Posts Tagged Noninvasive brain stimulation

[ARTICLE] Noninvasive Brain Stimulation to Enhance Functional Recovery After Stroke: Studies in Animal Models – Full Text

Background. Stroke is the leading cause of adult disability, but treatment options remain limited, leaving most patients with incomplete recovery. Patient and animal studies have shown potential of noninvasive brain stimulation (NIBS) strategies to improve function after stroke. However, mechanisms underlying therapeutic effects of NIBS are unclear and there is no consensus on which NIBS protocols are most effective.

Objective. Provide a review of articles that assessed effects and mechanisms of repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) in animal stroke models.

Methods. Articles were searched in PubMed, including cross-references.

Results. Nineteen eligible studies reporting effects of rTMS or tDCS after stroke in small rodents were identified. Seventeen of those described improved functional recovery or neuroprotection compared with untreated control or sham-stimulated groups. The effects of rTMS could be related to molecular mechanisms associated with ischemic tolerance, neuroprotection, anti-apoptosis, neurogenesis, angiogenesis, or neuroplasticity. Favorable outcome appeared most effectively when using high-frequency (>5 Hz) rTMS or intermittent theta burst stimulation of the ipsilesional hemisphere. tDCS effects were strongly dependent on stimulation polarity and onset time. Although these findings are promising, most studies did not meet Good Laboratory Practice assessment criteria.

Conclusions. Despite limited data availability, animal stroke model studies demonstrate potential of NIBS to promote stroke recovery through different working mechanisms. Future studies in animal stroke models should adhere to Good Laboratory Practice guidelines and aim to further develop clinically applicable treatment protocols by identifying most favorable stimulation parameters, treatment onset, adjuvant therapies, and underlying modes of action.

Globally, stroke is a devastating neurological disorder and a leading cause of death and acquired disability.1 The majority of stroke patients experience motor impairment, which affects movement of the face, leg, and/or arm on one side of the body.2 Upper limb motor deficiencies are often persistent and disabling, affecting independent functional activities of daily living.3 Unfortunately, most stroke patients recover incompletely after stroke, despite intensive rehabilitation strategies.3,4 Although there is a diverse range of interventions (for overview, see review by Pollock and colleagues4) aimed at improving motor outcome after stoke, there is still a pressing need for novel treatment therapies and continued research to reduce disability and improve functional recovery after stroke.

Noninvasive brain stimulation (NIBS) techniques, such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), have shown promising therapeutic potential in stroke patient studies.5,6 The rationale behind rTMS or tDCS therapy is to modulate cortical excitability, increase neural plasticity, and improve functional motor outcome. For many studies, this approach has been based on the interhemispheric competition model.7 The interhemispheric competition model suggests that functional recovery in stroke patients is hindered due to reduced output from the affected hemisphere and excessive transcallosal inhibition from the unaffected hemisphere.8 Therefore, improvement in motor deficits may be obtained with NIBS strategies that facilitate excitability in the affected hemisphere or suppress inhibitory activity from the unaffected hemisphere.9,10 Depending on the type and duration of the stimulation protocol, both rTMS and tDCS can be used to increase (>5 Hz rTMS; intermittent theta burst stimulation; anodal tDCS) or decrease (⩽1 Hz rTMS; continuous theta burst stimulation; cathodal tDCS) cortical excitability, with potentially lasting effects beyond the stimulation period, promoting mechanisms of synaptic plasticity.11 Evidence suggests that rTMS and tDCS techniques are able to induce changes in cortical excitability associated with facilitation or long-term potentiation like plasticity via glutamatergic neurotransmission, or inhibition and long-term depression via GABAergic neurotransmission.12,13 Furthermore, effects of rTMS and tDCS are not restricted to the target region of stimulation, but also affect distantly connected cortical areas, allowing for the modulation of large-scale neural networks.14

However, despite accumulating evidence of the potential of NIBS, the precise therapeutic mechanisms of action of rTMS and tDCS are largely unidentified and there is no consensus about standardized treatment protocols. Moreover, when deciding on treatment after stroke with either rTMS or tDCS, the poststroke time and lesion status should be considered, and stimulation intensity and duration must be fine-tuned to prevent further tissue damage or the interruption of beneficial plastic changes.15,16 These uncertainties emphasize the critical need for basic understanding of the (patho)physiological processes that are influenced by rTMS and tDCS paradigms after stroke, which may ideally be explored in well-controllable and reproducible experimental animal models.

