经颅直流电刺激的研究及应用

背景：经颅直流电刺激是一种非侵袭性的刺激脑方法,利用弱的电流经颅刺激目标区域引起脑兴奋性的改变。目的：回顾分析经颅直流电刺激的基本原理、刺激程序、优越性及不良作用及其在脑功能各个区域与脑卒中和脊髓神经系统疾病中的应用。方法：由第一作者检索1995/2011PubMed数据库及西文生物医学期刊文献数据库。检索词为＂tDCS,Transcranial Direct Current Stimulation,noninvasive brain stimulation,stroke;经颅直流电刺激,非侵袭性脑刺激＂。结果与结论：国外近十年的研究已经确立经颅直流电刺激应用于人类大脑皮质的有益效果,并基本确立了其刺激模式。阳极刺激具有兴奋大脑皮质的作用,阴极刺激降低大脑皮质的兴奋性。应用于脑卒中患者的临床研究显示阳极刺激和阴极刺激均有有益的作用,阳极刺激对脊髓损伤的患者也有有益的效果。经颅直流电刺激作为一种新的,无创的,有效的治疗方法被广泛应用于神经系统损伤患者的研究中,为这样患者的康复带来新的希望。     

基于国内经颅直流电刺激研究的文献计量学分析

正经颅直流电刺激(transcranial direct current stimulation, tDCS)是一种利用微弱电流(1—2mA)来调节大脑皮质神经细胞兴奋性的非侵袭性技术。目前,tDCS作为一种新的、无创的方法,被广泛应用于各种原因导致的神经系统损伤(如脑卒中、帕金森病、疼痛、抑郁等)及生理功能等多个领域的研究中~([1])。近年来,国内关于经颅直流电刺激的报道日     

经颅直流电刺激在脊髓损伤后神经病理性疼痛中的应用进展

经颅直流电刺激通过电流调节神经细胞跨膜电位,导致去极化或超极化,改变大脑皮质的兴奋性,从而改善脊髓损伤后神经病理性疼痛。本文主要综述经颅直流电刺激对脊髓损伤后神经病理性疼痛的作用机制、临床应用及其安全性与局限性。     

经颅直流电刺激在神经系统疾病康复中的应用现状

正经颅直流电刺激(transcranial direct current stimulation, tDCS)是一种非侵入性脑刺激技术,其由置于头皮的阴极和阳极两个表面电极片组成,以微弱的直流电作用于大脑皮质,早期的动物和临床研究发现,直流电的阳极靠近神经细胞的胞体或树突时,静息电位阈值降低,神经元放电增加;阴极使静息电位阈值增加,神经元放电减少~([1])。经颅直流电刺激具有不良反应小、刺激面积大、操作简单等优势。目前,tDCS在脑卒中、帕金森病、老年性痴呆等神经系统疾病中应用的研究不断深入,本文就其临床应用现状进行综述。     

经颅直流电刺激对吞咽失用症及皮质兴奋性的作用

目的:探讨经颅直流电刺激治疗吞咽失用症及其与大脑皮质兴奋性变化的关系。方法:采用A-B实验设计,对2例吞咽失用症患者采用经皮电刺激配合手法训练3周前后、经颅直流电刺激治疗3周后评估舌运动、口面失用及进食能力。利用脑电非线性分析观察1例吞咽失用症患者,经颅直流电刺激治疗前后安静闭眼、反射性和自主性吞咽状态下的大脑皮质电活动,记录6名健康者脑电图作为对照。结果:经皮电刺激配合手法训练后,患者吞咽能力均没有任何改善;经颅直流电刺激治疗后,患者自主性与无意识状态下舌运动均明显改善,口面失用评分由10分恢复到34—36分,均拔除鼻饲管。经颅直流电刺激治疗前,1例患者自主性吞咽时患侧中央、颞顶区皮质兴奋性明显低于反射性吞咽,经颅直流电刺激治疗后,自主性吞咽时脑区皮质兴奋性与反射性吞咽没有明显差异。结论:经颅直流电刺激为吞咽失用症提供了一种有效治疗手段,吞咽失用症的恢复可能与吞咽皮质兴奋性提高密切相关。     

