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Charvet L, Harrison AT, Mangold K, Moore RD, Guo S, Zhang J, Datta A, Androulakis XM. Remotely supervised at-home tDCS for veterans with persistent post-traumatic headache: a double-blind, sham-controlled randomized pilot clinical trial. Front Neurol 2023; 14:1184056. [PMID: 37213913 PMCID: PMC10196360 DOI: 10.3389/fneur.2023.1184056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 04/14/2023] [Indexed: 05/23/2023] Open
Abstract
Background Currently, there are no FDA approved therapies for persistent post-traumatic headache (PPTH) secondary to traumatic brain injury (TBI). As such neither headache nor TBI specialists have an effective means to manage PPTH. Thus, the objective of the present pilot trial was to evaluate the feasibility and preliminary efficacy of a four-week at-home remotely supervised transcranial direct current stimulation (RS-tDCS) intervention for veterans with PPTH. Methods Twenty-five (m = 46.6 ± 8.7 years) veterans with PPTH were randomized into two groups and received either active (n = 12) or sham (n = 13) RS-tDCS, with anodal stimulation over left dlPFC and cathodal over occipital pole. Following a four-week baseline, participants completed 20-sessions of active or sham RS-tDCS with real-time video monitoring over a period of four-weeks. Participants were assessed again at the end of the intervention and at four-weeks post-intervention. Primary outcomes were overall adherence rate (feasibility) and change in moderate-to-severe headache days per month (efficacy). Secondary outcomes were changes in total number of headache days, and PPTH-related functional outcomes. Results Adherence rate was high with 88% of participants (active = 10/12; sham = 12/13) fully completing tDCS interventions. Importantly, there was no significant difference in adherence between active and sham groups (p = 0.59). Moderate-to-severe headache days were significantly reduced within the active RS-tDCS group (p = 0.004), compared to sham during treatment (-2.5 ± 3.5 vs. 2.3 ± 3.4), and 4-week follow-up (-3.9 ± 6.4 vs. 1.2 ± 6.5). Total number of headache days was significantly reduced within the active RS-tDCS (p = 0.03), compared to sham during-treatment (-4.0 ± 5.2 vs. 1.5 ± 3.8), and 4-week follow-up (-2.1 ± 7.2 vs. -0.2 ± 4.4). Conclusion The current results indicate our RS-tDCS paradigm provides a safe and effective means for reducing the severity and number of headache days in veterans with PPTH. High treatment adherence rate and the remote nature of our paradigm indicate RS-tDCS may be a feasible means to reduce PPTH, especially for veterans with limited access to medical facilities.Clinical Trial Registration: ClinicalTrials.gov, identifier [NCT04012853].
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Affiliation(s)
- Leigh Charvet
- Department of Neurology, New York University Langone Health, New York, NY, United States
| | - Adam T. Harrison
- Arnold School of Public Health, University of South Carolina, Columbia, SC, United States
- Department of Neurology, Columbia VA Healthcare System, Columbia, SC, United States
| | - Kiersten Mangold
- Arnold School of Public Health, University of South Carolina, Columbia, SC, United States
- Department of Neurology, Columbia VA Healthcare System, Columbia, SC, United States
| | - Robert Davis Moore
- Arnold School of Public Health, University of South Carolina, Columbia, SC, United States
| | - Siyuan Guo
- Department of Biostatistics & Bioinformatics, Duke University School of Medicine, Durham, NC, United States
| | - Jiajia Zhang
- Arnold School of Public Health, University of South Carolina, Columbia, SC, United States
| | - Abhishek Datta
- Research and Development, Soterix Medical, Inc., Woodbridge, NJ, United States
- Department of Biomedical Engineering, City College of New York, New York, NY, United States
| | - X. Michelle Androulakis
- Department of Neurology, Columbia VA Healthcare System, Columbia, SC, United States
- Headache Centers of Excellence Program, US Department of Veterans Affairs, Columbia, SC, United States
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Linnhoff S, Koehler L, Haghikia A, Zaehle T. The therapeutic potential of non-invasive brain stimulation for the treatment of Long-COVID-related cognitive fatigue. Front Immunol 2023; 13:935614. [PMID: 36700201 PMCID: PMC9869163 DOI: 10.3389/fimmu.2022.935614] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 12/19/2022] [Indexed: 01/11/2023] Open
Abstract
