Abstract
Dysfunction within large-scale brain networks as the basis for movement disorders is an accepted hypothesis. The treatment options for restoring network function are limited. Non-invasive brain stimulation techniques such as repetitive transcranial magnetic stimulation are now being studied to modify the network. Transcranial electrical stimulation (tES) is also a portable, cost-effective, and non-invasive way of network modulation. Transcranial direct current stimulation and transcranial alternating current stimulation have been studied in Parkinson’s disease, dystonia, tremor, and ataxia. Transcranial pulsed current stimulation and transcranial random noise stimulation are not yet studied enough. The literature in the use of these techniques is intriguing, yet many unanswered questions remain. In this review, we highlight the studies using these four potential tES techniques and their electrophysiological basis and consider the therapeutic implication in the field of movement disorders. The objectives are to consolidate the current literature, demonstrate that these methods are feasible, and encourage the application of such techniques in the near future.
Highlights
In movement disorders, non-invasive brain stimulation (NIBS) is an evolving therapeutic strategy
With stimulation of the motor cortex by cathodal transcranial direct current stimulation (tDCS) (1.5 mA, 15 min, five sessions) followed by transcranial alternating current stimulation (tACS), a 54% reduction in the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) and a 75% reduction in the TWSTRS Pain Scale was noted in a patient of idiopathic cervical dystonia, and the effects persisted at 30 days of follow-up (Angelakis et al, 2013)
The efficacy of tDCS has been tested in dystonia and cerebellar ataxia (11 studies for each), but the number of studies for other movement disorders like essential tremor (ET), orthostatic tremor (OT), Huntington’s disease (HD), multisystem atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal syndrome (CBS) is quite less
Summary
Non-invasive brain stimulation (NIBS) is an evolving therapeutic strategy. Movement disorders such as Parkinson’s disease (PD) (de Schipper et al, 2018), dystonia (Schirinzi et al, 2018), tremor (Benito-León et al, 2015), and ataxia (Falcon et al, 2016; Wu et al, 2018) may fit very well within this construct of network dysfunction to explain the pathophysiology and phenotypes This paradigm shift of suggesting that the movement disorders are a result of dysfunction in multilevel, interconnected complex cortico-subcortical network rather than only being restricted to the basal ganglia has opened the possibility of modifying that network noninvasively by delivering electromagnetic stimulation. We have explained their electrophysiological basis and highlighted the unmet needs for promoting tES as a new therapeutic intervention
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