经颅直流电刺激对脑卒中恢复期Broca失语患者图命名能力的影响

目的探讨经颅直流电刺激（tDCS）对脑卒中恢复期Broca失语患者图命名能力的影响。 方法选取5例左侧额叶或基底核区脑卒中恢复期Broca失语患者,采用自身对照方式,对患者分别进行左侧Broca区阳极、阴极、伪刺激tDCS,同时对患者进行图片命名检查,记录正确率,每次间隔时间≥24h。 结果在左侧Broca区实行tDCS阳极刺激、阴极刺激和伪刺激时,患者的图命名平均正确数分别为13.13、9.80和10.15。与阴极刺激和伪刺激下的平均正确数比较,左侧Broca区tDCS阳极刺激可以显著提高脑卒中恢复期Broca失语患者的图命名能力（P<0.05）。 结论左侧Broca区tDCS阳极刺激可显著改善脑卒中恢复期Broca失语症患者的图命名能力,其作用机制可能是tDCS阳极刺激增强了左侧Broca区皮质的兴奋性,提示左侧Broca区及其周围区对于脑卒中恢复期Broca失语症患者的语言恢复非常重要。     

重复经颅直流电刺激帕金森病模型大鼠的旋转行为

背景:经颅直流电刺激对帕金森病具有潜在的治疗作用,然而单次经颅直流电刺激的后效往往只能维持几个小时。目的:观察重复经颅直流电刺激对帕金森病大鼠旋转行为的治疗作用。方法:在SD大鼠黑质致密部和腹侧被盖区注射6-羟基多巴胺制作帕金森病大鼠模型,并完全随机分成阳极经颅直流电刺激组、阴极经颅直流电刺激组和对照组。对前两组大鼠初级运动区进行连续刺激10d,电流强度为80μA,刺激时间为30min/d的经颅直流电刺激。对照组不施加电刺激。结果与结论:重复阳极或阴极经颅直流电刺激对大鼠平均转速的减小存在显著的时间效应(P<0.05),刺激的后效可持续二三周;而对潜伏期和旋转持续时间改善作用不明显(P>0.05)。若保持两刺激组的刺激时间、刺激强度、刺激位置一致,则发现阴极经颅直流电刺激较阳极经颅直流电刺激对大鼠平均转速的减小更显著。结果提示使用重复经颅直流电刺激能够显著减小帕金森大鼠的旋转运动中的平均转速,且阴极刺激的效果更好。     

经颅磁刺激运动诱发电位有关指标及其在脑卒中运动功能评估中的应用研究进展

脑卒中是全球致残的最常见疾病,对患者功能障碍进行准确评定可更好的指导康复治疗并改善预后。大脑皮质兴奋性是脑卒中康复及预后的重要标志。然而目前临床评估多采用量表,精确性差,无法定量评定患者大脑兴奋性情况。由经颅磁刺激诱发的运动阈值及运动诱发电位是大脑皮质兴奋性的代表性评价指标,可定量评估大脑皮质兴奋性。近年来,经颅磁刺激成对脉冲刺激模式诱发的短间隔皮质内抑制及皮质内易化已成为皮质兴奋性相关研究的新方向。经颅磁刺激诱发的相关皮质兴奋性评价指标在脑卒中后运动功能评估及预后参考中有重要意义。本文就经颅磁刺激运动诱发电位有关指标的特性及其在脑卒中运动功能评估中的应用进行综述。     

重复经颅磁刺激治疗神经病理性疼痛研究进展

重复经颅磁刺激通过改变大脑皮质的兴奋性,改善脑血流和代谢,调节神经递质表达,改变神经系统可塑性,降低背根神经节内过度表达的神经元型一氧化氮合酶、抑制星形胶质细胞活性等途径,发挥治疗神经病理性疼痛的作用,目前已用于带状疱疹后神经痛、脑卒中后丘脑痛、脊髓损伤后神经痛、幻肢痛、三叉神经术后非典型面痛等的治疗中,疗效与刺激部位、频率、脉冲数、刺激器形状、刺激强度等因素有关。     