Following an acute COVID-19 infection, a large number of patients experience persisting symptoms for more than four weeks, a condition now classified as Long-COVID syndrome. Interestingly, the likelihood and severity of Long-COVID symptoms do not appear to be related to the severity of the acute COVID-19 infection. Fatigue is amongst the most common and debilitating symptoms of Long-COVID. Other symptomes include dyspnoea, chest pain, olfactory disturbances, and brain fog. Fatigue is also frequently reported in many other neurological diseases, affecting a broad range of everyday activities. However, despite its clinical significance, limited progress has been made in understanding its causes and developing effective treatment options. Non-invasive brain stimulation (NIBS) methods offer the unique opportunity to modulate fatigue-related maladaptive neuronal activity. Recent data show promising results of NIBS applications over frontoparietal regions to reduce fatigue symptoms. In this current paper, we review recent data on Long-COVID and Long-COVID-related fatigue (LCOF), with a special focus on cognitive fatigue. We further present widely used NIBS methods, such as transcranial direct current stimulation, transcranial alternating current stimulation, and transcutaneous vagus nerve stimulation and propose their use as possible therapeutic strategies to alleviate individual pathomechanisms of LCOF. Since NIBS methods are safe and well-tolerated, they have the potential to enhance the quality of life in a broad group of patients.
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Affiliation(s)
- Stefanie Linnhoff
- Department of Neurology, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany
| | - Lilli Koehler
- Department of Neurology, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany
| | - Aiden Haghikia
- Department of Neurology, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany,Center for Behavioral Brain Sciences (CBBS), Magdeburg, Germany
| | - Tino Zaehle
- Department of Neurology, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany,Center for Behavioral Brain Sciences (CBBS), Magdeburg, Germany,*Correspondence: Tino Zaehle,
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Arora Y, Dutta A. Human-in-the-Loop Optimization of Transcranial Electrical Stimulation at the Point of Care: A Computational Perspective. Brain Sci 2022; 12:brainsci12101294. [PMID: 36291228 PMCID: PMC9599464 DOI: 10.3390/brainsci12101294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 09/05/2022] [Accepted: 09/18/2022] [Indexed: 11/17/2022] Open
Abstract
Individual differences in the responsiveness of the brain to transcranial electrical stimulation (tES) are increasingly demonstrated by the large variability in the effects of tES. Anatomically detailed computational brain models have been developed to address this variability; however, static brain models are not “realistic” in accounting for the dynamic state of the brain. Therefore, human-in-the-loop optimization at the point of care is proposed in this perspective article based on systems analysis of the neurovascular effects of tES. First, modal analysis was conducted using a physiologically detailed neurovascular model that found stable modes in the 0 Hz to 0.05 Hz range for the pathway for vessel response through the smooth muscle cells, measured with functional near-infrared spectroscopy (fNIRS). During tES, the transient sensations can have arousal effects on the hemodynamics, so we present a healthy case series for black-box modeling of fNIRS−pupillometry of short-duration tDCS effects. The block exogeneity test rejected the claim that tDCS is not a one-step Granger cause of the fNIRS total hemoglobin changes (HbT) and pupil dilation changes (p < 0.05). Moreover, grey-box modeling using fNIRS of the tDCS effects in chronic stroke showed the HbT response to be significantly different (paired-samples t-test, p < 0.05) between the ipsilesional and contralesional hemispheres for primary motor cortex tDCS and cerebellar tDCS, which was subserved by the smooth muscle cells. Here, our opinion is that various physiological pathways subserving the effects of tES can lead to state−trait variability, which can be challenging for clinical translation. Therefore, we conducted a case study on human-in-the-loop optimization using our reduced-dimensions model and a stochastic, derivative-free covariance matrix adaptation evolution strategy. We conclude from our computational analysis that human-in-the-loop optimization of the effects of tES at the point of care merits investigation in future studies for reducing inter-subject and intra-subject variability in neuromodulation.
