Transcutaneous Direct Current Stimulation Research Articles

Model-guided transcutaneous direct current stimulation of the brain and spinal cord to repair ALS-induced motor dysfunctions

Model-guided transcutaneous direct current stimulation of the brain and spinal cord to repair ALS-induced motor dysfunctions

Glutamatergic System in Depression and Its Role in Neuromodulatory Techniques Optimization.

Depressive disorders are among the most common psychiatric conditions and contribute to significant morbidity. Even though the use of antidepressants revolutionized the management of depression and had a tremendous positive impact on the patient's outcome, a significant proportion of patients with major depressive disorder (MDD) show no or partial or response even with adequate treatment. Given the limitations of the prevailing monoamine hypothesis-based pharmacotherapy, glutamate and glutamatergic related pathways may offer an alternative and a complementary option for designing novel intervention strategies. Over the past few decades, there has been a growing interest in understanding the neurobiological underpinnings of glutamatergic dysfunctions in the pathogenesis of depressive disorders and the development of new pharmacological and non-pharmacological treatment options. There is a growing body of evidence for the efficacy of neuromodulation techniques, including transcranial magnetic stimulation, transcutaneous direct current stimulation, transcranial alternating current stimulation, and photo-biomodulation on improving connectivity and neuroplasticity associated with depression. This review attempts to revisit the role of glutamatergic neurotransmission in the etiopathogenesis of depressive disorders and review the current neuroimaging, neurophysiological and clinical evidence of these neuromodulation techniques in the pathophysiology and treatment of depression.

Comparison of Treatment Outcome between Repetitive Transcranial Magnetic Stimulation (rTMS) and Transcutaneous Direct Current Stimulation (tDCS) in Intractable Tinnitus.

Repetitive transcranial magnetic stimulation (rTMS) and transcutaneous direct current stimulation (tDCS) are non-invasive treatments for chronic tinnitus based on neuromodulation of cortical activity. Both are considered effective, but with heterogeneous results due to lack of established protocols. Because the target groups for both modalities overlap, it is difficult to recommend one of them. We tried to unify the inclusion criteria and treatment schedules to compare the two modalities. The medical charts of 36 patients who underwent rTMS as part of clinical routine were reviewed and data for 34 patients who underwent tDCS about 7 years later were collected prospectively. Both groups had chronic unilateral tinnitus refractory to medication. Patients were treated for 5 consecutive days, and tinnitus symptoms were evaluated by survey both at the end of the treatment schedule and 1 month after the treatment. The ratio of responders who showed >20% reduction in tinnitus handicap inventory scores were compared. At the end of the treatment, the rTMS group showed a rapid response compared to the tDCS group (rTMS, 30.6%; tDCS, 12.1%; p = 0.054). However, both groups showed a significant and similar reduction in tinnitus symptoms 1 month after the treatment (rTMS, 47.2%; tDCS, 36.4%; p = 0.618). As both groups showed comparable results for tinnitus reduction, tDCS may be superior in terms of cost-effectiveness.

Transcutaneous Direct Current Stimulation of the Spinal Cord for Treatment of Spasticity in Multiple Sclerosis

Transcutaneous Direct Current Stimulation of the Spinal Cord for Treatment of Spasticity in Multiple Sclerosis

P50-T Changes in peripheral nerve excitability by transcutaneous direct currents in healthy subjects – pilot study

Background Anodal stimulation results in subthreshold depolarisation, while cathodal stimulation hyperpolarises neuronal membranes. There have been few studies on the possible modulatory effect of long lasting transcutaneous direct current stimulation on the axonal membrane properties of peripheral nerves, especially on the possible modulatory effect of such currents. We aimed to assess the applicability, safety and effects on axonal membrane excitability of transcutaneous peripheral nerve stimulation with direct currents (pDCS). Material and methods We included 15 healthy subjects. pDCS was performed with the active electrode placed over the forearm and the reference electrode on the back of the hand using 5 × 5 cm rubber electrodes. The current applied was 2.5 mA during 15 min. Following a sham stimulation, two different settings were randomly used, cathodal and anodal current. Excitability measurements were performed using the TRONDNF nerve excitability protocol of the QTRAC program. Results The protocol was completed and well tolerated in all subjects. The TEd (90–100 ms) was significantly lower for anodal stimulation (p = 0.04). There were no other significant differences. These results were not replicated in a repeated trial, and in addition multiTRAC assessment failed to demonstrate significant after-effects on excitability. Conclusions TEd 90–100 ms reflects function of slow K+ channels, mainly located at the nodes. Initial findings suggested that slow K+-channel expression or conductance may be reduced after the application of anodal DC current, however repeated studies and real-time assessment of excitability measures argue against a consistent effect. Further research should be performed, using different intensities and stimulation time, as well as other excitability measurements.

Direct current stimulation modulates the excitability of the sensory and motor fibres in the human posterior tibial nerve, with a long-lasting effect on the H-reflex.