In animal models of stroke, similar to the human condition, there is a variable degree of spontaneous functional improvement after stroke, associated with a complex cascade of cellular and molecular processes that are activated within minutes after the insult, both in perilesional tissue and remote brain regions.17,18 These events include changes in genetic transcriptional and translational processes, alterations in neurotransmitter interactions, altered secretion of growth factors, gliosis, vascular remodeling, and structural changes in axons, dendrites, and synapses.19,20 Therefore, assessment of the effects of NIBS on endogenous recovery processes in animal stroke models offer excellent opportunities for the exploration of neuroplastic and neuromodulatory mechanisms, which could aid in the optimization of treatment protocols for clinical applications.

Our goal was to provide an overview of studies that assessed functional outcomes and potential mechanisms of action of rTMS and tDCS in animal models of stroke, which may guide future studies that aim to improve mechanistic insights and therapeutic utilization of NIBS effects after stroke.[…]

 

Continue —->  Noninvasive Brain Stimulation to Enhance Functional Recovery After Stroke: Studies in Animal Models – Julia Boonzaier, Geralda A. F. van Tilborg, Sebastiaan F. W. Neggers, Rick M. Dijkhuizen, 2018

 

, , , , , , ,

Leave a comment

[Abstract] Effects of Electrical Stimulation in Tinnitus Patients: Conventional Versus High-Definition tDCS

Abstract

Background. Contradictory results have been reported for transcranial direct current stimulation (tDCS) as treatment for tinnitus. The recently developed high-definition tDCS (HD tDCS) uses smaller electrodes to limit the excitation to the desired brain areas.

Objective. The current study consisted of a retrospective part and a prospective part, aiming to compare 2 tDCS electrode placements and to explore effects of HD tDCS by matched pairs analyses.

Methods. Two groups of 39 patients received tDCS of the dorsolateral prefrontal cortex (DLPFC) or tDCS of the right supraorbital–left temporal area (RSO-LTA). Therapeutic effects were assessed with the tinnitus functional index (TFI), a visual analogue scale (VAS) for tinnitus loudness, and the hyperacusis questionnaire (HQ) filled out at 3 visits: pretherapy, posttherapy, and follow-up. With a new group of patients and in a similar way, the effects of HD tDCS of the right DLPFC were assessed, with the tinnitus questionnaire (TQ) and the hospital anxiety and depression scale (HADS) added.

Results. TFI total scores improved significantly after both tDCS and HD tDCS (DLPFC: P < .01; RSO-LTA: P < .01; HD tDCS: P = .05). In 32% of the patients, we observed a clinically significant improvement in TFI. The 2 tDCS groups and the HD tDCS group showed no differences on the evolution of outcomes over time (TFI: P = .16; HQ: P = .85; VAS: P = .20).

Conclusions. TDCS and HD tDCS resulted in a clinically significant improvement in TFI in 32% of the patients, with the 3 stimulation positions having similar results. Future research should focus on long-term effects of electrical stimulation.

via Effects of Electrical Stimulation in Tinnitus Patients: Conventional Versus High-Definition tDCS – Laure Jacquemin, Giriraj Singh Shekhawat, Paul Van de Heyning, Griet Mertens, Erik Fransen, Vincent Van Rompaey, Vedat Topsakal, Julie Moyaert, Jolien Beyers, Annick Gilles, 2018

, , , , , ,

Leave a comment

[Abstract] Transcranial Direct Current Stimulation Enhances Motor Skill Learning but Not Generalization in Chronic Stroke

Background. Motor training alone or combined with transcranial direct current stimulation (tDCS) positioned over the motor cortex (M1) improves motor function in chronic stroke. Currently, understanding of how tDCS influences the process of motor skill learning after stroke is lacking.