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Affiliation(s)
- Yashika Arora
- Neuroimaging and Neurospectroscopy Lab, National Brain Research Centre, Gurgaon 122052, India
| | - Anirban Dutta
- Neuroengineering and Informatics for Rehabilitation and Simulation-Based Learning (NIRSlearn), University of Lincoln, Lincoln LN6 7TS, UK
- Correspondence:
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Kricheldorff J, Göke K, Kiebs M, Kasten FH, Herrmann CS, Witt K, Hurlemann R. Evidence of Neuroplastic Changes after Transcranial Magnetic, Electric, and Deep Brain Stimulation. Brain Sci 2022; 12:929. [PMID: 35884734 PMCID: PMC9313265 DOI: 10.3390/brainsci12070929] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Revised: 07/06/2022] [Accepted: 07/08/2022] [Indexed: 02/04/2023] Open
Abstract
Electric and magnetic stimulation of the human brain can be used to excite or inhibit neurons. Numerous methods have been designed over the years for this purpose with various advantages and disadvantages that are the topic of this review. Deep brain stimulation (DBS) is the most direct and focal application of electric impulses to brain tissue. Electrodes are placed in the brain in order to modulate neural activity and to correct parameters of pathological oscillation in brain circuits such as their amplitude or frequency. Transcranial magnetic stimulation (TMS) is a non-invasive alternative with the stimulator generating a magnetic field in a coil over the scalp that induces an electric field in the brain which, in turn, interacts with ongoing brain activity. Depending upon stimulation parameters, excitation and inhibition can be achieved. Transcranial electric stimulation (tES) applies electric fields to the scalp that spread along the skull in order to reach the brain, thus, limiting current strength to avoid skin sensations and cranial muscle pain. Therefore, tES can only modulate brain activity and is considered subthreshold, i.e., it does not directly elicit neuronal action potentials. In this review, we collect hints for neuroplastic changes such as modulation of behavior, the electric activity of the brain, or the evolution of clinical signs and symptoms in response to stimulation. Possible mechanisms are discussed, and future paradigms are suggested.
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Affiliation(s)
- Julius Kricheldorff
- Department of Neurology, School of Medicine and Health Sciences, Carl von Ossietzky University, 26129 Oldenburg, Germany; (J.K.); (K.W.)
| | - Katharina Göke
- Division of Medical Psychology, Department of Psychiatry and Psychotherapy, University Hospital Bonn, 53127 Bonn, Germany; (K.G.); (M.K.)
- Institute of Medical Science, University of Toronto, Toronto, ON M5S 3G8, Canada
| | - Maximilian Kiebs
- Division of Medical Psychology, Department of Psychiatry and Psychotherapy, University Hospital Bonn, 53127 Bonn, Germany; (K.G.); (M.K.)
| | - Florian H. Kasten
- Experimental Psychology Lab, Carl von Ossietzky University, 26129 Oldenburg, Germany; (F.H.K.); (C.S.H.)
| | - Christoph S. Herrmann
- Experimental Psychology Lab, Carl von Ossietzky University, 26129 Oldenburg, Germany; (F.H.K.); (C.S.H.)
- Research Center Neurosensory Sciences, Carl von Ossietzky University, 26129 Oldenburg, Germany
| | - Karsten Witt
- Department of Neurology, School of Medicine and Health Sciences, Carl von Ossietzky University, 26129 Oldenburg, Germany; (J.K.); (K.W.)
- Research Center Neurosensory Sciences, Carl von Ossietzky University, 26129 Oldenburg, Germany
| | - Rene Hurlemann
- Division of Medical Psychology, Department of Psychiatry and Psychotherapy, University Hospital Bonn, 53127 Bonn, Germany; (K.G.); (M.K.)
