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。     

Bilateral Occipital Lobe Infarction in Acute Migraine: Clinical, Neurophysiological, and Neuroradiological Study.

A woman having common migraine attacks coincident with an asymmetrical bilateral occipital lobe infarction that spared the brainstem and cerebellum underwent these studies: serial electroencephalography, brainstem auditory, visual and somatosensory evoked potentials, magnetic resonance imaging of the brain and cerebral arteriography. The patient's vision improved greatly during a one-year follow-up. The absence of risk factors for stroke suggested that migraine caused the infarction in the posterior circulation network. The pathophysiological mechanisms of stroke in migraine remains speculative.     

Neuroplastic changes following rehabilitative training correlate with regional electrical field induced with tDCS

Transcranial direct current stimulation (tDCS) has recently emerged as a promising approach to enhance neurorehabilitative outcomes. However, little is known about how the local electrical field generated by tDCS relates to underlying neuroplastic changes and behavior. To address this question, we present a case study analysis of an individual with hemianopia due to stroke and who benefited from a combined visual rehabilitation training and tDCS treatment program. Activation associated with a visual motion perception task (obtained by functional magnetic resonance imaging; fMRI) was used to characterize local changes in brain activity at baseline and after training. Individualized, high-resolution electrical field modeling reproducing precise cerebral and lesioned tissue geometry, predicted distortions of current flow in peri-lesional areas and diffuse clusters of peak electric fields. Using changes in fMRI signal as an index of cortical recovery, correlations to the electrical field map were determined. Significant correlations between the electrical field and change in fMRI signal were region specific including cortical areas under the anode electrode and peri-lesional visual areas. These patterns were consistent with effective tDCS facilitated rehabilitation. We describe the methodology used to analyze tDCS mechanisms through combined fMRI and computational modeling with the ultimate goal of developing a rationale for individualized therapy.     

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.     

Optic nerve atrophy and retinal nerve fibre layer thinning following optic neuritis: evidence that axonal loss is a substrate of MRI-detected atrophy

Magnetic resonance imaging (MRI) measures of brain atrophy are often considered to be a marker of axonal loss in multiple sclerosis (MS) but evidence is limited. Optic neuritis is a common manifestation of MS and results in optic nerve atrophy. Retinal nerve fibre layer (RNFL) imaging is a non-invasive way of detecting axonal loss following optic neuritis. We hypothesise that if the optic nerve atrophy that develops following optic neuritis is contributed to by axonal loss, it will correlate with thinning of the RNFL. Twenty-five patients were studied at least 1 year after a single unilateral attack of optic neuritis without recurrence, with a selection bias towards incomplete recovery. They had MR quantification of optic nerve cross-sectional area and optic nerve lesion length, as well as optical coherence tomography (OCT) measurement of mean RNFL thickness and macular volume, quantitative visual testing, and visual evoked potentials (VEPs). Fifteen controls were also studied. Significant optic nerve atrophy (mean decrease 30% versus controls), RNFL thinning (mean decrease 33% versus controls), and macular volume loss occurred in patients' affected eyes when compared with patients' unaffected eyes and healthy controls. The optic nerve atrophy was correlated with the RNFL thinning, macular volume loss, visual acuity, visual field mean deviation, and whole field VEP amplitude but not latency. These findings suggest that axonal loss contributes to optic nerve atrophy following a single attack of optic neuritis. By inference, axonal loss due to other post-inflammatory brain lesions is likely to contribute to the global MRI measure of brain atrophy in multiple sclerosis.     

CASE REPORT – EFFORT HEADACHE WITH CEREBRAL INFARCTION

SYNOPSIS
A 26 year old man ran a distance of 11/2 miles in 12 minutes. Soon after this effort he developed visual disturbances in the right field of vision and left-sided clumsiness associated with left frontal headache, nausea and vomiting. Four vessel arteriography and skull x-rays were normal but examination of the visual fields showed a right superior quadrantic field defect and the electroencephalogram a left posterior temporal slow focus. EMI scan performed a few days later showed an infarct in the left inferior occipital pole. No known risk factors for stroke were present. It is suggested that the cerebral infarction associated with headache was related to effort at altitude and most importantly to lack of physical training.     

