Cerebellar transcranial direct current stimulation improves quality of life in individuals with chronic post-stroke aphasia

doi:10.21203/rs.3.rs-4708028/v1

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Cerebellar transcranial direct current stimulation improves quality of life in individuals with chronic post-stroke aphasia

https://doi.org/10.21203/rs.3.rs-4708028/v1

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Background

The cerebellum has emerged as a potential target for transcranial direct current stimulation (tDCS) in post-stroke aphasia (PSA) due to its role in language processing and relative preservation compared to supratentorial lesions. Recent evidence also highlights the cerebellum's involvement in affective and social processes, suggesting potential broader effects of cerebellar modulation. This study investigated the efficacy of anodal tDCS over the right cerebellum paired with speech and language therapy in enhancing language functions and quality of life in individuals with PSA.

Methods

Twenty-two participants with chronic PSA received cerebellar tDCS, while historical sham control data from 25 participants were obtained. Language outcomes were assessed using the Western Aphasia Battery-Revised (WAB-R), and secondary outcomes included patient-reported measures of communication effectiveness and quality of life. Mixed-design analyses of variance were conducted to examine treatment effects.

Results

No significant Group x Time interaction was found for WAB-R scores, indicating that tDCS did not provide additional language benefits over speech therapy. However, a significant Group x Time interaction was observed for the Stroke and Aphasia Quality of Life Scale-39 scores, driven by improvements in the Psychosocial, Physical, and Energy subdomains in the tDCS group.

Conclusions

Cerebellar tDCS did not significantly improve language outcomes in PSA individuals but enhanced specific aspects of quality of life. These findings highlight the cerebellum's multifaceted role in cognitive, affective, and sensorimotor processes. Future research should focus on conducting well-powered, randomized, double-blind, and concurrent trials to validate these findings and explore optimal stimulation parameters in PSA rehabilitation.

Clinical Trial Registration: The trial is registered at ClinicalTrials.gov with the registration number NCT03699930. The date of registration is 10/05/2018.

Biological sciences/Psychology

Health sciences/Medical research

Health sciences/Neurology

Aphasia

Stroke

Transcranial direct current stimulation (tDCS)

Cerebellum

Stroke and Aphasia Quality of Life Scale-39 (SAQOL-39)

Psychosocial

Aphasia, a language disorder characterized by deficits in the expression and/or comprehension of spoken and written language, is a common consequence of stroke (Berthier 2005). Despite the availability of traditional speech and language therapy (SLT), many individuals with post-stroke aphasia (PSA) struggle to achieve satisfactory language outcomes. In recent years, transcranial direct current stimulation (tDCS) has emerged as a promising adjuvant treatment to enhance language recovery in PSA (Biou et al. 2019). TDCS aims to modulate the excitability of brain regions, where anodal stimulation increases cortical excitability and cathodal stimulation decreases it (Nitsche and Paulus 2000), thereby facilitating neuroplasticity and recovery.

The majority of tDCS studies in PSA have focused on stimulating intact left perilesional regions, such as Broca's area (Polanowska et al. 2013; Marangolo et al. 2013; Campana et al. 2015), Wernicke's area (Fiori et al. 2011; Marangolo et al. 2014), the motor cortex (Meinzer et al. 2016; Branscheidt et al. 2018), or the dorsolateral prefrontal cortex (Pestalozzi et al. 2018). However, the efficacy of cortical stimulation may be limited by several factors. First, the presence of stroke lesions can lead to variable responses to direct stimulation over the damaged area, depending on the extent of the damage (Turkeltaub et al. 2016). Second, the heterogeneity of supratentorial stroke lesions can make it challenging to determine the optimal stimulation site. While some studies have used functional MRI to guide tDCS targeting (Fridriksson et al. 2011, 2018), such approach is costly and not readily feasible in a clinical environment.

As an alternative target, the right cerebellum has been proposed for stimulation in post-stroke aphasia, as it is relatively intact compared to the supratentorial regions primarily affected in PSA. The right cerebellum has been associated with a host of cognitive and language functions (Stoodley and Schmahmann 2009; De Smet et al. 2013; Keren-Happuch et al. 2014), and both functional and structural connectivity studies have identified connections between the right cerebellum and contralateral fronto-temporo-parietal language association areas (Kelly and Strick 2003; Strick et al. 2009; Binder et al. 2009; Price 2012).