- Research Center Neurosensory Sciences, Carl von Ossietzky University, 26129 Oldenburg, Germany
- Department of Psychiatry and Psychotherapy, Carl von Ossietzky University, 26129 Oldenburg, Germany
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Mizutani-Tiebel Y, Takahashi S, Karali T, Mezger E, Bulubas L, Papazova I, Dechantsreiter E, Stoecklein S, Papazov B, Thielscher A, Padberg F, Keeser D. Differences in electric field strength between clinical and non-clinical populations induced by prefrontal tDCS: A cross-diagnostic, individual MRI-based modeling study. Neuroimage Clin 2022; 34:103011. [PMID: 35487132 PMCID: PMC9125784 DOI: 10.1016/j.nicl.2022.103011] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 03/17/2022] [Accepted: 04/13/2022] [Indexed: 01/25/2023]
Abstract
MDD and SCZ showed lower prefrontal tDCS-induced e-field strengths compared to HC. Average e-field strengths did not significantly differ between MDD and SCZ patients. Inter-individual variability of e-field intensities and distribution was prominent. Inter-rater variability emphasizes the importance of standardized positioning.
Introduction Prefrontal cortex (PFC) regions are promising targets for therapeutic applications of non-invasive brain stimulation, e.g. transcranial direct current stimulation (tDCS), which has been proposed as a novel intervention for major depressive disorder (MDD) and negative symptoms of schizophrenia (SCZ). However, the effects of tDCS vary inter-individually, and dose–response relationships have not been established. Stimulation parameters are often tested in healthy subjects and transferred to clinical populations. The current study investigates the variability of individual MRI-based electric fields (e-fields) of standard bifrontal tDCS across individual subjects and diagnoses. Method The study included 74 subjects, i.e. 25 patients with MDD, 24 patients with SCZ, and 25 healthy controls (HC). Individual e-fields of a common tDCS protocol (i.e. 2 mA stimulation intensity, bifrontal anode-F3/cathode-F4 montage) were modeled by two investigators using SimNIBS (2.0.1) based on structural MRI scans. Result On a whole-brain level, the average e-field strength was significantly reduced in MDD and SCZ compared to HC, but MDD and SCZ did not differ significantly. Regions of interest (ROI) analysis for PFC subregions showed reduced e-fields in Sallet areas 8B and 9 for MDD and SCZ compared to HC, whereas there was again no difference between MDD and SCZ. Within groups, we generally observed high inter-individual variability of e-field intensities at a higher percentile of voxels. Conclusion MRI-based e-field modeling revealed significant differences in e-field strengths between clinical and non-clinical populations in addition to a general inter-individual variability. These findings support the notion that dose–response relationships for tDCS cannot be simply transferred from healthy to clinical cohorts and need to be individually established for clinical groups. In this respect, MRI-based e-field modeling may serve as a proxy for individualized dosing.
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Affiliation(s)
- Yuki Mizutani-Tiebel
- Department of Psychiatry and Psychotherapy, University Hospital LMU, Munich, Germany; NeuroImaging Core Unit Munich (NICUM), Munich, Germany.
| | - Shun Takahashi
- Department of Psychiatry and Psychotherapy, University Hospital LMU, Munich, Germany; Department of Neuropsychiatry, Wakayama Medical University, Wakayama, Japan; Clinical Research and Education Center, Asakayama General Hospital, Sakai, Japan; Graduate School of Rehabilitation Science, Osaka Metropolitan University, Habikino, Japan; Department of Psychiatry, Osaka University Graduate School of Medicine, Suita, Japan
| | - Temmuz Karali
- Department of Psychiatry and Psychotherapy, University Hospital LMU, Munich, Germany; Department of Radiology, University Hospital LMU, Munich, Germany
| | - Eva Mezger
- Department of Psychiatry and Psychotherapy, University Hospital LMU, Munich, Germany
| | - Lucia Bulubas
- Department of Psychiatry and Psychotherapy, University Hospital LMU, Munich, Germany; International Max Planck Research School for Translational Psychiatry (IMPRS-TP), Munich, Germany
| | - Irina Papazova
- Department of Psychiatry and Psychotherapy, University Hospital LMU, Munich, Germany; Department of Psychiatry and Psychotherapy, University of Augsburg, Germany
| | - Esther Dechantsreiter
- Department of Psychiatry and Psychotherapy, University Hospital LMU, Munich, Germany
| | | | - Boris Papazov
- NeuroImaging Core Unit Munich (NICUM), Munich, Germany; Department of Radiology, University Hospital LMU, Munich, Germany
| | - Axel Thielscher
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark; Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Frank Padberg
- Department of Psychiatry and Psychotherapy, University Hospital LMU, Munich, Germany
| | - Daniel Keeser
- Department of Psychiatry and Psychotherapy, University Hospital LMU, Munich, Germany; NeuroImaging Core Unit Munich (NICUM), Munich, Germany; Department of Radiology, University Hospital LMU, Munich, Germany; Munich Center for Neurosciences (MCN) - Brain & Mind, 82152 Planegg-Martinsried, Germany.