Objective. To assess the effects of tDCS on the stages of motor skill learning and on generalization to untrained motor function.

Methods. In this randomized, sham-controlled, blinded study of 56 mildly impaired chronic stroke patients, tDCS (anode over the ipsilesional M1 and cathode on the contralesional forehead) was applied during 5 days of training on an unfamiliar, challenging fine motor skill task (sequential visual isometric pinch force task). We assessed online and offline learning during the training period and retention over the following 4 months. We additionally assessed the generalization to untrained tasks.

Results. With training alone (sham tDCS group), patients acquired a novel motor skill. This skill improved online, remained stable during the offline periods and was largely retained at follow-up. When tDCS was added to training (real tDCS group), motor skill significantly increased relative to sham, mostly in the online stage. Long-term retention was not affected by tDCS. Training effects generalized to untrained tasks, but those performance gains were not enhanced further by tDCS.

Conclusions. Training of an unfamiliar skill task represents a strategy to improve fine motor function in chronic stroke. tDCS augments motor skill learning, but its additive effect is restricted to the trained skill.

 

via Transcranial Direct Current Stimulation Enhances Motor Skill Learning but Not Generalization in Chronic Stroke – Manuela Hamoudi, Heidi M. Schambra, Brita Fritsch, Annika Schoechlin-Marx, Cornelius Weiller, Leonardo G. Cohen, Janine Reis, 2018

, , , , , ,

Leave a comment

[Review] Transcranial Electrical Brain Stimulation – Full Text

Abstract

Transcranial electrical brain stimulation using weak direct current (tDCS) or alternating current (tACS) is being increasingly used in clinical and experimental settings to improve cognitive and motor functions in healthy subjects as well as neurological patients. This review focuses on the therapeutic value of transcranial direct current stimulation for neurorehabilitation and provides an overview of studies addressing motor and non-motor symptoms after stroke, disorders of attention and consciousness as well as Parkinson’s disease.

 

Background

The past 10 years have seen an increased clinical and experimental focus on noninvasive electrical brain stimulation as an innovative therapeutic approach to support neurorehabilitation. This entails the application of either transcranial direct current stimulation (tDCS), or less commonly, transcranial alternating current stimulation (tACS). Typically, up to 0.8 A/m² is used for up to 40 min per single stimulation session [1]. The electrical current partially penetrates the underlying structures and affects nerve cells, glia and vessels in the stimulated brain area [1] [2]. Early animal experiments during the 1960s and 1970s on the effects of weak DC stimulation demonstrated an excitement-induced change of neurons lasting several hours after the end of the stimulation [3] [4]. Therapeutic studies of the 1970s, at that time mainly concerning the treatment of depression, did not yield any success, which in retrospect could be attributed to the stimulation parameters used. In 2 000 key experiments by Nitsche and Paulus on polarity-related excitability changes in the human motor system after transcranial application of tDCS led to a renewed interest in the approach [5]. The authors documented increased cortical excitability measured by the amplitude of motor-evoked potentials in healthy volunteers after anodal stimulation above the motor cortex lasting at least 9 min [6]. Reversing the direction of stimulation (cathodal tDCS) resulted in a decrease in motor-evoked potential. In addition to the concept of pure excitability modulation, a large number of studies demonstrate modulation of neuroplasticity by tDCS in various ways, including basic scientific and mechanistic findings regarding improvement of synaptic transmission strength [7] [8] [9], long-term influence on learning processes and behavior [10] [11], as well as a therapeutic approach to improve function in neurological and psychiatric disorders associated with altered or disturbed neuroplasticity (overview in [12]). In particular, simultaneous application of tDCS together with different learning paradigms, such as motor or cognitive training, appears to produce favorable effects in healthy subjects and in various patient groups [11] [13].

The following review presents the effects of tDCS on the improvement in the function of some neurological disease patterns which are regularly the focus of neurorehabilitative treatment. This especially includes stroke. In addition, we shall refer to a current database of clinical studies containing a comprehensive list of scientific and clinical studies of tDCS in the treatment of neurological and psychiatric disorders [14].

