Opportunities for Guided Multichannel Non-invasive Transcranial Current Stimulation in Poststroke Rehabilitation

Abstract

Stroke is a leading cause of serious long-term disability worldwide. Functional outcome depends on stroke location, severity, and early intervention. Conventional rehabilitation strategies have limited effectiveness, and new treatments still fail to keep pace, in part due to a lack of understanding of the different stages in brain recovery and the vast heterogeneity in the poststroke population. Innovative methodologies for restorative neurorehabilitation are required to reduce long-term disability and socioeconomic burden. Neuroplasticity is involved in poststroke functional disturbances and also during rehabilitation. Tackling poststroke neuroplasticity by non-invasive brain stimulation is regarded as promising, but efficacy might be limited because of rather uniform application across patients despite individual heterogeneity of lesions, symptoms, and other factors. Transcranial direct current stimulation (tDCS) induces and modulates neuroplasticity, and has been shown to be able to improve motor and cognitive functions. tDCS is suited to improve poststroke rehabilitation outcomes, but effect sizes are often moderate and suffer from variability. Indeed, the location, extent, and pattern of functional network connectivity disruption should be considered when determining the optimal location sites for tDCS therapies. Here, we present potential opportunities for neuroimaging-guided tDCS-based rehabilitation strategies after stroke that could be personalized. We introduce innovative multimodal intervention protocols based on multichannel tDCS montages, neuroimaging methods, and real-time closed-loop systems to guide therapy. This might help to overcome current treatment limitations in poststroke rehabilitation and increase our general understanding of adaptive neuroplasticity leading to neural reorganization after stroke.

Transcranial Direct Current Stimulation in Poststroke Aphasia Recovery

“…On a final note, in light of the diversity of languages in tDCS/aphasia protocols 63 , it is interesting to consider the findings of recent neuro-linguistic studies which contend that language processing is activated in differing brain regions among speakers of languages that are structurally or morphologically dissimilar (e.g., Mandarin or Hebrew, compared with English, for example) 86–88 . Future tDCS-aphasia studies may therefore wish to compare tDCS montage, polarity and outcomes across linguistically disparate languages, as well as in bilingual versus monolingual speakers.…”

“…Unlike TMS, tDCS uses a low-intensity current of 1–2 mA to modulate (excite or inhibit) neuronal activity 63 . It has been explored in stroke rehabilitation as a method for encouraging brain plasticity, with results often lasting beyond the initial period of stimulation 62 .…”

“…Reviews of tDCS/aphasia literature are numerous 35,43,63,70 (Figure 2), yet recent meta analyses provide conflicting evidence of the effectiveness of tDCS for aphasia. One recent meta-analysis found statistically significant improvements in people with aphasia using tDCS 71 , while another meta-analysis reported some promise using cathodal stimulation over the contralateral hemisphere, but found no statistical significance regarding the effects of tDCS for aphasia overall 56 .…”

3D-printed head models for navigated non-invasive brain stimulation

“…Recent years have seen considerable interest in the clinical use of noninvasive brain stimulation (NIBS), including transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (tES) (Hummel et al, 2005; Dayan et al, 2013; Fox et al, 2013; Dunlop et al, 2016; Otal et al, 2016). One promising avenue of research that advances towards minimizing interindividual differences in patients’ responses to NIBS integrates brain imaging data, particularly functional and structural brain connectivity, to provide personalized, guided stimulation in clinical contexts (Fox et al, 2013; Dunlop et al, 2016; Otal et al, 2016).…”

“…One promising avenue of research that advances towards minimizing interindividual differences in patients’ responses to NIBS integrates brain imaging data, particularly functional and structural brain connectivity, to provide personalized, guided stimulation in clinical contexts (Fox et al, 2013; Dunlop et al, 2016; Otal et al, 2016). However, integrating imaging datasets into neuronavigation systems while simultaneously searching for the optimal stimulation site(s) in the clinic is a time-consuming process which requires operator training and may not be well-tolerated by some neurological and neuropsychiatric patient populations.…”