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.