经皮脊髓直流电刺激的研究进展

经颅直流电刺激作为一种成熟的非侵袭性脑刺激技术取得了显著的临床效果。目前有学者将直流电刺激技术应用到脊髓上,发现经皮脊髓直流电刺激可影响脊髓传导束及脊髓环路的电活动,从而起到治疗慢性疼痛及改善运动功能的作用。本文介绍经皮脊髓直流电刺激的生物学效应、安全性及潜在的临床意义。     

经颅直流电刺激联合认知训练对脑损伤患者执行功能康复疗效的研究

目的:探讨经颅直流电刺激联合认知训练对脑损伤患者执行功能障碍的疗效。方法:选取脑损伤后执行功能障碍患者26例,采用随机数字表法将患者随机分为对照组(n=13)和试验组(n=13)。试验组患者在采用"认知康复工作站"进行常规认知康复训练的基础上,同时结合经颅直流电刺激仪器进行20min/次,1次/天,5天/周,持续6周的治疗。对照组患者进行常规的认知康复训练及假经颅直流电刺激治疗。对两组患者采用威斯康星卡片分类测验、Stroop测验、汉诺塔测验、数字倒背、额叶功能评定量表进行康复效果评定,分别在治疗前、治疗6周后及治疗结束后4周进行测试。结果:治疗前两组患者各项测试得分的差异无显著性意义(P>0.05)。对照组威斯康星卡片分类测验、汉诺塔测验、数字倒背及额叶功能评定量表的得分在治疗6周后较治疗前具有明显的提高,差异有显著性意义(P<0.05),但治疗结束后4周的测试结果较治疗前相比差异无显著性意义(P>0.05),说明治疗效果不能持续4周;试验组在治疗6周后除Stroop测验外其他测试均较治疗前成绩显著提高(P<0.01),且治疗结束后4周再次测试结果较治疗前仍具有显著性差异(P<0.01),说明经颅直流电刺激对执行功能障碍的改善效应至少可以持续4周。结论:经颅直流电刺激联合认知训练可以改善脑损伤患者执行功能,特别是在中远期的疗效方面更是优于传统的治疗方法。经颅直流电刺激作用持续,治疗过程安全、高效,在临床工作中具有广阔的应用前景。     

Non-invasive electric current stimulation for restoration of vision after unilateral occipital stroke

Occipital stroke often leads to visual field loss, for which no effective treatment exists. Little is known about the potential of non-invasive electric current stimulation to ameliorate visual functions in patients suffering from unilateral occipital stroke. One reason is the traditional thinking that visual field loss after brain lesions is permanent. Since evidence is available documenting vision restoration by means of vision training or non-invasive electric current stimulation future studies should also consider investigating recovery processes after visual cortical strokes. Here, protocols of repetitive transorbital alternating current stimulation (rtACS) and transcranial direct current stimulation (tDCS) are presented and the European consortium for restoration of vision (REVIS) is introduced. Within the consortium different stimulation approaches will be applied to patients with unilateral occipital strokes resulting in homonymous hemianopic visual field defects. The aim of the study is to evaluate effects of current stimulation of the brain on vision parameters, vision-related quality of life, and physiological parameters that allow concluding about the mechanisms of vision restoration. These include EEG-spectra and coherence measures, and visual evoked potentials. The design of stimulation protocols involves an appropriate sham-stimulation condition and sufficient follow-up periods to test whether the effects are stable.This is the first application of non-invasive current stimulation for vision rehabilitation in stroke-related visual field deficits. Positive results of the trials could have far-reaching implications for clinical practice. The ability of non-invasive electrical current brain stimulation to modulate the activity of neuronal networks may have implications for stroke rehabilitation also in the visual domain.     

Using non-invasive brain stimulation to augment motor training-induced plasticity

Therapies for motor recovery after stroke or traumatic brain injury are still not satisfactory. To date the best approach seems to be the intensive physical therapy. However the results are limited and functional gains are often minimal. The goal of motor training is to minimize functional disability and optimize functional motor recovery. This is thought to be achieved by modulation of plastic changes in the brain. Therefore, adjunct interventions that can augment the response of the motor system to the behavioural training might be useful to enhance the therapy-induced recovery in neurological populations. In this context, noninvasive brain stimulation appears to be an interesting option as an add-on intervention to standard physical therapies. Two non-invasive methods of inducing electrical currents into the brain have proved to be promising for inducing long-lasting plastic changes in motor systems: transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS). These techniques represent powerful methods for priming cortical excitability for a subsequent motor task, demand, or stimulation. Thus, their mutual use can optimize the plastic changes induced by motor practice, leading to more remarkable and outlasting clinical gains in rehabilitation. In this review we discuss how these techniques can enhance the effects of a behavioural intervention and the clinical evidence to date.     