Promising results have been observed in both healthy volunteers and individuals with PSA following cerebellar tDCS. In healthy participants, cerebellar tDCS has led to improvements in verbal fluency (Turkeltaub et al. 2016) and verb generation (Pope and Miall 2012). Similarly, in post-stroke aphasia, cerebellar tDCS has been shown to enhance spelling (Sebastian et al. 2017), naming (Sebastian et al. 2020; Coemans et al. 2023), and verb generation (Marangolo et al. 2017). Furthermore, increased right cerebellar activation has been linked to better recovery in patients with aphasia (Szaflarski et al. 2013), suggesting that the right cerebellum may play a crucial role in language recovery post-stroke. The mechanisms underlying the effects of cerebellar tDCS on language processing are thought to involve the modulation of Purkinje cells (Pope and Miall 2012; van Dun et al. 2016), which are the primary output neurons of the cerebellar cortex and regulate the activity of deep cerebellar nuclei. By altering the excitability of Purkinje cells, cerebellar tDCS may induce changes in the firing patterns of the deep cerebellar nuclei, which in turn can influence the activity of distant cortical areas through cerebello-cortical projections (Grimaldi et al. 2016; van Dun et al. 2016). This is supported by our prior work, which uncovered neuroplasticity in the superior cerebellar peduncle, a major white matter tract carrying efferent fibers from the deep cerebellar nuclei, associated with improvement in spontaneous speech following anodal Broca’s tDCS in patients with PSA (Zheng et al. 2023). These findings suggest that modulating cerebellar activity, either directly through cerebellar tDCS or indirectly through cortical stimulation, may promote language recovery by inducing neuroplastic changes in the cerebello-cortical network.

Beyond its established roles in motor control and language processing, emerging evidence highlights the cerebellum’s involvement in affective and social cognition (Schmahmann 1996; Strick et al. 2009). Neuroimaging studies have revealed cerebellar activation during tasks involving emotion processing, empathy, mentalizing or theory of mind, and social interaction (Moriguchi et al. 2007; Van Overwalle et al. 2014, 2020; Beuriat et al. 2022; Petrosini et al. 2024). Lesion studies have shown that cerebellar damage can lead to cerebellar cognitive affective syndrome, characterized by impairments in affective regulation, executive function, linguistic processing, and visuospatial cognition (Schmahmann 2004; Hoche et al. 2016). Moreover, the cerebellum has been found to play a role in the regulation of mood and anxiety, with structural and functional cerebellar abnormalities observed in various psychiatric disorders (Shakiba 2014; Phillips et al. 2015). The cerebellum's dense connections with limbic and paralimbic regions, including the amygdala, hypothalamus, hippocampus, cingulate cortex, and medial prefrontal cortex, provide an anatomical basis for its involvement in emotional, social, and higher-order cognitive processing (Strick et al. 2009; Adamaszek et al. 2016). These diverse cerebellar functions suggest a potential for wide-ranging effects of cerebellar modulation beyond motor and language domains. However, the impact of cerebellar tDCS on this broad spectrum of functions in individuals with post-stroke aphasia remains largely unexplored.

Targeting the more preserved cerebellum may offer a more consistent and practical approach to addressing heterogeneous stroke lesions. While previous studies have investigated the effects of cerebellar tDCS on language production, its potential to enhance a broader range of language abilities (e.g., language comprehension) and its associated functions remains to be elucidated. The primary objective of this study was to evaluate the efficacy of anodal tDCS over the right cerebellum in enhancing both expressive and receptive language functions, as assessed by the Western Aphasia Battery-Revised (WAB-R) in individuals with chronic PSA. Additionally, given the cerebellum’s involvement in various cognitive and affective processes, we aimed to explore the effects of cerebellar tDCS on patient-reported secondary outcomes, particularly quality of life and communication effectiveness. To provide a robust evaluation of the intervention effects, the results were compared to a previous sham control dataset.