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Ayache SS, Serratrice N, Abi Lahoud GN, Chalah MA. Fatigue in Multiple Sclerosis: A Review of the Exploratory and Therapeutic Potential of Non-Invasive Brain Stimulation. Front Neurol 2022; 13:813965. [PMID: 35572947 PMCID: PMC9101483 DOI: 10.3389/fneur.2022.813965] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 03/28/2022] [Indexed: 11/29/2022] Open
Abstract
Fatigue is the most commonly reported symptom in patients with multiple sclerosis (MS). It is a worrisome, frequent, and debilitating manifestation that could occur at any time during the course of MS and in all its subtypes. It could engender professional, familial, and socioeconomic consequences and could severely compromise the patients' quality of life. Clinically, the symptom exhibits motor, cognitive, and psychosocial facets. It is also important to differentiate between perceived or subjective self-reported fatigue and fatigability which is an objective measure of decrement in the performance of cognitive or motor tasks. The pathophysiology of MS fatigue is complex, and its management remains a challenge, despite the existing body of literature on this matter. Hence, unraveling its neural mechanisms and developing treatment options that target the latter might constitute a promising field to explore. A PubMed/Medline/Scopus search was conducted to perform this review which aims (a) to reappraise the available electrophysiological studies that explored fatigue in patients with MS with a particular focus on corticospinal excitability measures obtained using transcranial magnetic stimulation and (b) to assess the potential utility of employing neuromodulation (i.e., non-invasive brain stimulation techniques) in this context. A special focus will be put on the role of transcranial direct current stimulation and transcranial magnetic stimulation. We have provided some suggestions that will help overcome the current limitations in upcoming research.
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Affiliation(s)
- Samar S. Ayache
- EA4391 Excitabilité Nerveuse and Thérapeutique, Université Paris Est Créteil, Créteil, France
- Department of Clinical Neurophysiology, DMU FIxIT, Henri Mondor University Hospital, Assistance Publique-Hôpitaux de Paris (APHP), Créteil, France
- *Correspondence: Samar S. Ayache
| | - Nicolas Serratrice
- Department of Spine Surgery, Centre Médico Chirurgical Bizet, Paris, France
- Institut de la Colonne Vertébrale et des Neurosciences (ICVNS), Centre Médico Chirurgical Bizet, Paris, France
| | - Georges N. Abi Lahoud
- Department of Spine Surgery, Centre Médico Chirurgical Bizet, Paris, France
- Institut de la Colonne Vertébrale et des Neurosciences (ICVNS), Centre Médico Chirurgical Bizet, Paris, France
| | - Moussa A. Chalah
- EA4391 Excitabilité Nerveuse and Thérapeutique, Université Paris Est Créteil, Créteil, France
- Department of Clinical Neurophysiology, DMU FIxIT, Henri Mondor University Hospital, Assistance Publique-Hôpitaux de Paris (APHP), Créteil, France
- Moussa A. Chalah
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Grey-box modeling and hypothesis testing of functional near-infrared spectroscopy-based cerebrovascular reactivity to anodal high-definition tDCS in healthy humans. PLoS Comput Biol 2021; 17:e1009386. [PMID: 34613970 PMCID: PMC8494321 DOI: 10.1371/journal.pcbi.1009386] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 08/28/2021] [Indexed: 12/12/2022] Open
Abstract
