Low frequency transcranial magnetic stimulation in subacute ischemic stroke: Number of sessions that altered cortical excitability

Neuropsychological and Anatomical-Functional Effects of Transcranial Magnetic Stimulation in Post-Stroke Patients with Cognitive Impairment and Aphasia: A Systematic Review

Transcranial magnetic stimulation (TMS) has been found to be promising in the neurorehabilitation of post-stroke patients. Aphasia and cognitive impairment (CI) are prevalent post-stroke; however, there is still a lack of consensus about the characteristics of interventions based on TMS and its neuropsychological and anatomical-functional benefits. Therefore, studies that contribute to creating TMS protocols for these neurological conditions are necessary. To analyze the evidence of the neuropsychological and anatomical-functional TMS effects in post-stroke patients with CI and aphasia and determine the characteristics of the most used TMS in research practice. The present study followed the PRISMA guidelines and included articles from PubMed, Scopus, Web of Science, ScienceDirect, and EMBASE databases, published between January 2010 and March 2023. In the 15 articles reviewed, it was found that attention, memory, executive function, language comprehension, naming, and verbal fluency (semantic and phonological) are the neuropsychological domains that improved post-TMS. Moreover, TMS in aphasia and post-stroke CI contribute to greater frontal activation (in the inferior frontal gyrus, pars triangularis, and opercularis). Temporoparietal effects were also found. The observed effects occur when TMS is implemented in repetitive modality, at a frequency of 1 Hz, in sessions of 30 min, and that last more than 2 weeks in duration. The use of TMS contributes to the neurorehabilitation process in post-stroke patients with CI and aphasia. However, it is still necessary to standardize future intervention protocols based on accurate TMS characteristics.

The role of dorsolateral striatum in the effects of deep cerebellar stimulation-mediated motor recovery following ischemic stroke in rodents

Despite great advances in acute care and rehabilitation, stroke remains the leading cause of motor impairment in the industrialized world. We have developed a deep brain stimulation (DBS)-based approach for post-stroke rehabilitation that has shown reproducible effects in rodent models and has been recently translated to humans. Mechanisms underlying the rehabilitative effects of this novel therapy have been largely focused on the ipsilesional cortex, including cortical reorganization, synaptogenesis, neurogenesis and greater expression of markers of long-term potentiation. The role of subcortical structures on its therapeutic benefits, particularly the striatum, remain unclear. In this study, we compared the motor rehabilitative effects of deep cerebellar stimulation in two rodent models of cerebral ischemia: a) cortical ischemia; and b) combined striatal and cortical ischemia. All animals underwent the same procedures, including implantation of the electrodes and tethered connections for stimulation. Both experimental groups received four weeks of continuous lateral cerebellar nucleus (LCN) DBS and each was paired with a no stimulation, sham, group. Fine motor function was indexed using the pasta matrix task. Brain tissue was harvested for histology and immunohistochemical analyses. In the cortical-only ischemia, the average pasta matrix performance of both sham and stimulated groups reduced from 19 to 24 pieces to 7-8 pieces following the stroke induction. At the end of the four-week treatment, the performance of stimulated group was significantly greater than that of sham group (14 pieces vs 7 pieces, p < 0.0001). Similarly, in the combined cortical and striatal ischemia, the performance of both sham and stimulated groups reduced from 29 to 30 pieces to 7-11 pieces following the stroke induction. However, at the end of the four-week treatment, the performance of stimulated group was not significantly greater than that of sham group (15 pieces vs 11 pieces, p = 0.452). In the post-mortem analysis, the number of cells expressing CaMKIIα at the perilesional cortical and striatum of the LCN DBS treated animals receiving cortical-only stroke elevated but not those receiving cortical+striatal stroke. The current findings suggested that the observed, LCN DBS-enhanced motor recovery and perilesional plasticity may involve striatal mechanisms.

Barriers to Enrollment in Post-Stroke Brain Stimulation in a Racially and Ethnically Diverse Population

BACKGROUND AND PURPOSE

Brain stimulation is an adjuvant strategy to promote rehabilitation after stroke. Here, we evaluated the influence of inclusion/exclusion criteria on enrollment in a transcranial direct current stimulation (tDCS) trial in the context of a racially/ethnically diverse acute stroke service at University of Texas Southwestern (UTSW).

METHODS

3124 (59.7 ± 14.5 years) racially/ethnically diverse (38.4% non-Hispanic white, (W), Hispanic (H) 22%, African American (AA) 33.5%, Asian (A) 2.3%) patients were screened in the acute stroke service at UTSW. Demographics, stroke characteristics, and reasons for exclusion were recorded prospectively.

RESULTS

2327 (74.5%) patients had a verified stroke. Only 44 of them (1.9%) were eligible. Causes for exclusion included in order of importance: (1) magnitude of upper extremity (UE) motor impairment, (2) prior strokes (s), (3) hemorrhagic stroke, (4) psychiatric condition or inability to follow instructions, and (5) old age, of these (2) and (4) were more common in AA patients but not in other minorities. 31 of the 44 eligible individuals were enrolled (W 1.68%, H 1.37%, AA .77%, A 3.774%). 90.5% of verified stroke patients did not exhibit contraindications for stimulation.

CONCLUSIONS

3 main conclusions emerged: (a) The main limitations for inclusion in brain stimulation trials of motor recovery were magnitude of UE motor impairments and stroke lesion characteristics, (b) most stroke patients could be stimulated with tDCS without safety concerns and (c) carefully tailored inclusion criteria could increase diversity in enrollment.Clinical Trial Registration-URL: http://clinicaltrials.gov. Unique identifier: NCT01007136.

Non-invasive brain stimulation as therapeutic approach for ischemic stroke: Insights into the (sub)cellular mechanisms

Although spontaneous recovery can occur following ischemic stroke due to endogenous neuronal reorganization and neuroplastic events, the degree of functional improvement is highly variable, causing many patients to remain permanently impaired. In the last decades, non-invasive brain stimulation (NIBS) techniques have emerged as potential add-on interventions to the standard neurorehabilitation programs to improve post-stroke recovery. Due to their ability to modulate cortical excitability and to induce neuroreparative processes in the brain, multiple studies have assessed the safety, efficacy and (sub)cellular mechanisms of NIBS following ischemic stroke. In this review, an overview will be provided of the different NIBS techniques that are currently being investigated in (pre)clinical stroke studies. The NIBS therapies that will be discussed include transcranial magnetic stimulation, transcranial direct current stimulation and extremely low frequency electromagnetic stimulation. First, an overview will be given of the cellular mechanisms induced by NIBS that are associated with enhanced stroke outcome in preclinical models. Furthermore, the current knowledge on safety and efficacy of these NIBS techniques in stroke patients will be reviewed.