Post-stroke Motor Impairment

Stroke is one of the primary causes worldwide of permanent limitations of motor function and speech. Despite intensive rehabilitation efforts, approx. 50% of stroke patients remain limited in their motor and speech capabilities [15] [16] [17]. Current understanding of the mechanisms of tDCS is largely based on data documented for the human motor system. The reasons for this include the presence of direct and easily objectifiable measurement criteria (for example, motor-evoked potential, fine motor function), as well as anatomical accessibility of brain motor regions for non-invasive stimulation. Therefore, it is not surprising that the clinical syndrome of stroke with the frequent symptom of hemiparesis as a “lesion model of the pyramidal tract” received significant scientific interest with respect to researching the effects of tDCS, as evidenced by the numerous scientific publications since 2005 ([Fig. 1]). In contrast to earlier largely mechanistic studies, in the past 5 years there has been a trend toward studies addressing clinically-oriented therapeutic issues. […]

Continue —> Thieme E-Journals – Neurology International Open / Full Text

Fig. 2 Illustration of the 3 typical brain stimulation montages exemplified by tDCS above the motor cortex. In example a, the anode (red) is placed above the ipsilesional motor cortex, and the cathode (blue) is located on the contralateral forehead. Example b shows the cathode placed above the motor cortex of the non-lesioned hemisphere, and the anode is placed on the contralateral forehead. Example c illustrates bihemispheric montage, with the anode located above the ipsilesional motor cortex, and the cathode placed above the motor cortex of the non-lesioned hemisphere. The white arrow shows the intracerebral current flow. The goal of these 3 arrangements is to modulate the interaction between both motor cortices by changing the activity of one or both hemispheres c.

, , , ,

Leave a comment

[Abstract] Importance and Difficulties of Pursuing rTMS Research in Acute Stroke

Abstract

Although much research has been done on repetitive transcranial magnetic stimulation (rTMS) in chronic stroke, only sparse research has been done in acute stroke despite the particularly rich potential for neuroplasticity in this stage.

We attempted a preliminary clinical trial in one active, high-quality inpatient rehabilitation facility (IRF) in the U.S. But after enrolling only four patients in the grant period, the study was stopped because of low enrollment.

The purpose of this paper is to offer a perspective describing the important physiologic rationale for including rTMS in the early phase of stroke, the reasons for our poor patient enrollment in our attempted study, and recommendations to help future studies succeed.

We conclude that, if scientists and clinicians hope to enhance stroke outcomes, more attention must be directed to leveraging conventional rehabilitation with neuromodulation in the acute phase of stroke when the capacity for neuroplasticity is optimal. Difficulties with patient enrollment must be addressed by reassessing traditional inclusion and exclusion criteria. Factors that shorten patients’ length of stay in the IRF must also be reassessed at all policy-making levels to make ethical decisions that promote higher functional outcomes while retaining cost consciousness.

Source: Importance and Difficulties of Pursuing rTMS Research in Acute Stroke | Physical Therapy | Oxford Academic

, , , , ,

Leave a comment

[Abstract] Evidence-based guidelines on the therapeutic use of transcranial direct current stimulation (tDCS) – Clinical Neurophysiology

Highlights

  • A group of European experts reviewed current evidence for therapeutic efficacy of tDCS.
  • Level B evidence (probable efficacy) was found for fibromyalgia, depression and craving.
  • The therapeutic relevance of tDCS needs to be further explored in these and other indications.

Abstract

A group of European experts was commissioned by the European Chapter of the International Federation of Clinical Neurophysiology to gather knowledge about the state of the art of the therapeutic use of transcranial direct current stimulation (tDCS) from studies published up until September 2016, regarding pain, Parkinson’s disease, other movement disorders, motor stroke, poststroke aphasia, multiple sclerosis, epilepsy, consciousness disorders, Alzheimer’s disease, tinnitus, depression, schizophrenia, and craving/addiction.