Several studies demonstrated that transcutaneous direct current stimulation (DCS) may modulate central nervous system excitability. However, much less is known about how DC affects peripheral nerve fibres. We investigated the action of DCS on motor and sensory fibres of the human posterior tibial nerve, with supplementary analysis in acute experiments on rats. In forty human subjects, electric pulses at the popliteal fossa were used to elicit either M-waves or H-reflexes in the Soleus, before (15min), during (10min) and after (30min) DCS. Cathodal or anodal current (2mA) was applied to the same nerve. Cathodal DCS significantly increased the H-reflex amplitude; the post-polarization effect lasted up to ~25min after the termination of DCS. Anodal DCS instead significantly decreased the reflex amplitude for up to ~5min after DCS end. DCS effects on M-wave showed the same polarity dependence but with considerably shorter after-effects, which never exceeded 5min. DCS changed the excitability of both motor and sensory fibres. These effects and especially the long-lasting modulation of the H-reflex suggest a possible rehabilitative application of DCS that could be applied either to compensate an altered peripheral excitability or to modulate the afferent transmission to spinal and supraspinal structures. In animal experiments, DCS was applied, under anaesthesia, to either the exposed peroneus nerve or its Dorsal Root, and its effects closely resembled those found in human subjects. They validate therefore the use of the animal models for future investigations on the DCS mechanisms.

P066 Polarity-specific modulation of central pain processing by transcranial direct current stimulation

Background Transcutaneous direct current stimulation (tDCS) is a known tool for inducing changes in cortical excitability influencing motor as cognitive functions. Previous studies suggest that application of tDCS might be a therapeutic approach for pain disorders as well. Objective The aim of the study was to investigate pain-related changes in cerebral activation pattern and its modulation by direct current stimulation. Methods Thirteen right-handed healthy participants received 20 min of tDCS applied over primary motor cortex (M1) under three different conditions which are anodal-tDCS, cathodal-tDCS, and sham-tDCS in a blinded cross-over design. Afterwards tDCS neural response to electric trigeminal pain stimulation was investigated using a block designed fMRI. Between the three tDCS conditions a time interval of at least 2 months was kept. Results All pain stimulation showed distinct activation pattern in the established brain areas of pain processing. Following anodal tDCS increased activation was detected in different part of the pain processing network including thalamus, basal ganglia, cingulate cortex, dorsolateral prefrontal cortex, and amygdala while cathodal t-DCS showed decreased BOLD response in these pain processing areas. Behavioral data were not changed irrespective of tDCS stimulation mode. Discussion Our study shows polarity-specific modulation of cerebral pain processing, which are in line with previous electrophysiological data. Anodal tDCS leads to an increased activation of the central pain-network compared to cathodal tDCS. Our results contribute to a network-based understanding of the underlying mechanism in tDCS.

Surgical Neurostimulation for Spinal Cord Injury.

Traumatic spinal cord injury (SCI) is a devastating neurological condition characterized by a constellation of symptoms including paralysis, paraesthesia, pain, cardiovascular, bladder, bowel and sexual dysfunction. Current treatment for SCI involves acute resuscitation, aggressive rehabilitation and symptomatic treatment for complications. Despite the progress in scientific understanding, regenerative therapies are lacking. In this review, we outline the current state and future potential of invasive and non-invasive neuromodulation strategies including deep brain stimulation (DBS), spinal cord stimulation (SCS), motor cortex stimulation (MCS), transcutaneous direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) in the context of SCI. We consider the ability of these therapies to address pain, sensorimotor symptoms and autonomic dysregulation associated with SCI. In addition to the potential to make important contributions to SCI treatment, neuromodulation has the added ability to contribute to our understanding of spinal cord neurobiology and the pathophysiology of SCI.

66. Effects of cranio-spinal tDCS in the treatment of cognitive and motor symptoms in early Huntington’s Disease

Transcutaneous Direct Current Stimulation (tDCS) is a safe technique for modulating central nervous system excitability. We assessed clinical changes in early Huntington’s Disease (HD) following tDCS by evaluating Unified Huntington Disease Rating Scale (UHDRS). tDCS electrodes were applied over the thoracic spinal cord (T9–T11) and parietal cortex of right hemisphere, respectively as anode and cathode. We applied current at a density of 0.071 mA/cm2 and delivered a total charge density of 85.7 mC/cm2. The stimulation consisted in a daily session of treatment during 5 days, of 20 min (2.0 mA) each one. The clinical evaluation was performed before tDCS (T0), after 5 days of treatment (T1) and after 2 weeks from the last session (T2). After tDCS a significant improvement both in motor (T0 vs. T1: 17 vs. 12) and behavioral scores was found (T0 vs. T1 vs. T2: 25 vs. 18 vs. 13). We showed significant effects of tDCS on motor and behavioral symptoms in early HD. The configuration we used likely reduces the abnormal peripheral afferent input, possibly restoring at the same time the balance of interhemispheric communication by interfering with right parietal hyperactivity.

Noninvasive Spinal Cord Stimulation: Technical Aspects and Therapeutic Applications.