Non-invasive brain stimulation (NIBS) and motor recovery after stroke

Recovery of motor function after stroke occurs largely on the basis of a sustained capacity of the adult brain for plastic changes. This brain plasticity has been validated by functional imaging and electrophysiological studies. Various concepts of how to enhance beneficial plasticity and in turn improve functional recovery are emerging based on the concept of functional interhemispheric balance between the two motor cortices. Besides conventional rehabilitation interventions and the most recent neuropharmacological approaches, non-invasive brain stimulation (NIBS) has recently been proposed as an add-on method to promote motor function recovery after stroke. Several methods can be used based either on transcranial magnetic stimulation (repetitive mode: rTMS, TBS) via a coil, or small electric current via larges electrodes placed on the scalp, (transcranial direct current stimulation tDCS). Depending on the different electrophysiological parameters of stimulation used, NIBS can induce a transient modulation of the excitability of the stimulated motor cortex (facilitation or inhibition) via a probable LTP-LTD-like mechanism. Several small studies have shown feasible and positive treatment effects for most of these strategies and their potential clinical relevance to help restoring the disruption of interhemispheric imbalance after stroke. Results of these studies are encouraging but many questions remain unsolved: what are the optimal stimulation parameters? What is the best NIBS intervention? Which cortex, injured or intact, should be stimulated? What is the best window of intervention? Is there a special subgroup of stroke patients who could strongly benefit from these interventions? Finally is it possible to boost NIBS treatment effect by motor training of the paretic hand or by additional neuropharmacological interventions? There is clearly a need for large-scale, controlled, multicenter trials to answer these questions before proposing their routine use in the management of stroke patients.     

Acute effects of bi-hemispheric transcranial direct current stimulation on the neuromuscular function of patients with chronic stroke: A randomized controlled study

BackgroundMuscle weakness in patients with chronic stroke is due to neuromuscular disorders such as muscle atrophy, loss of voluntary activation or weak muscle contractile properties which are majored by the imbalance of interhemispheric inhibition following stroke. In patients with chronic stroke, unilateral transcranial direct current stimulation improved the maximal isometric strength of paretic knee extensors, but bilateral transcranial direct current stimulation failed to improve concentric strength. This study aimed to assess if a bilateral current stimulation improves isometric maximal strength, voluntary activation and contractile properties of knee extensors in patients with chronic stroke.MethodsThirteen patients with chronic stroke and eight young healthy individuals participated in this randomized, simple-blinded, crossover study that included two experimental sessions: one with sham bilateral transcranial direct current stimulation and another with effective bilateral transcranial direct current stimulation (20 min, 2 mA). In the stroke patients, the anode was placed over the primary motor cortex of the affected hemisphere and the cathode over the contralateral primary motor cortex. In healthy participants, the brain side targeted by the anode and the cathode was randomly assigned. In each session, participants performed three assessments of strength, voluntary activation and contractile properties: before, during and after effective/sham bilateral transcranial direct current stimulation.FindingsBilateral transcranial direct current stimulation had no effect on any neuromuscular assessments in both groups (All P values > 0.05, partial eta-squares varied from 0.02 to 0.06).InterpretationA single session of bilateral transcranial direct current stimulation did not compensate muscular weakness of knee extensors in patients with chronic stroke.     

Non-invasive brain stimulation for the lower limb after stroke: what do we know so far and what should we be doing next?

