Transcranial Electrical Nerve Stimulation for Dementia

Original Editor - Tolulope Adeniji

Top Contributors - Tolulope Adeniji, Kim Jackson, Lucinda hampton, Candace Goh, Rishika Babburu, Angeliki Chorti and Pacifique Dusabeyezu

Overview

Transcranial electrical nerve stimulation (tES) or Cranial Electrical Nerve Stimulation, CES, is a non-invasive brain stimulation where brain activity is excited or inhibited by application of a low voltage constant or alternating currents to the human brain via scalp electrodes.

Image 1: tES administration. A subject (front) sits on a sofa relaxed, and a researcher (behind) controls the tDCS device (a). A head strap (d) for convenience and reproducibility, and also use a rubber band (e) for reducing resistance

The tES is a promising tool in rehabilitation, based on the growing evidence that delivery of current to specific brain regions can promote desirable plastic changes. The tES is becoming a topic for non-pharmacological management of various cognitive related conditions and this concept is still under research for effectiveness.

• The tES is one of the techniques used to stimulate the brain of a person with dementia.
• Recent evidence had shown that tES alone or in combination with physiotherapy improves certain functional activities in person with possible cognitive impairment
• The tES is not a common practice among physiotherapists who are one of the experts in dementia management. Accordingly, this paper will provide information on the tES method of application to stimulate the brain of a person with dementia.

Dementia (Major Neurocognitive disorder)

Dementia is an impairment in one or more cognitive domains with impaired functional status, which is of concern to both patient and patient relative. Neuropsychological and behavioural characteristics such as anxiety, depression and sleep disturbances are prominent features of dementia. These symptoms, including neurocognitive dysfunction, may be enhanced by using transcranial electrical nerve stimulation..

Mechanism of Transcranial electrical nerve stimulation

Non-Invasive brain stimulation (transcranial electrical nerve stimulation ) main modalities are of different type and in this write up direct and alternating current type of trans-cranial electrical nerve stimulation mechanism will be discussed.

• Transcranial alternating current stimulation, tACS, delivers an alternated sinusoidal current at a specific frequency. In tACS, specific sine-wave stimulation waveforms interact with endogenous brain oscillations to alter neuronal plasticity for desired outcome.
• Transcranial direct current stimulation, tDCS. The tDCS is believed to alter neuronal excitability by excitatory or inhibitory action and consequently modulating synaptic plasticity (long term potentiation or long term depression).

Aside the direct and alternating current type of trans-cranial electrical nerve stimulation, It is important to highlight on some of the other existing forms of the non-invasive brain stimulation, which include:

1. Transcranial magnetic stimulation (TMS) - an electromagnet placed on the scalp generates magnetic field pulses that can activate axons and cause them to fire action potentials. For repetitive transcranial magnetic stimulation, it uses repeated application of TMS pulses for modulating brain activity.
2. Repetitive transcranial magnetic stimulation, rTMS. - which uses repeated application of TMS pulses for modulating brain activity.

Cognitive Impairment Assessment

Evaluating a person with dementia requires neuropsychological assessment tools. Among these tools, the most common universally used is Mini Mental State Examination(MMSE) and for functional status, Functional Activities Questionnaire (FAQ) for older adults might be used. And these assessment tools, the MMSE and FAQ can as well used tools to monitor the progress of the intervention of a person with major neurocognitive impairment.

TES in Physiotherapy Practice for Brain Stimulation

Promising findings suggest that tDCS may be a useful standalone treatment or a helpful complement to other physiotherapy treatments in managing chronic pain and neurological conditions.

However,

• There are only a small number of heterogeneous studies.
• There is a need of further studies that will contribute to the current studies evidence in terms of tDCS parameters, long-term follow-up and different pathological populations. This will aid in determining tDCS clinical efficacy.
• It is of importance to note that while there are evidences pointing to potential benefits of tDCS for dementia population it's clinical application in physiotherapy practice still needs to be extensively studied.

tDCS in stroke rehabilitation:

• In a randomised controlled trial conducted by Pires and colleagues, it was concluded that five tDCS sessions are sufficient to augment the effect of standard physiotherapy on upper limb function recovery in chronic post-stroke patients, and ten sessions resulted in greater gains .
• In the study conducted by Garrido and colleagues, they concluded that combining modified CIMT with bihemispheric tDCS in patients hospitalised with acute to subacute stroke allows us to maximise the motor and functional recovery of the paretic upper limb in the early stages and independence in ADL, maintaining the effects over time .
• In chronic stroke patients with severe hemiparesis of the upper limb, it was found that combined tDCS and virtual reality-based paradigm provided not only greater but also clinically meaningful improvement in the motor function (and similar sensory effects) in comparison to conventional physical therapy .
• Current findings suggest that tDCS combined with Robotic Therapy (RT) does not improve upper limb function, strength, spasticity, functional independence or velocity of movement after stroke . However, tDCS may enhance the effects of RT alone for lower limb function. tDCS parameters and the stage or type of stroke injury could be crucial factors that determine the effectiveness of this therapy.