Objective: 1. To characterise electrophysiological features of functional tremor during cognitive and motor tasks.

2. To evaluate immediate and longitudinal effects of low-frequency rTMS on tremor metrics using accelerometry (ACC) and surface electromyography (sEMG).

Background: Functional tremor (FT) is the most common functional movement disorder, characterised by variable frequencies, distractibility, and entrainment. Repetitive transcranial magnetic stimulation (rTMS) has shown therapeutic potential in functional tremor. However, objective quantification of tremor response remains limited.

Method: 10 FT patients were included in the study. Tremor recordings before and after rTMS were obtained using ACC and sEMG from the respective muscles involved in tremor—ECR and FCR for hand tremor (n=9), and tibialis anterior and gastrocnemius for leg tremor (n=1)— during rest, forward-hold, cognitive task, and motor task of unaffected limb. All patients subsequently received inhibitory rTMS (0.5 Hz, 600 pulses at 100% RMT) over contralateral primary motor cortex (M1).

2 of 10 patients consented to undergo 10 & 15 rTMS sessions, and their tremor was recorded longitudinally at each time point. Tremor amplitude and dominant frequency were extracted. Wilcoxon signed-rank test was performed.

Results: 40% of FT patients showed 48% reduction in tremor amplitude during cognitive task. All patients showed 61% reduction in tremor amplitude during motor task.

Single-session rTMS significantly reduced tremor amplitude across both rest and postural conditions. Tremor amplitude (RMS) was decreased by 45.3% (p = 0.037) at rest and 36.2% (p = 0.014) during forward hold. Peak-to-peak tremor amplitude decreased (rest: 45.7%, p = 0.049; forward hold: 35.0%, p = 0.020). Dominant tremor frequency remained unchanged (p > 0.05).

In Patient 1, rest tremor amplitude decreased by 97.4% at Day 10 and 97.3% at Day 15, while postural tremor amplitude decreased by 69.5% at Day 10 and 95.1% at Day 15.

In Patient 2, rest tremor amplitude decreased by 40.2% at Day 10 and 62.9% at Day 15, while postural tremor amplitude improved from −18.9% to −27.1%.

Conclusion: This ongoing study demonstrates that inhibitory rTMS over contralateral M1 can suppress tremor amplitude in functional tremor. Longitudinal observations further suggest progressive tremor reduction with repeated sessions, supporting rTMS as a potential therapeutic intervention.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/effect-of-low-frequency-rtms-on-functional-tremor-objective-evidence-from-a-single-session-and-longitudinal-observations/