Effects of tDCS on Language Recovery in Post-Stroke Aphasia: A Pilot Study Investigating Clinical Parameters and White Matter Change with Diffusion Imaging

White Matter Hyperintensities as a Predictor of Aphasia Recovery

OBJECTIVE

To examine the relation between baseline white matter hyperintensities (WMH) and change in naming, content production, and efficiency after treatment in subacute aphasia. We hypothesized that more severe baseline WMH would result in less improvement with treatment.

DESIGN

Retrospective analysis of a cohort from a double-blind randomized controlled trial (RCT).

SETTING

Outpatient clinical setting or participant home.

PARTICIPANTS

We retrospectively reviewed imaging and behavioral data for 52 participants with subacute aphasia due to left-hemisphere ischemic stroke enrolled in the RCT. RCT inclusion criteria: English proficiency, normal/corrected-to-normal hearing/vision, and no history of neurologic conditions other than the stroke resulting aphasia. One participant with a chronic right-hemisphere lesion was retained as she presented with no residual deficits on neurologic examination. Individuals with scalp sensitivities or on medications that lower seizure threshold or any N-methyl-D-aspartate (NMDA) antagonists were excluded. Of the 52 participants, for this analysis, 2 were excluded for not having a magnetic resonance imaging, and 7 were excluded for not participating in treatment or pre/post assessment for at least 1 outcome, resulting in final sample of 43 participants (20 women sex, M [SD] age=64.4 [11.9] and M [SD] education=14.9 [3.1] years).

INTERVENTIONS

Participants received 15 sessions (2-3 times/week) of computerized lexical-semantic (ie, verification) treatment with [sham/active] transcranial direct current stimulation (tDCS). Sessions were approximately 45 minutes each (tDCS for first 20 minutes).

MAIN OUTCOME MEASURES

Naming accuracy, content units (CUs, a measure of semantically accurate production), and efficiency (ie, syllables/CU) on a picture description task.

RESULTS

Periventricular WMH severity was independently associated with recovery in picture naming for the active tDCS group. Deep WMH severity was associated with recovery for CU production for the sham tDCS group.

CONCLUSION

Baseline periventricular and deep WMH, among other factors, may be an important consideration for prognosis and treatment planning, especially when considered in conjunction with tDCS treatment.

The role of language-related functional brain regions and white matter tracts in network plasticity of post-stroke aphasia

The neural mechanisms underlying language recovery after a stroke remain controversial. This review aimed to summarize the plasticity and reorganization mechanisms of the language network through neuroimaging studies. Initially, we discussed the involvement of right language homologues, perilesional tissue, and domain-general networks. Subsequently, we summarized the white matter functional mapping and remodeling mechanisms associated with language subskills. Finally, we explored how non-invasive brain stimulation (NIBS) promoted language recovery by inducing neural network plasticity. It was observed that the recruitment of right hemisphere language area homologues played a pivotal role in the early stages of frontal post-stroke aphasia (PSA), particularly in patients with larger lesions. Perilesional plasticity correlated with improved speech performance and prognosis. The domain-general networks could respond to increased "effort" in a task-dependent manner from the top-down when the downstream language network was impaired. Fluency, repetition, comprehension, naming, and reading skills exhibited overlapping and unique dual-pathway functional mapping models. In the acute phase, the structural remodeling of white matter tracts became challenging, with recovery predominantly dependent on cortical activation. Similar to the pattern of cortical activation, during the subacute and chronic phases, improvements in language functions depended, respectively, on the remodeling of right white matter tracts and the restoration of left-lateralized language structural network patterns. Moreover, the midline superior frontal gyrus/dorsal anterior cingulate cortex emerged as a promising target for NIBS. These findings offered theoretical insights for the early personalized treatment of aphasia after stroke.

The effectiveness and safety of noninvasive brain stimulation technology combined with speech training on aphasia after stroke: A systematic review and meta-analysis

BACKGROUND

Although the effectiveness of noninvasive brain stimulation (NIBS) technology in assisting rehabilitation is widely recognized, its therapeutic efficacy in patients with poststroke aphasia (PSA) requires further validation. Here, we aimed to explore the efficacy and safety of the NIBS technique combined with speech training in PSA by traditional Meta-analysis and to compare the intervention effects of the 2 NIBS techniques by Network meta-analysis.

METHODS

Randomized controlled trials of the NIBS technique combined with speech training for treating PSA in 9 databases, including Web of Science, PubMed, and CNKI, and 2 clinical trial registries were searched by computer. Literature screening was performed using EndNote X9 software, and data analysis and presentation of results were performed using RevMan 5.4.1 and Stata 17.0 software.

RESULTS

Screening yielded 17 studies with 1013 patients with PSA. Meta-analysis showed that aphasia quotient scores were higher in the intervention group than in the control group [standardized mean difference (SMD) = 1.06, 95% confidence interval (CI) (0.63, 1.49), Z = 4.80, P < .00001]; Western aphasia battery scores on all 4 subscales were higher than those of the control group, the spontaneous language score is [SMD = 0.62, 95% CI (0.46, 0.78), Z = 7.52, P < .00001], the listening comprehension score is [SMD = 0.46, 95% CI (0.30, 0.62), Z = 5.62, P < .00001], the repetition score is [SMD = 1.14, 95% CI (0.59, 1.70), Z = 4.04, P < .0001], the naming score is [SMD = 1.06, 95% CI (0.79, 1.32), Z = 7.85, P < .00001]; The effective rate of the intervention group was higher than that of the control group [odd ratio = 4.19, 95% CI (2.39, 7.37), Z = 4.99, P < .00001]. The results of the Network meta-analysis showed that the best probability ranking of the 2 NIBS techniques combined with speech training in improving aphasia quotient scores was repetitive transcranial magnetic stimulation group (92.2%) > transcranial direct current stimulation group (55.7%). Regarding safety, it was not found that the NIBS technique combined with speech training to treat PSA increases the risk of adverse reactions.

CONCLUSION

The NIBS technique combined with speech training can effectively improve the recovery of language function in PSA patients with minimal adverse effects, and the clinic can give priority to r TMS combined with speech training in treating PSA.

Non-invasive brain stimulation in the treatment of post-stroke aphasia: a scoping review

PURPOSE

Aphasia is an acquired language impairment that commonly results from stroke. Non-invasive brain stimulation (NIBS) might accelerate aphasia recovery trajectories and has seen mounting popularity in recent aphasia rehabilitation research. The present review aimed to: (1) summarise all existing literature on NIBS as a post-stroke aphasia treatment; and (2) provide recommendations for future NIBS-aphasia research.

MATERIALS AND METHODS

Databases for published and grey literature were searched using scoping review methodology. 278 journal articles, conference abstracts/posters, and books, and 38 items of grey literature, were included for analysis.

RESULTS

Quantitative analysis revealed that ipsilesional anodal transcranial direct current stimulation and contralesional 1-Hz repetitive transcranial magnetic stimulation were the most widely used forms of NIBS, while qualitative analysis identified four key themes including: the roles of the hemispheres in aphasia recovery and their relationship with NIBS; heterogeneity of individuals but homogeneity of subpopulations; individualisation of stimulation parameters; and much remains under-explored in the NIBS-aphasia literature.

CONCLUSIONS

Taken together, these results highlighted systemic challenges across the field such as small sample sizes, inter-individual variability, lack of protocol optimisation/standardisation, and inadequate focus on aphasiology. Four key recommendations are outlined herein to guide future research and refine NIBS methods for post-stroke aphasia treatment.