Participants

This study included 47 participants with chronic post-stroke aphasia, primarily resulting from left hemisphere strokes, with some participants exhibiting bilateral lesions. Lesion information for each participant is shown in Supplementary Table S1. MRI scans were not available from some patients; thus, lesion details were only available for 21/22 tDCS patients and 19/25 sham patients. The participants were divided into two groups: the cerebellar tDCS condition (n = 22) and sham condition (n = 25). We initially recruited 25 patients for cerebellar tDCS, but three dropped out due to either COVID-19 infection, schedule conflict, or lack of English proficiency. The cerebellar tDCS dataset were acquired between 2020-2022 with a non-randomized, double-blind design. The sham tDCS data were obtained from a previous study conducted between 2018-2020, which employed a randomized, double-blind design. Table 1 summarizes the participants’ demographic and clinical information. The inclusion criteria for participants were as follows: (1) a clinical diagnosis of aphasia resulting from ischemic or hemorrhagic stroke, (2) at least 12 months post-stroke, (3) aged 18 years or older, and (4) English proficiency. Participants with multiple strokes were also included. Exclusion criteria consisted of aphasia resulting from any neurological conditions other than stroke. All participants provided written informed consent prior to participating in the study. The study was approved by the Institutional Review Board of Casa Colina Hospital. The trial was registered on ClinicalTrials.gov as NCT03699930.

Study design

Following a double-blind design, both participants and experimenters who conducted the interventions and assessments were blinded to the allocation of participants. To incorporate the pre-existing control data while preserving the study’s blinded nature, participants in the active tDCS group were told they could receive either real cerebellar tDCS or sham tDCS, paired with speech and language therapy. However, all participants received real tDCS. The P.I. was the only person aware of the allocation. Allocation concealment was accomplished by assigning a 6-digit code per participant.

For both the sham and cerebellar tDCS groups, the primary outcome measure was collected at two time-points, within one week before the intervention (pre-intervention) and one week after the intervention (post-intervention). Secondary outcome measures were collected at three time points: pre-intervention, post-intervention, and during a 3-month follow-up.

Outcome measures

The primary outcome measure was change in language scores as assessed by the Western Aphasia Battery-Revised (WAB-R). This evaluation encompassed four distinct subscales, namely spontaneous speech (SS), auditory verbal comprehension (AVC), name and word finding (NWF), and repetition (REP). The scores from these four subscales were consolidated to compute the aphasia quotient (AQ [range 0-100]), providing a measure of aphasia severity, with lower scores reflecting worse language performance. Secondary outcome measures (SOMs) were patient and/or caregiver self-reported and comprised the Communication Outcomes after Stroke (COAST), Carer COAST, Stroke and Aphasia Quality of Life Scale-39 (SAQOL-39), and Patient-Reported Outcomes Measurement Information System (PROMIS-Global). Higher scores indicate better outcomes. The COAST and Carer-COAST surveys consist of 20 items evaluating post-stroke communication effectiveness. The PROMIS-Global (10 items) and SAQOL-39 (39 items) evaluate patients' quality of life and overall well-being. The SAQOL-39 assesses functioning in four domains: physical, psychosocial, communication, and energy.

Transcranial direct current stimulation

TDCS stimulation was paired with speech and language therapy and was delivered for 20 minutes using a constant current stimulator (Soterix Medical 1 x 1 clinical trials device). Consistent with other studies on cerebellar tDCS (Sebastian 2021; DeMarco et al., 2022), the current study utilized 2 mA tDCS generated between two 5cm x 5cm saline-soaked sponges. The anode (active electrode) was placed on the right cerebellar cortex, 1cm under, and 4cm lateral to the inion (approximately over the cerebellar lobule VII) (Pope and miall, 2012). The reference electrode (cathode) was placed on the right deltoid. The current was ramped up to 2 mA over 30 seconds, maintained for 20 minutes, then ramped down over 30 seconds.

In the sham condition (data previously collected), after the initial ramp-up period of 30 seconds, the intensity was promptly reduced to 0 mA in the subsequent 30-second ramp-down phase and maintained at this level throughout the session. Each stimulation condition, whether real or sham, was coupled with a 20-minute speech and language therapy session. Participants underwent this procedure for five consecutive days.

Speech and language therapy

Participants underwent approximately 20 minutes of personalized speech and language therapy, tailored by the therapist’s clinical judgment, and guided by standardized assessments. The primary goal of the therapy was to enhance expressive language skills, employing a range of evidence-based treatment techniques, such as Melodic Intonation Therapy, Language Stimulation Approach, Modified Response Elaboration Training, Semantic Feature Analysis Treatment, Verb Network Strengthening Treatment, Sound Production Treatment, Integral Stimulation, and Word Retrieval Cuing Strategies (e.g., phonological and semantic cuing). For participants with severe auditory comprehension deficits that impeded their ability to understand tasks, the therapy incorporated targeted auditory comprehension interventions. The therapy sessions prioritized areas that would yield the most significant improvements in the participant's functional communication skills.

