following COP measurements were obtained: 1)mean distance of sway in the antero-posterior (MDist AP) and medio-lateral (MDist ML) directions, as well as the average of AP and ML (MDist) directions 2) range of sway in the antero-posterior (Range AP) and medio-lateral (Range ML) directions, as well as the average of AP and ML (Range) directions, 3) maximum distance of sway from center (MaxDist). Pre- and post-procedure differences were assessed using paired sample t-tests.

Results: Patients were on average 75 (±5.2) years old and were seen 15 (±2.9) months apart. No significant changes were noted in the COP measure pre and post intervention using two-tailed paired sample t-tests (p>0.05) (Figure 1).

Conclusion: This case series provides data regarding COP measures before and after MRgFUS interventions. No degradation in measures of static posturography were observed. This case series has a small sample size. Future studies will aim to look at clinical outcomes in a larger population, including fall outcomes.

Table 1

Figure 1

References: [1] Quijoux F, Vienne-Jumeau A, Bertin-Hugault F, Zawieja P, Lefevre M, Vidal PP, Ricard D (2020) Center of pressure displacement characteristics differentiate fall risk in older people: A systematic review with meta-analysis. Ageing Res Rev 62, 101117.
[2] Elias WJ, Lipsman N, Ondo WG, Ghanouni P, Kim YG, Lee W, Schwartz M, Hynynen K, Lozano AM, Shah BB, Huss D, Dallapiazza RF, Gwinn R, Witt J, Ro S, Eisenberg HM, Fishman PS, Gandhi D, Halpern CH, Chuang R, Butts Pauly K, Tierney TS, Hayes MT, Cosgrove GR, Yamaguchi T, Abe K, Taira T, Chang JW (2016) A Randomized Trial of Focused Ultrasound Thalamotomy for Essential Tremor. N Engl J Med 375, 730-739.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/static-posturography-changes-following-unilateral-mri-guided-high-frequency-focused-ultrasound-thalamotomy-case-series/