Transcranial direct current stimulation (tDCS) has been shown to evoke hemodynamics response; however, the mechanisms have not been investigated systematically using systems biology approaches. Our study presents a grey-box linear model that was developed from a physiologically detailed multi-compartmental neurovascular unit model consisting of the vascular smooth muscle, perivascular space, synaptic space, and astrocyte glial cell. Then, model linearization was performed on the physiologically detailed nonlinear model to find appropriate complexity (Akaike information criterion) to fit functional near-infrared spectroscopy (fNIRS) based measure of blood volume changes, called cerebrovascular reactivity (CVR), to high-definition (HD) tDCS. The grey-box linear model was applied on the fNIRS-based CVR during the first 150 seconds of anodal HD-tDCS in eleven healthy humans. The grey-box linear models for each of the four nested pathways starting from tDCS scalp current density that perturbed synaptic potassium released from active neurons for Pathway 1, astrocytic transmembrane current for Pathway 2, perivascular potassium concentration for Pathway 3, and voltage-gated ion channel current on the smooth muscle cell for Pathway 4 were fitted to the total hemoglobin concentration (tHb) changes from optodes in the vicinity of 4x1 HD-tDCS electrodes as well as on the contralateral sensorimotor cortex. We found that the tDCS perturbation Pathway 3 presented the least mean square error (MSE, median <2.5%) and the lowest Akaike information criterion (AIC, median -1.726) from the individual grey-box linear model fitting at the targeted-region. Then, minimal realization transfer function with reduced-order approximations of the grey-box model pathways was fitted to the ensemble average tHb time series. Again, Pathway 3 with nine poles and two zeros (all free parameters), provided the best Goodness of Fit of 0.0078 for Chi-Square difference test of nested pathways. Therefore, our study provided a systems biology approach to investigate the initial transient hemodynamic response to tDCS based on fNIRS tHb data. Future studies need to investigate the steady-state responses, including steady-state oscillations found to be driven by calcium dynamics, where transcranial alternating current stimulation may provide frequency-dependent physiological entrainment for system identification. We postulate that such a mechanistic understanding from system identification of the hemodynamics response to transcranial electrical stimulation can facilitate adequate delivery of the current density to the neurovascular tissue under simultaneous portable imaging in various cerebrovascular diseases.
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The effects of transcranial direct current stimulation on upper-limb function post-stroke: A meta-analysis of multiple-session studies. Clin Neurophysiol 2021; 132:1897-1918. [PMID: 34157634 DOI: 10.1016/j.clinph.2021.05.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 04/21/2021] [Accepted: 05/10/2021] [Indexed: 02/06/2023]
Abstract
OBJECTIVE To systematically review how patient characteristics and/or transcranial direct current stimulation (tDCS) parameters influence tDCS effectiveness in respect to upper limb function post-stroke. METHODS Three electronic databases were searched for sham-controlled randomised trials using the Fugl-Meyer Assessment for upper extremity as outcome measure. A meta-analysis and nine subgroup-analyses were performed to identify which tDCS parameters yielded the greatest impact on upper limb function recovery in stroke patients. RESULTS Eighteen high-quality studies (507 patients) were included. tDCS applied in a chronic stage yields greater results than tDCS applied in a (sub)acute stage. Additionally, patients with low baseline upper limb impairments seem to benefit more from tDCS than those with high baseline impairments. Regarding tDCS configuration, all stimulation types led to a significant improvement, but only tDCS applied during therapy, and not before therapy, yielded significant results. A positive dose-response relationship was identified for current/charge density and stimulation duration, but not for number of sessions. CONCLUSION Our results demonstrate that tDCS improves upper limb function post-stroke. However, its effectiveness depends on numerous factors. Especially chronic stroke patients improved, which is promising as they are typically least amenable to recovery. SIGNIFICANCE The current work highlights the importance of several patient-related and protocol-related factors regarding tDCS effectiveness.
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