TRANSIENT ABNORMALITY ON RADIONUCLIDE CEREBRAL DYNAMIC STUDY DURING A MIGRAINE ATTACK

SYNOPSIS
A 26 year old man ran a distance of 11/2 miles in 12 minutes. Soon after this effort he developed visual disturbances in the right field of vision and left-sided clumsiness associated with left frontal headache, nausea and vomiting. Four vessel arteriography and skull x-rays were normal but examination of the visual fields showed a right superior quadrantic field defect and the electroencephalogram a left posterior temporal slow focus. EMI scan performed a few days later showed an infarct in the left inferior occipital pole. No known risk factors for stroke were present. It is suggested that the cerebral infarction associated with headache was related to effort at altitude and most importantly to lack of physical training.     

Stroke. Risks, recognition, and return to work.

1. The two major classifications of stroke are ischemic and hemorrhagic. Ischemic strokes account for 75% of all strokes and result from the complete occlusion of an artery. Hemorrhagic strokes, often caused by aneurysm or hypertension, are caused by the rupture of a cerebral blood vessel and bleeding into the surrounding tissue. 2. The signs and symptoms of stroke may include unilateral weakness or paralysis, a sagging of one side of the face, double or blurred vision, vertigo, numbness or tingling, and language disturbances. 3. Management of ischemic stroke may include thrombolytic agents (e.g., heparin, warfarin) if the individual is treated within 6 hours after the onset of symptoms. Diagnostic tests may include, computed tomography scan, transesophageal echocardiagraphy, Doppler ultrasonography, and electrocordiography. 4. Occupational health nurses can be actively involved in helping workers modify their risks for stroke, developing and implementing an action plan if an individual is experiencing a stroke, and facilitating the individual's reentry into the worksite after rehabilitation is completed.     

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 treating neurogenic dysarthria: A systematic review

BackgroundAlthough non-invasive central and peripheral stimulations are accruing support as promising treatments in different neurological conditions, their effects on dysarthria have not been systematically investigated.ObjectiveThe purpose of this review was to examine the evidence base of non-invasive stimulation for treating dysarthria, identify which stimulation parameters have the most potential for treatment and determine safety risks.MethodsA systematic review with meta-analysis, when possible, involving publications indexed in MEDLINE, PsychINFO, EMBASE CINHAL the Linguistics and Language Behavioral Abstracts, Web of Science, Cochrane Register of Control Trials and 2 trial registries was completed. Articles were searched in December 2018 and updated in June 2021 using keywords related to brain and electrical stimulation, dysarthria and research design. We included trials with randomised, cross-over or quasi-experimental designs; involving a control group; and investigating treatment of neurogenic dysarthria with non-invasive stimulation. Methodological quality was determined with the Cochrane's Risk of Bias-2 tool.ResultsIn total, 6186 studies were identified; 10 studies (6 randomised controlled trials and 4 cross-over studies) fulfilled the inclusion criteria. All 10 trials (268 adults with Parkinson's disease, stroke and neurodegenerative cerebellar ataxia) focused on brain stimulation (6 repetitive transcranial magnetic stimulation; 3 transcranial direct current stimulation; and 1 repetitive transorbital alternating current stimulation). Adjunct speech-language therapy was delivered in 2 trials. Most trials reported one or more positive effects of stimulation on dysarthria-related features; however, given the overall high risk of bias and heterogeneity in participant, trial and outcome measurement characteristics, no conclusions can be drawn. Post-treatment size effects for 2 stroke trials demonstrated no statistically significant differences between active and sham stimulation across 3 dysarthria outcomes.ConclusionsEvidence for use of non-invasive brain stimulation in treating dysarthria remains inconclusive. Research trials that provide reliable and replicable findings are required.     

脑卒中患者执行功能的研究进展

执行功能障碍是脑卒中患者最为常见的认知功能障碍。除了经典范式的测量工具外,脑卒中患者执行功能的评定还有基于活动性能测试的方法。影响卒中后执行功能障碍因素有年龄、梗死区域和面积、心血管危险因素(高血压、糖尿病、房颤与吸烟)及受教育程度。除了传统的运动训练和认知康复外,非侵入性脑刺激技术(经颅直流电刺激和经颅磁刺激)、虚拟现实技术和抗抑郁药物治疗也逐渐用于改善卒中后执行功能障碍。     

Transcranial magnetic stimulation and stroke: a computer-based human model study

This paper explores how transcranial magnetic stimulation (TMS) induced currents in the brain are perturbed by electrical and anatomical changes following a stroke in its chronic stage. Multiple MRI derived finite element head models were constructed and evaluated to address the effects that strokes can have on the induced stimulating TMS currents by comparing stroke models of various sizes and geometries to a healthy head model under a number of stimulation conditions. The TMS induced currents were significantly altered for stimulation proximal to the lesion site in all of the models analyzed. The current density distributions were modified in magnitude, location, and orientation such that the population of neural elements that are stimulated will be correspondingly altered. The current perturbations were minimized for conditions tested where the coil was far removed from the lesion site, including models of stimulation contralateral to the lesioned hemisphere. The present limitations of TMS to the peri-lesional cortex are explored, ultimately concluding that conventional clinical standards for stimulation are unreliable and potentially dangerous predictors of the site and degree of stimulation when TMS is applied proximal to infarction site.     

