Objective: Tremor can be a disabling motor symptom in patients with Parkinson´s disease (PD) and in some patients is refractory to medication. Here we present a pilot study on the potential of peripheral electrical stimulation to reduce pathological tremor in two PD patients.

Background: Recently, electrical stimulation of afferent pathways has been explored as a potential approach for tremor reduction [1] [2]. We have recently demonstrated the potential of selective and adaptive timely stimulation (SATS) in essential tremor patients, with some of these patients sustaining tremor reduction 24h after stimulation trials [3].

Method: Two PD patients with rest and postural tremor (one female and one male, 50 and 59 years old) were recruited from Gregorio Marañón Hospital (Madrid, Spain). All procedures were approved by the hospital ethics committee. Surface electromyography (sEMG) electrodes were placed over flexor carpi radialis and extensor carpi radialis of the side most affected by tremor. Surface stimulation electrodes were placed over the radial and the median nerves. An embedded control unit including an electrical stimulator and an EMG amplifier was used to record sEMG signals at 2 kHz and provide biphasic stimulation of 100 Hz and 400 µs of pulse width. Four inertial measurement units were placed in the chest, lateral side of the arm, forearm, and dorsal side of the hand to quantify changes in tremor amplitude. Each patient was asked to maintain the arms in a position that would elicit the greatest tremor amplitude. Several SATS out-of-phase (i.e., stimulation of the antagonist muscle to the one presenting tremor) trials were performed on each patient (30 seconds of stimulation; 7 and 6 trials for patients 1 and 2, respectively). Clinical evaluation was performed before and immediately after the stimulation.

Results: Both patients experienced a significant tremor reduction in all joints after stimulation trials (see [figure1] and [figure2]). For patient 1, the reduction was greater in the shoulder joint. Patient 2 showed considerable tremor reduction in all joints. Moreover, both patients improved in the clinical assessment.

Conclusion: These preliminary results suggest that SATS via peripheral electrical stimulation may induce an acute reduction of the postural component of PD tremor.
This work was supported by the EU Horizon 2020 research and innovation programme (Project EXTEND, Grant 779982).

References: [1] Muceli, S., Poppendieck, W., Hoffmann, K. P., Dosen, S., Benito-León, J., Barroso, F. O., Pons, J. L., Farina, D. (2019). A thin-film multichannel electrode for muscle recording and stimulation in neuroprosthetics applications. Journal of neural engineering, 16(2), 026035.
[2] Pascual-Valdunciel, A., Hoo, G. W., Avrillon, S., Barroso, F. O., Goldman, J. G., Hernandez-Pavon, J. C., Pons, J. L. (2021). Peripheral electrical stimulation to reduce pathological tremor: a review. Journal of neuroengineering and rehabilitation, 18(1), 1-19.
[3] Pascual-Valdunciel, A., González-Sánchez, M., Muceli, S., Adán-Barrientos, B., Escobar-Segura, V., Pérez-Sánchez, J. R., Jung, M. K., Schneider, A., Hoffmann, K. P., Moreno, J. C., Grandas, F., Farina, D., Pons, J. L., Barroso, F. O. (2020). Intramuscular stimulation of muscle afferents attains prolonged tremor reduction in essential tremor patients. IEEE Transactions on Biomedical Engineering, 68(6), 1768-1776.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/novel-strategies-based-on-sensory-electrical-stimulation-to-manage-tremor-in-parkinsons-disease-a-pilot-study/