Combined Effects of Focal Muscle Vibration and tDCS on Motor Recovery in Stroke

A stroke is a medical condition characterized by a sudden, localized, loss of neurological function resulting from damage to the blood vessels in the central nervous system. It is a prevalent condition globally and leading cause of disability impairing motor function and significantly impact daily activities and work. 26% of individuals with stroke have a disability in ADLS and 50% have motor impairment gait disorder contribute to 20 to 30%. Spasticity 25%-40% which ultimately affect the quality of life of patients.

Spasticity arises from central nervous system damage where the loss of cortical neurons reduces descending inhibitory control over the spinal cord, affecting the balance between inhibitory and excitatory inputs leading to disinhibition of spinal reflexes causing hyperexcitability of stretch reflexes increase H reflex activity and impaired reciprocal inhibition.Fastest city interacts with weakness resulting in disabling motor impairments and complex complication like muscle contractor motor dysfunction and plastic paint which negatively impacts on patients quality of life.

Noninvasive brain stimulation (NIBS) has been seen more common in rehabilitation setting as an add on therapy to conventional rehabilitative treatment. The main goal of NIBS is to create neuromodulation by inhibiting or activating neural activity in the targeted cortical region. There are different modalities used for NIBS most widely used are transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS). tDCS involves a small current to the scalp aiming to modulate cortical excitability. Typical configuration of tDCS are the anode electrode place over the brain area of interest aiming to increase excitation and the cathode electrode placed as a reference, over contra lesional hemisphere aiming to decrease excitability and all electrode taste as a reference such as if she does not supra orbital region. In stroke recovery tDCS is often used to either enhance excitability in the lesioned hemisphere or suppress in the non-lesioned hemisphere to rebalance neural activity. The core concept of tDCS is operating on a simple principle, i.e. the positive terminal of the battery also referred to as the anode is connected to one special location on the head and the negative terminal or cathode is attached at the other end of the head. An electromotive force is generated between these two contact points on the head that creates a potential difference. This difference push positively charged ions that are potassium, sodium and calcium away from the anode towards the cathode this when way neurons that are located under the anode get a boost for excitation and at the same time inhibition occurs at the cathode and that's how whole brain activity is modulated.

Another intervention strategy that has potential for sustainable stroke rehabilitation is the use of mechanical vibration as a therapeutic intervention known as vibration therapy. Focal vibration (FV) reduces muscles spasticity, facilitate muscle contraction and stimulates the proper system to obtain efficient motor control during functional activities. In FV, mechanical vibrations are applied to localized muscles generally the muscle belly or the tendon on the affected side. The suggested mechanism of action of focal vibration on spasticity is depression of the H-reflex within the spinal motor neuron and reciprocal inhibition between the agonist and antagonist muscles.

A study was done aimed to assist the current evidence on the effect of tDCS on upper limb motor function and identified evidence suggest that tDCS has a superior effect in improving function of upper lamp in patient who had a stroke. In 2019, meta-analysis was done to explore the effect of tDCS on different stages of stroke (acute, sub-acute, chronic) and result show that tDCS had a significant effect in the patient of chronic group. Stronger connectivity of ipsilesional and the parietal cortex and contra lesional frontotemporal cortex was found to be associated with an increase in cortico spinal excitability following the anodal tDCS in chronic stroke survivors. A meta-analysis of multiple session reviewed how tDCS parameters influence upper limb function and demonstrate that tDCS applied during therapy yield significant results.