Non-invasive brain stimulation for improving gait, balance, and lower limbs motor function in stroke

I see nothing here that suggests they are solving the spasticity problem in walking.

Since 30% of survivors that have spasticity, they are screwed in walking recovery.

Non-invasive brain stimulation for improving gait, balance, and lower limbs motor function in stroke

• Jitka Veldema &
• Alireza Gharabaghi 

Journal of NeuroEngineering and Rehabilitation volume 19, Article number: 84 (2022) Cite this article

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Abstract

Objectives

This systematic review and meta-analysis aim to summarize and analyze the available evidence of non-invasive brain stimulation/spinal cord stimulation on gait, balance and/or lower limb motor recovery in stroke patients.

Methods

The PubMed database was searched from its inception through to 31/03/2021 for randomized controlled trials investigating repetitive transcranial magnetic stimulation or transcranial/trans-spinal direct current/alternating current stimulation for improving gait, balance and/or lower limb motor function in stroke patients.

Results

Overall, 25 appropriate studies (including 657 stroke subjects) were found. The data indicates that non-invasive brain stimulation/spinal cord stimulation is effective in supporting recovery. However, the effects are inhomogeneous across studies: (1) transcranial/trans-spinal direct current/alternating current stimulation induce greater effects than repetitive transcranial magnetic stimulation, and (2) bilateral application of non-invasive brain stimulation is superior to unilateral stimulation.

Conclusions

The current evidence encourages further research and suggests that more individualized approaches are necessary for increasing effect sizes in stroke patients.

Introduction

Each year, approximately 795,000 people experience a new or recurrent stroke [1]. Walking and balance disturbances are common post-stroke complications, affecting about two-thirds of stroke survivors [2]. These deficits are associated with worsened quality of life, impeded community reintegration [3], and an increased risk of falling [4]. The ability to walk independently is the most common rehabilitation goal after stroke [5]. However, about 50% of stroke survivors suffer from an impaired walking ability 6 months after current standard of care [2]. Other interventions are therefore needed to improve recovery. Thus, the development of innovative therapeutical strategies for improving balance and walking ability is one of the top research priorities in stroke rehabilitation [6]. Non-invasive neuromodulation methods such as repetitive transcranial magnetic stimulation (rTMS), transcranial direct/alternating current stimulation (tDCS/tACS) and trans-spinal direct current stimulation (tsDCS) can modulate neural processing and have thus the potential to counteract maladaptive neural plasticity after stroke and contribute to a better recovery [7, 8].

Neural background of walking and balance

Neuroimaging studies have shown that walking and balance are complex sensorimotor functions controlled by integrated cortical, subcortical, and spinal networks [9,10,11]. A single photon emission computed tomography study demonstrates bilateral activation within the primary sensorimotor area, supplementary motor area, basal ganglia as well as within the visual cortex, cerebellar vermis, and part of the left lower temporal lobe during walking [12]. Similarly, a positron emission tomography study shows a bilateral increase of cerebral blood flow within the primary sensory cortex, primary motor cortex and supplementary motor cortex as well as within the anterior part of the cerebellum during active and passive bipedal movement [13]. A recent meta-analysis indicates a key role of the brainstem, cerebellum, basal ganglia, thalamus, and several cortical regions during postural control [9]. Accordingly, another meta-analysis shows that the cerebellum, basal ganglia, thalamus, hippocampus, inferior parietal cortex, and frontal lobe regions are involved during balance tasks [14]. Importantly, the available data indicates that also a spinal network may be involved in postural balance and gait control [15]. E.g., multiple studies demonstrate that balance training induces suppression of H-reflexes [16]. Thus, it is conceivable that the application of non-invasive brain stimulation over several cortical regions as well as over the cerebellum, the brainstem and the spinal cord may be effective in the modulation of walking, balance and/or lower limbs motor function.

Stroke-induced changes of neural control during walking

Up to now, different neuroimaging techniques have been used to investigate the neural mechanism of walking disability and walking recovery in stroke patients. A large part of the available data demonstrates a stroke-induced disinhibition of the contralesional hemisphere with a shift of the between-hemispheric balance to the detriment of the affected hemisphere, as well as a correlation between normalization of neural processing and favorable motor recovery [17,18,19,20,21]. A diffusion tensor MRI demonstrates a between-hemispheric asymmetry in fractional anisotropy of the posterior limb of the internal capsule [18]. The shift of balance towards the non-lesioned hemisphere correlates with the amount of walking disability [18]. An optical imaging study shows a between-hemispheric imbalance of oxygenated hemoglobin level in the medial primary sensorimotor cortex that is greater in the unaffected hemisphere than in the affected hemisphere. A reduction of this asymmetry is associated with a favorable gait recovery [19]. A TMS study shows an interhemispheric asymmetry of corticomotor excitability of the legs to the detriment of the affected hemisphere, as well as a correlation between the reduction of this asymmetry and a favorable motor outcome [20]. Another TMS trial reveals increased connectivity between the contralesional hemisphere and the affected lower limb, which correlated with the amount of walking disability [18]. A diffusion-weighted MRI shows that the higher the anatomical connectivity between the ipsilesional M1 and the (a) cerebral peduncle, (b) thalamus, and (c) red nucleus, the better is the lower limb motor performance [21]. Furthermore, stroke-related disturbances of the spinal system were detected, as well as its relationship to gait disability. In fact, stroke patients show an increase of the H-reflex, in comparison to healthy subjects [22], and its normalization to be associated with a successful motor recovery of the walking ability [23].

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