Abstract
Parkinsonian tremor is one of the most common motor disorders in patients with Parkinson's disease (PD). Compared to oral medications and brain surgery, electrical stimulation approaches have emerged as effective and non-invasive methods for tremor reduction. The pathophysiology, detection and interventions of tremors have been introduced, however, a systematic review of peripherical electrical stimulation approaches, methodologies, experimental design and clinical outcomes for PD tremor suppression is still missing. Therefore, in this paper, we summarized recent studies on electrical stimulation for tremor suppression in PD patients and discussed stimulation protocols and effectiveness of different types of electrical stimulation approaches in detail. Twenty out of 528 papers published from 2010 to 2021 July were reviewed. The results show that electrical stimulation is an efficient intervention for tremor suppression. The methods fall into three main categories according to the mechanisms: namely functional electrical stimulation (FES), sensory electrical stimulation (SES) and transcutaneous electrical nerve stimulation (TENS). The outcomes of tremor suppression were varied due to various stimulation approaches, electrode locations and stimulation parameters. The FES method performed the best in tremor attenuation where the efficiency depends mainly by the control strategy and accuracy of tremor detection. However, the mechanism underlying tremor suppression with SES and TENS, is not well-known. Current electrical stimulation approaches may only work for a number of patients. The potential mechanism of tremor suppression still needs to be further explored.
Highlights
Parkinson’s disease (PD) is a progressive degenerative disease characterized by a substantial loss of dopaminergic neurons in in the substantia nigra resulting in motor dysfunctions (Tysnes and Storstein, 2017; Galvez et al, 2018), such as tremor, bradykinesia, posture instability and gait difficulties (Chapuis et al, 2005; Ly et al, 2016; Carvajal-Castano et al, 2021; Zhang et al, 2021)
A total of 282 articles were retrieved from the Web of Science database while 158, 67, and 21 articles obtained from the PubMed, Embase and Institute of Electrical and Electronics Engineers (IEEE) database, respectively, with the use of the above retrieval method
After duplicate and unrelated papers were removed after initial screening, 23 articles were excluded according to the criteria: 8 articles were excluded according to criterion (i), 10 articles were excluded according to criterion (ii), and 5 articles were excluded according to criterion (iii)
Summary
Parkinson’s disease (PD) is a progressive degenerative disease characterized by a substantial loss of dopaminergic neurons in in the substantia nigra resulting in motor dysfunctions (Tysnes and Storstein, 2017; Galvez et al, 2018), such as tremor, bradykinesia, posture instability and gait difficulties (Chapuis et al, 2005; Ly et al, 2016; Carvajal-Castano et al, 2021; Zhang et al, 2021). Tremors usually occur in the hands and have a significant effect on daily life (Louis and Machado, 2015). Levodopa is considered mostly effective for PD tremor in combination with carbidopa (Marjama-Lyons and Koller, 2000; Fishman, 2008). The efficiencies of medication are various among patients. It may even worsen in some patients (Fahn et al, 2004; Hallett, 2012). Invasive techniques, such as deep brain stimulation (DBS), has been proven effective for tremor reduction (O’Connor and Kini, 2011). Brain surgery has high risk and requires appropriate surgical indications (Okun et al, 2005; Hariz et al, 2008; Bronstein et al, 2011)
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