Objective: To quantify the improvement of different types of tremor in upper limb using the spectrum of accelerometer signal in patients treated with unilateral lesions of the ventral intermediate nucleus of the thalamus (thalamotomy) by magnetic resonance guided focused ultrasound (MRgFUS).

Background: In spite of several reports showing the reduction of tremor severity using validated scores, there are no studies about the electrophysiological characterization of tremor before and after this treatment.

Method: Nineteen patients with upper limb tremor (13 with essential tremor (ET) and 6 with tremor dominant Parkinson’s disease (PD)) treated with unilateral thalamotomy by MRgFUS were included in this study. Tremor was recorded with three triaxial accelerometers located on the fingers (distal), elbow (medium), and shoulder (proximal) of the contralateral arm in three different conditions: at rest, maintaining the elbow flexed parallel to the floor, and during the action of drinking water from a bottle in order to study rest, postural and action tremor respectively. Recordings were obtained before and 1 month after the treatment. Spike2 programme was used for recording and analysis. The signals of each accelerometer were transformed into a unique vector by location. Frequencies under 3 and over 12 Hz were excluded and the power of the highest peak frequency was selected for the analysis. A repeated-measures multivariate ANOVA was used to compare the mean power among the three tremor types and the three locations.

Results: At baseline, patients with ET showed a significant predominance of postural and action tremor, whereas in patients with PD there was no difference between the types of tremor. In both groups there was also a statistically significant differences between the intensity in the fingers, respecting to the other locations (p<0.001).
After the MRgFUS the intensity of tremor decreased 2-3 orders of magnitude in both PD and ET patients, regardless of the type and location of tremor (p<0.001). In patients with ET the improvement was higher in postural and action tremor (p=0.023). In patients with PD the improvement was higher in rest and postural tremor (p=0.058) and in the distal (fingers) location.

Conclusion: MRgFUS thalamotomy in patients with PD and ET is an effective technique for the reduction of tremor whatever its type or location is.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/quantitative-study-of-the-effect-of-thalamotomy-by-mrgfus-in-the-different-types-and-locations-of-tremor-in-the-contralateral-upper-limb/