Statistical Analysis

To identify potential confounding variables, we compared the demographic and clinical characteristics of the two groups, including age, gender, time since injury (TSI), stroke type (ischemic or hemorrhagic), fluency (fluent or non-fluent), baseline AQ, handedness, and lesion hemisphere. Independent samples t-tests were used for continuous variables, while chi-square tests were employed for categorical variables. TSI was found to be significantly different between the two groups and was therefore included as a covariate in subsequent analyses.

Mixed-design analyses of variance (ANOVAs) were conducted to examine the treatment effects, with Group (tDCS or sham) as the between-subjects factor and Time (pre-intervention or post-intervention) as the within-subjects factor. The primary outcome measure consisted of scores from WAB-R, including AQ, SS, AVC, NWF, and REP. Secondary outcomes included scores from COAST, Carer COAST, PROMIS-Global, and SAQOL-39.

After finding a significant Time X Group interaction for SAQOL-39 scores, we conducted a follow-up analysis (Mixed ANOVAs with TSI as a covariate) to determine which subdomains (Physical, Psychosocial, Communication, Energy) of SAQOL-39 were driving the significance. Due to the limited number of questions (four) in the Energy subdomain, which may have resulted in a restricted range of scores and reduced variability, we combined the Energy and Physical subdomain scores. Three participants were missing SAQOL-39 data, resulting in n = 20 for tDCS and n = 24 for sham.

Due to challenges faced during the COVID-19 pandemic, many participants were unable to complete the 3-month follow-up assessment, resulting in insufficient data for group analysis at this time point. Consequently, only pre-intervention and post-intervention scores were included in the statistical analyses.

The two groups did not differ significantly in age, gender, stroke type, fluency, or AQ at baseline, but did differ in time since injury (Table 1); the tDCS group had significantly shorter TSI compared to the sham group. Therefore, TSI served as a covariate in the ANOVA analyses. The ANOVA results revealed no Group x Time interaction for the WAB-R scores, indicating that the change in language performance over time did not differ between the tDCS and sham groups. We, did, however, find a significant Group x Time interaction (F(1,41) = 5.36, P = 0.026, \(\:{\eta\:}^{2}\) = 0.005) for SAQOL-39 (total scores) (Fig. 1). The tDCS group showed a significant increase in SAQOL-39 scores from pre- to post-intervention (mean change = 8.7, SD = 10), while the sham group did not (mean change = 1.1, SD = 12). Further analysis of the SAQOL-39 subdomains revealed significant Time X Group interactions for both Psychosocial (F(1,41) = 6.61, P = 0.014, \(\:{\eta\:}^{2}\) = 0.012) and Physical + Energy subdomains (F(1,41) = 5.79, P = 0.021, \(\:{\eta\:}^{2}\) = 0.003); see Fig. 1. The tDCS group demonstrated significant increases in Psychosocial (mean change = 4.1, SD = 5) and Physical + Energy (mean change = 3.2, SD = 4.4) from pre- to post-intervention, whereas the sham group showed no significant changes (Psychosocial: mean change = 0.54, SD = 4.3; Physical + Energy: mean change = 0.29, SD = 6.9). No significant differences were found between the groups for the Communication subdomain. No other secondary outcomes showed significant differences between groups after treatment. No severe adverse events were reported in either group.

This study aimed to investigate the effectiveness of anodal tDCS over the right cerebellum in enhancing language functions in individuals with post-stroke aphasia. Despite the growing interest in the cerebellum as a potential target for neuromodulation in aphasia treatment, our results did not demonstrate significant improvements in language processing, as measured by the WAB-R, in the cerebellar tDCS group compared to the sham group. The lack of significant interaction effects between Group and Time on the primary outcome measure (WAB-R scores) suggests that cerebellar tDCS did not provide additional benefits over traditional speech and language therapy alone. This finding is inconsistent with our initial hypothesis and some previous studies that have reported positive effects of cerebellar tDCS on language functions (Sebastian et al. 2017, 2020; DeMarco et al. 2021). However, it is important to note that the current literature on cerebellar tDCS in aphasia treatment is still limited, and the optimal stimulation parameters and treatment protocols remain unclear.