The evidence-based analysis included only studies based on repeated tDCS sessions with sham tDCS control procedure; 25 patients or more having received active treatment was required for Class I, while a lower number of 10–24 patients was accepted for Class II studies. Current evidence does not allow making any recommendation of Level A (definite efficacy) for any indication. Level B recommendation (probable efficacy) is proposed for: (i) anodal tDCS of the left primary motor cortex (M1) (with right orbitofrontal cathode) in fibromyalgia; (ii) anodal tDCS of the left dorsolateral prefrontal cortex (DLPFC) (with right orbitofrontal cathode) in major depressive episode without drug resistance; (iii) anodal tDCS of the right DLPFC (with left DLPFC cathode) in addiction/craving. Level C recommendation (possible efficacy) is proposed for anodal tDCS of the left M1 (or contralateral to pain side, with right orbitofrontal cathode) in chronic lower limb neuropathic pain secondary to spinal cord lesion. Conversely, Level B recommendation (probable inefficacy) is conferred on the absence of clinical effects of: (i) anodal tDCS of the left temporal cortex (with right orbitofrontal cathode) in tinnitus; (ii) anodal tDCS of the left DLPFC (with right orbitofrontal cathode) in drug-resistant major depressive episode.

It remains to be clarified whether the probable or possible therapeutic effects of tDCS are clinically meaningful and how to optimally perform tDCS in a therapeutic setting. In addition, the easy management and low cost of tDCS devices allow at home use by the patient, but this might raise ethical and legal concerns with regard to potential misuse or overuse. We must be careful to avoid inappropriate applications of this technique by ensuring rigorous training of the professionals and education of the patients.

Source: Evidence-based guidelines on the therapeutic use of transcranial direct current stimulation (tDCS) – Clinical Neurophysiology

, , , , , , ,

Leave a comment

[BOOK] Rehabilitation Strategies for Restorative Approaches After Stroke and Neurotrauma – Springer

Abstract

For acute, subacute, or chronic stroke, and neurotrauma, a range of rehabilitation strategies will be essential to optimize possible benefits of molecular, cellular, and novel pharmacological restorative approaches. The neurorehabilitation strategies must be chosen to engage the targeted networks of these novel approaches, drawing upon studies of motor and cognitive learning-related neural adaptations that accompany progressive practice. Regulatory agencies and the pharma/biotech industry will need to keep an open mind about the likely synergy that will come from interleaving repair strategies and rehabilitation interventions.

For clinical trials aimed at motor restoration, outcome measurement tools should be relevant to the anticipated targets of repair-enhanced rehabilitation. Most outcomes to date have been drawn from disease-specific and rehabilitation toolboxes. In studies that include participants who are more than a few weeks beyond acquiring profound impairments and disabilities, outcome measures will likely have to go beyond off-the-shelf tools that were not designed to detect modest clinical evidence of sensorimotor system repair. This chapter describes specific rehabilitation strategies and outcome assessments in the context of interfacing them with neurorestoration approaches.

, , , , , , , , ,

Leave a comment

[ ARTICLE] Neuroplasticity in post-stroke gait recovery and noninvasive brain stimulation – Full Text PDF

Abstract

Gait disorders drastically affect the quality of life of stroke survivors, making post-stroke rehabilitation an important research focus. Noninvasive brain stimulation has potential in facilitating neuroplasticity and improving post-stroke gait impairment. However, a large inter-individual variability in the response to noninvasive brain stimulation interventions has been increasingly recognized. We first review the neurophysiology of human gait and post-stroke neuroplasticity for gait recovery, and then discuss how noninvasive brain stimulation techniques could be utilized to enhance gait recovery. While post-stroke neuroplasticity for gait recovery is characterized by use-dependent plasticity, it evolves over time, is idiosyncratic, and may develop maladaptive elements. Furthermore, noninvasive brain stimulation has limited reach capability and is facilitative-only in nature. Therefore, we recommend that noninvasive brain stimulation be used adjunctively with rehabilitation training and other concurrent neuroplasticity facilitation techniques. Additionally, when noninvasive brain stimulation is applied for the rehabilitation of gait impairment in stroke survivors, stimulation montages should be customized according to the specific types of neuroplasticity found in each individual. This could be done using multiple mapping techniques.