Tc SPECT scan in a patient with occipital lobe infarction and complex visual hallucinations.

We have described a patient with occipital lobe infarction and CVH in the hemianopic field. Increased uptake in the right temporal lobe was documented on the brain Tc SPECT scan. We propose that activation of this area might be the underlying mechanism for visual hallucinations. This case report is a clear example of the wide spectrum of the clinical manifestations in stroke victims. We also emphasize the importance of educating the medical staff about the organic basis for human behavior.     

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1995/2011 PubMed 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.     

Cortical deactivation induced by visual stimulation in human slow-wave sleep

It has previously been demonstrated that sleeping and sedated young children respond with a paradoxical decrease in the blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) signal in the rostro-medial occipital visual cortex during visual stimulation. It is unresolved whether this negative BOLD response pattern is of developmental neurobiological origin particular to a given age or to a general effect of sleep or sedative drugs. To further elucidate this issue, we used fMRI and positron emission tomography (PET) to study the brain activation pattern during visual stimulation in spontaneously sleeping adult volunteers. In five sleeping volunteers fMRI studies confirmed a robust signal decrease during stimulation in the rostro-medial occipital cortex. A similar relative decrease at the same location was found during visual stimulation and polysomnographically verified slow-wave sleep in a separate group of six subjects using H(2)(15)O PET measures of the regional cerebral blood flow (rCBF). This decrease was more rostro-dorsal compared to the relative rCBF increase along the calcarine sulcus found during visual stimulation in the awake state. This study reconfirms the previously described paradoxical stimulation-correlated negative BOLD signal change in the rostro-medial occipital cortex, expanding this response mode to an age spectrum ranging from the newborn to the adult. Further, the use of complementary brain mapping techniques suggests that this decrease was secondary to a relative rCBF decrease. Possible mechanisms for the paradoxical response pattern during sleep include an active inhibition of the visual cortex or a disruption of an energy-consuming process.     

How early is early enough to prevent stroke in atrial fibrillation?

Atrial fibrillation (AF) is a potent risk factor for stroke, being responsible for 20% of ischemic strokes. Subclinical AF burden has received much attention, especially in the context of patients with cryptogenic strokes. However, little is known about the impact of subclinical episodes of rapid atrial rate and the primary risk of stroke and systemic embolism. Healey et al. investigated whether subclinical rapid atrial rate detected by implanted devices was associated with the risk of ischemic stroke in patients without clinical evidence of AF. The current article discusses the potential implications of the above results.     

Screening methods for post-stroke visual impairment: a systematic review

Purpose: To provide a systematic overview of the various tools available to screen for post-stroke visual impairment.

Methods: A review of the literature was conducted including randomised controlled trials, controlled trials, cohort studies, observational studies, systematic reviews and retrospective medical note reviews. All languages were included and translation was obtained. Participants included adults ≥18 years old diagnosed with a visual impairment as a direct cause of a stroke. We searched a broad range of scholarly online resources and hand-searched articles registers of published, unpublished and on-going trials. Search terms included a variety of MESH terms and alternatives in relation to stroke and visual conditions. Study selection was performed by two authors independently. The quality of the evidence and risk of bias were assessed using the STROBE, GRACE and PRISMA statements.

Results: A total of 25 articles (n?=?2924) were included in this review. Articles appraised reported on tools screening solely for visual impairments or for general post-stroke disabilities inclusive of vision. The majority of identified tools screen for visual perception including visual neglect (VN), with few screening for visual acuity (VA), visual field (VF) loss or ocular motility (OM) defects. Six articles reported on nine screening tools which combined visual screening assessment alongside screening for general stroke disabilities. Of these, three included screening for VA; three screened for VF loss; three screened for OM defects and all screened for VN. Two tools screened for all visual impairments. A further 19 articles were found which reported on individual vision screening tests in stroke populations; two for VF loss; 11 for VN and six for other visual perceptual defects. Most tools cannot accurately account for those with aphasia or communicative deficits, which are common problems following a stroke.