Background: Non-invasive brain stimulation (NIBS) is promising as an adjuvant to rehabilitation of motor function after stroke. Despite numerous studies and reviews for the upper limb, NIBS targeting the lower limb and gait recovery after stroke is a newly emerging field of research. Purpose: To summarize findings from studies using NIBS to target the lower limb in stroke survivors. Methods: This narrative review describes studies of repetitive transcranial magnetic stimulation, paired associative stimulation and transcranial direct current stimulation with survivors of stroke. Results: NIBS appears capable of inducing changes in cortical excitability and lower limb function, but stimulation parameters and study designs vary considerably making it difficult to determine effectiveness. Conclusions: Future research should systematically assess differences in response with different stimulation parameters, test measures for determining who would be most likely to benefit and assess effectiveness with large samples before NIBS can be considered for use in clinical practice.

• Implications for Rehabilitation

• Stroke is a leading cause of disability, often resulting in dependency in activities of daily living and reduced quality of life.

• Non-invasive brain stimulation has received considerable interest as a potential adjuvant to rehabilitation after stroke and this review summarizes studies targeting the lower limb and gait recovery.

• Non-invasive brain stimulation can be used to modulate excitability of lower limb muscle representations and can lead to improvements in motor performance in stroke survivors.

• Non-invasive brain stimulation for gait recovery needs further investigation before translation to clinical practice is possible.

     

Effects of transcranial direct current stimulation (tDCS) on human regional cerebral blood flow

Transcranial direct current stimulation (tDCS) can up- and down-regulate cortical excitability depending on current direction, however our abilities to measure brain-tissue effects of the stimulation and its after-effects have been limited so far. We used regional cerebral blood flow (rCBF), a surrogate measure of brain activity, to examine regional brain-tissue and brain-network effects during and after tDCS. We varied the polarity (anodal and cathodal) as well as the current strength (0.8 to 2.0mA) of the stimulation. Fourteen healthy subjects were randomized into receiving either anodal or cathodal stimulation (two subjects received both, one week apart) while undergoing Arterial Spin Labeling (ASL) in the MRI scanner with an alternating off-on sampling paradigm. The stimulating, MRI-compatible electrode was placed over the right motor region and the reference electrode over the contralateral supra-orbital region. SPM5 was used to process and extract the rCBF data using a 10mm spherical volume of interest (VOI) placed in the motor cortex directly underneath the stimulating scalp electrode. Anodal stimulation induced a large increase (17.1%) in rCBF during stimulation, which returned to baseline after the current was turned off, but exhibited an increase in rCBF again in the post-stimulation period. Cathodal stimulation induced a smaller increase (5.6%) during stimulation, a significant decrease compared to baseline (-6.5%) after cessation, and a continued decrease in the post-stimulation period. These changes in rCBF were all significant when compared to the pre-stimulation baseline or to a control region. Furthermore, for anodal stimulation, there was a significant correlation between current strength and the increase in rCBF in the on-period relative to the pre-stimulation baseline. The differential rCBF after-effects of anodal (increase in resting state rCBF) and cathodal (decrease in resting state rCBF) tDCS support findings of behavioral and cognitive after-effects after cathodal and anodal tDCS. We also show that tDCS not only modulates activity in the brain region directly underlying the stimulating electrode but also in a network of brain regions that are functionally related to the stimulated area. Our results indicate that ASL may be an excellent tool to investigate the effects of tDCS and its stimulation parameters on brain activity.     

Transcranial direct current stimulation: a computer-based human model study

OBJECTIVES: Interest in transcranial direct current stimulation (tDCS) in clinical practice has been growing, however, the knowledge about its efficacy and mechanisms of action remains limited. This paper presents a realistic magnetic resonance imaging (MRI)-derived finite element model of currents applied to the human brain during tDCS. EXPERIMENTAL DESIGN: Current density distributions were analyzed in a healthy human head model with varied electrode montages. For each configuration, we calculated the cortical current density distributions. Analogous studies were completed for three pathological models of cortical infarcts. PRINCIPAL OBSERVATIONS: The current density magnitude maxima injected in the cortex by 1 mA tDCS ranged from 0.77 to 2.00 mA/cm(2). The pathological models revealed that cortical strokes, relative to the non-pathological solutions, can elevate current density maxima and alter their location. CONCLUSIONS: These results may guide optimized tDCS for application in normal subjects and patients with focal brain lesions.