Electrical and magnetic trans-spinal stimulation can be used to increase the motor output of multiple spinal segments and modulate cortico-spinal excitability. The application of direct current through the scalp as well as repetitive transcranial magnetic stimulation are known to influence brain excitability, and hence can also modulate other central nervous system structures, including spinal cord. This study aimed to evaluate the effects and the therapeutic usefulness of these noninvasive neuromodulatory techniques in healthy subjects and in the neurorehabilitation of patients with spinal cord disorders, as well as to discuss the possible mechanisms of action. A comprehensive review that summarizes previous studies using noninvasive spinal cord stimulation is lacking. PubMed (MEDLINE) and EMBASE were systematically searched to identify the most relevant published studies. We performed here an extensive review in this field. By decreasing the spinal reflex excitability, electrical and magnetic trans-spinal stimulation could be helpful in normalizing reflex hyperexcitability and treating hypertonia in subjects with lesions to upper motor neurons. Transcutaneous spinal direct current stimulation, based on applying direct current through the skin, influences the ascending and descending spinal pathways as well as spinal reflex excitability, and there is increasing evidence that it also can induce prolonged functional neuroplastic changes. When delivered repetitively, magnetic stimulation could also modulate spinal cord functions; however, at present only a few studies have documented spastic-reducing effects induced by repetitive spinal magnetic stimulation. Moreover, paired peripheral and transcranial stimulation can be used to target the spinal cord and may have potential for neuromodulation in spinal cord-injured subjects. Noninvasive electrical and magnetic spinal stimulation may provide reliable means to characterize important neurophysiologic and pathophysiologic aspects of spinal cord function. Moreover, transcutaneous direct current stimulation and repetitive magnetic stimulation may hold therapeutic promise in patients with spinal cord disorders, although future well-controlled studies are needed to corroborate and extend the preliminary findings.

P261: Transcutaneous direct current stimulation on cervical spinal cord: effects on H-reflex and spinal reflexes

P261: Transcutaneous direct current stimulation on cervical spinal cord: effects on H-reflex and spinal reflexes

Poster 20 Changes in Motor-evoked Potential Induced by Non-invasive Transcutaneous Direct Current Stimulation of the Neck

Poster 20 Changes in Motor-evoked Potential Induced by Non-invasive Transcutaneous Direct Current Stimulation of the Neck

Transcutaneous spinal cord direct current stimulation inhibits the lower limb nociceptive flexion reflex in human beings

Aiming at developing a new, noninvasive approach to spinal cord neuromodulation, we evaluated whether transcutaneous direct current (DC) stimulation induces long-lasting changes in the central pain pathways in human beings. A double-blind crossover design was used to investigate the effects of anodal direct current (2mA, 15min) applied on the skin overlying the thoracic spinal cord on the lower-limb flexion reflex in a group of 11 healthy volunteers. To investigate whether transcutaneous spinal cord DC stimulation (tsDCS) acts indirectly on the nociceptive reflex by modulating excitability in mono-oligosynaptic segmental reflex pathways, we also evaluated the H-reflex size from soleus muscle after tibial nerve stimulation. In our healthy subjects, anodal thoracic tsDCS reduced the total lower-limb flexion reflex area by 40.25% immediately after stimulation (T0) and by 46.9% 30min after stimulation offset (T30). When we analyzed the 2 lower-limb flexion reflex components (RII tactile and RIII nociceptive) separately, we found that anodal tsDCS induced a significant reduction in RIII area with a slight but not significant effect on RII area. After anodal tsDCS, the RIII area decreased by 27% at T0 and by 28% at T30. Both sham and active tsDCS left all the tested H-reflex variables unchanged. None of our subjects reported adverse effects after active stimulation. These results suggest that tsDCS holds promise as a tool that is complementary or alternative to drugs and invasive spinal cord electrical stimulation for managing pain.Thoracic transcutaneous direct current stimulation induces depression of nociceptive lower limb flexion reflex in human beings that persists after stimulation offset; this form of stimulation holds promise as a tool that is complementary or alternative to drugs and invasive spinal cord electrical stimulation for managing pain.

Effect of spinal transcutaneous direct current stimulation on somatosensory evoked potentials in humans

Objective Invasive stimulation of the spinal cord is used to treat a number of pathological conditions. Aiming to modulate human spinal cord function non-invasively, we evaluated whether transcutaneous direct current (DC) stimulation induces long-lasting changes in conduction along the sensory spinal pathways. Methods Somatosensory evoked potentials (SEPs) by posterior tibial nerve and by median nerve stimulation were recorded, before, at current offset and at 20 min after transcutaneous anodal or cathodal DC stimulation over the thoracic spinal cord (2.5 mA, 15 min) in a group of 12 healthy subjects. Results Whereas both polarities left the spinal (N22) and the cortical potentials (P39) unchanged, anodal transcutaneous spinal DC stimulation decreased significantly by about 25% the amplitude of the cervico-medullary component of posterior tibial nerve SEPs (P30) for at least 20 min. Thoracic transcutaneous spinal cord stimulation left median nerve SEPs unchanged. Conclusions Transcutaneous DC stimulation over the thoracic spinal cord induces changes in conduction along human lemniscal pathway that persist after stimulation ends. Significance Our results support the use of transcutaneous DC stimulation as a novel tool for non-invasive spinal neuromodulation. Because the method is non-expensive and simple, it can be tested in patients with disorders presently treated with invasive procedures.