Conclusion: There is currently no standardised visual screening tool which can accurately assess all potential post-stroke visual impairments. The current tools screen for only a number of potential stroke-related impairments, which means many visual defects may be missed. The sensitivity of those which screen for all impairments is significantly lowered when patients are unable to report their visual symptoms. Future research is required to develop a tool capable of assessing stroke patients which encompasses all potential visual deficits and can also be easily performed by both the patients and administered by health care professionals in order to ensure all stroke survivors with visual impairment are accurately identified and managed.

• Implications for Rehabilitation

• Over 65% of stroke survivors will suffer from a visual impairment, whereas 45% of stroke units do not assess vision.

• Visual impairment significantly reduces the quality of life, such as being unable to return to work, driving and depression.

• This review outlines the available screening methods to accurately identify stroke survivors with visual impairments.

• Identifying visual impairment after stroke can aid general rehabilitation and thus, improve the quality of life for these patients.

     

低强度超声在脑神经疾病治疗中的应用研究进展

经颅直流电刺激,经颅磁刺激和深部脑刺激等神经调控技术已在多种神经/精神疾病(如帕金森,癫痫,抑郁症)的治疗中得到广泛应用,但仍存在直流电刺激深度浅、经颅磁刺激刺激精度受限等局限性。近年来,随着对超声波生物学效应的研究进展,低强度超声(SLIUS)经颅脑刺激这种新的神经调控治疗脑神经疾病的方法,因其具有无创、高空间分辨率以及高性价比等优点,而备受研究者青睐。LIUS主要通过非热效应发挥作用,在诸多脑神经疾病(如：创伤性颅脑损伤、缺血性脑卒中、阿尔茨海默病等)的治疗中取得了较大进展。现就该技术近年在脑神经疾病治疗中的主要研究进展及相关问题作一综述。     

A sham-controlled, phase II trial of transcranial direct current stimulation for the treatment of central pain in traumatic spinal cord injury

Past evidence has shown that motor cortical stimulation with invasive and non-invasive brain stimulation is effective to relieve central pain. Here we aimed to study the effects of another, very safe technique of non-invasive brain stimulation--transcranial direct current stimulation (tDCS)--on pain control in patients with central pain due to traumatic spinal cord injury. Patients were randomized to receive sham or active motor tDCS (2mA, 20 min for 5 consecutive days). A blinded evaluator rated the pain using the visual analogue scale for pain, Clinician Global Impression and Patient Global Assessment. Safety was assessed with a neuropsychological battery and confounders with the evaluation of depression and anxiety changes. There was a significant pain improvement after active anodal stimulation of the motor cortex, but not after sham stimulation. These results were not confounded by depression or anxiety changes. Furthermore, cognitive performance was not significantly changed throughout the trial in both treatment groups. The results of our study suggest that this new approach of cortical stimulation can be effective to control pain in patients with spinal cord lesion. We discuss potential mechanisms for pain amelioration after tDCS, such as a secondary modulation of thalamic nuclei activity.     

Differential effects of low-frequency rTMS at the occipital pole on visual-induced alpha desynchronization and visual-evoked potentials

Visual-induced alpha desynchronization (VID) and visual-evoked potentials (VEPs) characterize occipital activation in response to visual stimulation but their exact relationship is unclear. Here, we tested the hypothesis that VID and VEPs reflect different aspects of cortical activation. For this purpose, we determined whether VID and VEPs are differentially modulated by low-frequency repetitive transcranial magnetic stimulation (rTMS) over the occipital pole. Scalp EEG responses to visual stimuli (flashed either to the left or to the right visual field) were recorded for 8 min in six healthy subjects (1) before, (2) immediately following, and (3) 20 min after left occipital rTMS (1 Hz, 10 min). The parameters aimed to reduce cortical excitability beyond the end of the TMS train. In addition, simple reaction times to visual stimulation were recorded (left or right hand in separate blocks). In all subjects, VID was significantly and prominently reduced by rTMS (P = 0.0001). In contrast, rTMS failed to modulate early VEP components (P1/N1). A moderate effect was found on a late VEP component close to manual response onset (P = 0.014) but this effect was in the opposite direction to the VID change. All changes were restricted to the targeted left occipital cortex. The effects were present only after right visual field stimulation when a right hand response was required, were associated with a behavioral effect, and had washed out 20 min after rTMS. We conclude that VID and early VEPs represent different aspects of cortical activation. The findings that rTMS did not change early VEPs and selectively affected VID and late VEPs in conditions where the visual input must be transferred intrahemispherically for visuomotor integration (right visual field/right hand) are suggestive of rTMS interference with higher-order visual functions beyond visual input. This is consistent with the idea that alpha desynchronization serves an integrative role through a corticocortical "gating function."