Despite the lack of significant effects on the WAB-R scores, we found a significant Group x Time interaction for the SAQOL-39 total scores, driven by improvements in Psychosocial and Physical + Energy subdomains. The cerebellar tDCS group showed a significant increase in SAQOL-39 scores from pre- to post-intervention, while the sham group did not. These findings suggest that cerebellar tDCS may have potential benefits for enhancing specific aspects of quality of life in individuals with PSA, even in the absence of measurable changes in language performance.

The improvement in the Psychosocial subdomain may be attributed to the role of the cerebellum in social cognition and emotional processing (Van Overwalle et al. 2020; Clausi et al. 2022b). The posterior cerebellum, particularly the lateral region targeted by our tDCS intervention, has been implicated in complex cognitive-social processes such as mentalizing, emotion attribution, and social judgment (Leggio and Olivito 2018; Van Overwalle et al. 2019, 2020). A meta-analysis by Van Overwalle et al. (2014) found consistent activation in the posterolateral cerebellum during various social and cognitive tasks (Van Overwalle et al. 2014). Moreover, anodal cerebellar tDCS applied to the posterior cerebellum has been shown to improve the ability to recognize and attribute mental states to others (Clausi et al. 2022a). These findings are further supported by preclinical studies, where stimulating the right posterolateral cerebellum in an autism mouse model led to improvements in social behaviors (Stoodley et al. 2017).

In addition to its role in social cognition, the cerebellum has reciprocal monosynaptic connections with the hypothalamic-pituitary-adrenal (HPA) axis (Schutter 2012; Benagiano et al. 2018), a key component of the neuroendocrine system that regulates the body’s response to stress. Dysregulation of the HPA axis has been linked to various psychiatric disorders, which are often associated with impaired psychosocial functioning (Zorn et al. 2017). Neuroimaging studies have found structural and functional abnormalities in the cerebellum of patients with various psychiatric and stress-related disorders (Konarski et al. 2005; Phillips et al. 2015; Romer et al. 2018; Depping et al. 2018). Given the cerebellum’s involvement in both social cognition and stress regulation, cerebellar tDCS may have modulated the neural networks involved in processing social cues and regulating emotional responses, leading to better psychosocial functioning and well-being in individuals with PSA.

Following the discussion on the cerebellum’s role in social cognition and emotional regulation, it is important to note that the posterior cerebellum is also critically involved in sensorimotor functioning (Manto et al. 2012), albeit to a lesser extent than the anterior cerebellum. While the anterior cerebellum is primarily associated with basic motor control, the posterior cerebellum may contribute to more complex aspects of motor control and planning that integrate cognitive and affective processes (Kelly and Strick 2003; Strick et al. 2009). Functional neuroimaging studies have shown activation of the posterior cerebellum during various sensorimotor tasks (Grodd et al. 2001; Takanashi et al. 2003; Diedrichsen et al. 2005; Cheng et al. 2008; Schlerf et al. 2010). Moreover, stimulating the posterior cerebellum may also have indirectly influenced the anterior cerebellum through the extensive network of cerebellar connections (Kelly and Strick 2003). Cerebellar tDCS may have enhanced the efficiency of neural networks responsible for sensorimotor control, resulting in increased physical functioning and energy levels, aligning with cerebellum’s well-established role in motor functioning.

Interestingly, the Communication subdomain did not show significant differences between the tDCS and sham groups, which is consistent with the lack of significant effects on the primary language outcome measures (WAB-R scores). This suggests that while cerebellar tDCS may have the potential to improve certain aspects of quality of life, its direct impact on language functions remains unclear. The differential effects of cerebellar tDCS on the SAQOL-39 subdomains highlight the need for future research to investigate the specific mechanisms through which cerebellar stimulation may influence different aspects of functioning and well-being in individuals with aphasia. Moreover, the development of targeted intervention protocols that combine cerebellar tDCS with focused rehabilitation strategies for psychosocial and physical functioning may help to optimize the potential benefits of this neuromodulation technique.

In a previous clinical trial, we investigated the efficacy of tDCS applied over Broca's area compared to sham stimulation in individuals with post-stroke aphasia (Zheng et al. 2023). While the study collected SAQOL-39 scores, no significant differences were found between the Broca's tDCS and sham groups in terms of quality of life outcomes. In contrast, the current study demonstrated significant improvements in SAQOL-39 scores, particularly in the Psychosocial and Physical + Energy subdomains, following cerebellar tDCS compared to sham stimulation. These findings suggest that targeting the cerebellum with tDCS may have unique potential in enhancing quality of life outcomes in PSA, possibly due to its role in modulating cognitive, affective, and sensorimotor processes that extend beyond language-specific functions. The lack of significant effects on SAQOL-39 scores when targeting Broca's area highlights the specific contribution of the cerebellum to these quality of life improvements.