Introduction

The American Heart Association estimates that approximately 795,000 individuals in the United States have a stroke each year (Go et al., 2014). A lack of mobility is the main obstacle for stroke survivors seeking to regain daily living independence and social integration. Thus, restoring impaired gait is one of the major goals of post-stroke rehabilitation. Recently, traditional rehabilitation techniques have been augmented by the use of a new methodology, noninvasive brain stimulation (NIBS), which facilitates neuroplasticity. To better understand the use of NIBS, this paper reviews literature regarding the neurophysiology of human gait, poststroke neuroplasticity in the motor control system underlying gait, and finally, approaches for using NIBS to enhance gait recovery.

Neurophysiology of Human Gait

Involvement of the cerebral cortices: In functional neuroimaging studies of human walking, the premotor cortex (PMC) and the supplementary motor cortex (SMC) are activated prior to step onset (Huppert et al., 2013). However, lesions in these two areas often lead to problems with gait initiation and the negotiation of narrow passages (Jahn et al., 2004), indicating their importance in the initiation and planning of walking. Furthermore, corticospinal inputs significantly facilitate muscular responses in the lower limbs, especially during the swing phase of the step cycle (Pijnappels et al., 1998). These observations suggest that cortical outputs play a critical role in the modulation of lower limb locomotion…

Full Text PDF

 

 

 

, , , , , , , , , , , , , , ,

Leave a comment

[ARTICLE] Rehabilitation with Poststroke Motor Recovery: A Review with a Focus on Neural Plasticity – Full Text HTML

Abstract

Motor recovery after stroke is related to neural plasticity, which involves developing new neuronal interconnections, acquiring new functions, and compensating for impairment. However, neural plasticity is impaired in the stroke-affected hemisphere. Therefore, it is important that motor recovery therapies facilitate neural plasticity to compensate for functional loss. Stroke rehabilitation programs should include meaningful, repetitive, intensive, and task-specific movement training in an enriched environment to promote neural plasticity and motor recovery. Various novel stroke rehabilitation techniques for motor recovery have been developed based on basic science and clinical studies of neural plasticity. However, the effectiveness of rehabilitative interventions among patients with stroke varies widely because the mechanisms underlying motor recovery are heterogeneous. Neurophysiological and neuroimaging studies have been developed to evaluate the heterogeneity of mechanisms underlying motor recovery for effective rehabilitation interventions after stroke. Here, we review novel stroke rehabilitation techniques associated with neural plasticity and discuss individualized strategies to identify appropriate therapeutic goals, prevent maladaptive plasticity, and maximize functional gain in patients with stroke.

Continue —> Rehabilitation with Poststroke Motor Recovery: A Review with a Focus on Neural Plasticity.

, , , , , , , , , , , , , , , ,

Leave a comment

[ARTICLE] Noninvasive Neuromodulation in Poststroke Gait Disorders

Abstract

Walking rehabilitation is one of the primary goals in stroke survivors because of its great potential for recovery and its functional relevance in daily living activities. Although 70% to 80% of people in the chronic poststroke phases are able to walk, impairment of gait often persists, involving speed, endurance, and stability.

Walking involves several brain regions, such as the sensorimotor cortex, supplementary motor area, cerebellum, and brainstem, which are approachable by the application of noninvasive brain stimulation (NIBS). NIBS techniques, such as repetitive transcranial magnetic stimulation and transcranial direct current stimulation, have been reported to modulate neural activity beyond the period of stimulation, facilitating neuroplasticity. NIBS methods have been largely applied for improving paretic hand motor function and stroke-associated cognitive deficits. Recent studies suggest a possible effectiveness of these techniques also in the recovery of poststroke gait disturbance. This article is a selective review about functional investigations addressing the mechanisms of lower-limb motor system reorganization after stroke and the application of NIBS for neurorehabilitation.

via Noninvasive Neuromodulation in Poststroke Gait Disorders.

 

, , , , , ,

Leave a comment

%d bloggers like this: