Functional Remodeling Associated With Language Recovery After Repetitive Transcranial Magnetic Stimulation in Chronic Aphasic Stroke

Hon

et al. 2023

Euro J of Neurology

Aphasic stroke is known to be caused by primary language circuit damage in the left hemisphere, leading to language ability deficits.Patients with nonfluent aphasia suffer from difficulty in daily communication and have poor recovery. In addition to speech therapy, several repetitive transcranial magnetic stimulation (rTMS) researches have shown promising results of rTMS to improve language recovery in aphasic stroke [1-3]. Based on the paradoxical function facilitation extending from the theory of interhemispheric imbalance, inhibitory rTMS application on the contralesional homologous Broca's area was reported as an efficient modality to recover the language ability in patients who suffered from aphasic stroke [2, 4]. Inhibitory rTMS can suppress the local over-activation of the

Section: Discussionsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Right arcuate fasciculus as outcome predictor after low‐frequency repetitive transcranial magnetic stimulation in nonfluent aphasic stroke

Hon

et al. 2023

Euro J of Neurology

“…The first four volumes of BOLD images were discarded from the subsequent analyses. Nuisance signals, including the six head movement parameters, the mean signal of cerebrospinal fluid, white matter, and global signal, were regressed out from the smoothed images, and low-frequency signals (0.01–0.1 Hz) were extracted using MATLAB software (2018b; Mathworks, Natick, MA) and an in-house scripts [ 47 ].…”

Section: Methodsmentioning

confidence: 99%

“…We performed a stepwise multivariate regression analysis to investigate the relationship between the altered functional sensorimotor network and the primary outcome of FMA-UE improvement (T2–T1 and T3–T1 as the dependent variables) in the real tDCS group and the sham group, respectively, as previously described [ 47 ]. To avoid an overfitting model, only the altered FC (z scores with large Cohen’s f 2 > 0.5) estimated by simple linear regression for FMA-UE improvements were included in the multivariate regression model with adjustment for age and sex [ 49 ].…”

Section: Methodsmentioning

confidence: 99%

Effects of bihemispheric transcranial direct current stimulation on motor recovery in subacute stroke patients: a double-blind, randomized sham-controlled trial

Hsu

J NeuroEngineering Rehabil

et al. 2023

Self Cite

Background Bihemispheric transcranial direct current stimulation (tDCS) of the primary motor cortex (M1) can simultaneously modulate bilateral corticospinal excitability and interhemispheric interaction. However, how tDCS affects subacute stroke recovery remains unclear. We investigated the effects of bihemispheric tDCS on motor recovery in subacute stroke patients. Methods We enrolled subacute inpatients who had first-ever ischemic stroke at subcortical regions and moderate-to-severe baseline Fugl-Meyer Assessment of Upper Extremity (FMA-UE) score 2–56. Participants between 14 and 28 days after stroke were double-blind, randomly assigned (1:1) to receive real (n = 13) or sham (n = 14) bihemispheric tDCS (with ipsilesional M1 anode and contralesional M1 cathode, 20 min, 2 mA) during task practice twice daily for 20 sessions in two weeks. Residual integrity of the ipsilesional corticospinal tract was stratified between groups. The primary efficacy outcome was the change in FMA-UE score from baseline (responder as an increase ≥ 10). The secondary measures included changes in the Action Research Arm Test (ARAT), FMA-Lower Extremity (FMA-LE) and explorative resting-state MRI functional connectivity (FC) of target regions after intervention and three months post-stroke. Results Twenty-seven participants completed the study without significant adverse effects. Nineteen patients (70%) had no recordable baseline motor-evoked potentials (MEP-negative) from the paretic forearm. Compared with the sham group, the real tDCS group showed enhanced improvement of FMA-UE after intervention (p < 0.01, effect size η2 = 0.211; responder rate: 77% vs. 36%, p = 0.031), which sustained three months post-stroke (p < 0.01), but not ARAT. Interestingly, in the MEP-negative subgroup analysis, the FMA-UE improvement remained but delayed. Additionally, the FMA-LE improvement after real tDCS was not significantly greater until three months post-stroke (p < 0.01). We found that the individual FMA-UE improvements after real tDCS were associated with bilateral intrahemispheric, rather than interhemispheric, FC strengths in the targeted cortices, while the improvements after sham tDCS were associated with predominantly ipsilesional FC changes after adjustment for age and sex (p < 0.01). Conclusions Bihemispheric tDCS during task-oriented training may facilitate motor recovery in subacute stroke patients, even with compromised corticospinal tract integrity. Further studies are warranted for tDCS efficacy and network-specific neuromodulation. Trial registration: This study is registered with ClinicalTrials.gov: (ID: NCT02731508).

“…The elucidation of the mechanisms of aphasia recovery in stroke is clinically important and essential for establishing effective neuro-rehabilitation strategies. More specifically, novel non-invasive brain stimulation therapies such as repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS) can be applied to specific neural structures which contribute to aphasia recovery [ 7 , 8 , 9 , 10 ].…”

Section: Introductionmentioning

confidence: 99%

Diffusion Tensor Tractography Studies on Recovery Mechanisms of Aphasia in Stroke Patients: A Narrative Mini-Review

2022

Aphasia is a common and serious clinical feature of stroke. Various neural tracts are known to be involved in language processing. Diffusion tensor tractography (DTT) appears to be an appropriate imaging technique for the elucidation of the recovery mechanisms of aphasia in the language-related neural tracts in stroke patients. In this article, twelve previous DTT-based studies on the recovery mechanisms of aphasia in stroke were reviewed. We classified the twelve studies into the following three categories according to the recovery mechanisms: recovery via the neural tracts in the dominant hemisphere (eight studies), via transcallosal fibers (two studies), and via the neural tracts in the non-dominant hemisphere (two studies). Although there are various neural tracts for language processing, eight of the ten studies focused only on the role of the arcuate fasciculus (AF) in the recovery process. Consequently, it appears from the studies that only one recovery mechanism of aphasia via the restoration of the integrity of the injured AF in the dominant hemisphere was clearly demonstrated. However, because various neural tracts are involved in language processing, there could be other mechanisms that have not yet been elucidated. Therefore, further original studies involving a larger number of patients with aphasia in stroke should be encouraged forthwith. Further studies involving various lesion locations and severity levels of injuries to the language-related neural tracts are also necessary because the recovery mechanisms of aphasia in stroke could be dependent on these factors.