The significant improvement in SAQOL-39 scores for the cerebellar tDCS group, in the absence of significant changes in other secondary outcome measures, may be attributed to the comprehensive nature of the SAQOL-39. This 39-item scale assessed multiple domains, which may have enabled it to capture subtle changes in participants' overall well-being and functioning. In contrast, the COAST (20 items) and PROMIS-Global (10 items) are shorter scales focusing on specific aspects of communication or quality of life. The broader scope and higher number of items in the SAQOL-39 may have increased its sensitivity to detect minor improvements in quality of life that were not captured by the other secondary outcome measures.

However, it is important to acknowledge the limitations of this study. One major limitation of the study is the difference in data collection periods between the two groups. The cerebellar tDCS data were collected during the COVID-19 pandemic, which could have introduced additional confounding factors. For instance, participants in the cerebellar tDCS group wore clear masks during treatment sessions to comply with pandemic safety protocols, while participants in the sham group, whose data were acquired before the pandemic, did not. The use of clear masks might have affected the quality of communication and the effectiveness of speech and language therapy, resulting in null results for the primary outcome. Additionally, psychosocial factors related to the pandemic, such as changes in participants’ mental health, social support, and access to healthcare services could have influenced the participants' performance and response to treatment. Furthermore, the non-randomized design for the cerebellar tDCS group may have introduced selection bias and reduced the comparability between the two groups.

Another limitation of the study is the relatively short duration of the therapy sessions. The 20-minute sessions might not have been sufficient to induce measurable changes in language performance, especially considering the chronic nature of the participants' aphasia. Future studies should explore the effects of longer therapy sessions or more intensive treatment protocols. Moreover, the sensitivity of the WAB-R in detecting small gains in language functions might have been limited. While the WAB-R is a widely used and validated assessment tool for aphasia, it may not capture subtle improvements in specific language domains. Future research could benefit from the inclusion of more sensitive and targeted outcome measures to evaluate the effects of cerebellar tDCS on different aspects of language processing.

In conclusion, our study did not provide evidence for the efficacy of cerebellar tDCS in improving language functions in individuals with chronic post-stroke aphasia. However, the significant improvement in SAQOL-39 scores, particularly in the Psychosocial and Physical + Energy subdomains, suggests potential benefits of cerebellar tDCS group on participants’ quality of life. These findings highlight the cerebellum’s multifaceted role in modulating cognitive, affective, and sensorimotor processes. While these results are promising, they should be interpreted with caution due to the study’s limitations, including the non-randomized design and the potential confounding effects of COVID-19 pandemic. Future research should focus on conducting larger-scale, parallel, randomized controlled trials with longer follow-up periods to establish the clinical utility of cerebellar tDCS in aphasia treatment. Additionally, employing more sensitive and targeted outcome measures, as well as exploring optimal stimulation parameters and treatment protocols, may help to better understand the potential of cerebellar tDCS in enhancing language recovery and quality of life in individuals with post-stroke aphasia.

Ethics Approval and Consent to Participate:

This study was conducted in accordance with the Declaration of Helsinki. Ethical approval was granted by the Institutional Review Board of Casa Colina Hospital. All participants provided written informed consent prior to participating in the study

Funding:

This work was supported by Ability Central.

Author Contribution

Z.S.Z.: Conceptualization, Methodology, Analysis, Writing-Original Draft, Visualization, Supervision, Funding Acquisition.J.W.: Data Curation, Investigation, Project Administration.S.L.: Investigation, Clinical Assessment.K.W.: Analysis.B.Z.: Visualization.M.H.: Clinical Assessment.E. R.: Project Administration, Resources.C. S.: Resources, Validation.All authors reviewed the manuscript.

Data Availability

Due to privacy and ethical considerations, data are only available upon request by contacting the corresponding author, Z.S.Z., at [email protected].

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Table 1. Patient Demographic and Clinical Details

Data are shown as Mean ± SD unless otherwise specified. NA = MRI not available

No competing interests reported.

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Cerebellar transcranial direct current stimulation improves quality of life in individuals with chronic post-stroke aphasia

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