Transcranial Electrical Nerve Stimulation for Dementia

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Overview of Trans-cranial Electrical Nerve Stimulation[edit | edit source]

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.[1] Rcently, Because of its potential ability to alter brain neuronal excitability and connectivity TES is becoming a topic for non-pharmacological management of various cognitive related conditions and this concept is still under research for effectiveness.[2] Transcranial Stimulation and is one of the techniques used to stimulate the brain of a person with dementia.[3] and recent evidence had shown that CES alone or in combination with physiotherapy improves certain functional activities in person with possible cognitive impairment[4], Yet, trans-cranial electrical nerve stimulation is not a common practice among physiotherapists who are one of the experts in dementia management. Accordingly, this paper will provide information on the CES method of application to stimulate the brain of a person with dementia.

Dementia (Major Neurocognitive disorder)[edit | edit source]

DSM-5 details on the definition and diagnosis of neurocognitive disorders.[5] Dementia, now referred to as a major neurocognitive disorder under DSM-5 for neurocognitive disorder, is an impairment in one or more cognitive domains with impaired functional status[5], which is of concern to both patient and patient relative. A cognitive impairment without significant effect on a person with dementia's  activities of daily living is considered mild neurocognitive impairment.Neuropsychological and behavioral characteristics such as anxiety, depression and sleep disturbances are prominent features of dementia.[6][7] Such symptoms, including neurocognitive dysfunction, may be enhanced by using transcranial electrical nerve stimulation.[3][8][9].

Mechanism of Trans-cranial electrical nerve stimulation[edit | edit source]

Non-Invasive brain stimulation (trans-cranial electrical nerve stimulation ) main modalities is trancranial (direct and alternating) and this will be expansiate in this write up.[10] Other forms of non-invasive brain stimulation includes TMS,Transcranial magnetic stimulation and Repetitive transcranial magnetic stimulation,rTMS.[11] Transcranial alternating current stimulation, tACS, delivers an alternated sinusoidal current at a specific frequency while transcranial direct current stimulation,TDCS, stimulates or inhibit brain activity through use of two small electrodes placed on the head deliver a constant low level of electric current. In 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.

The two main modalities in TES are the tACS and tDCS. In TES, the tDCS uses a constant current,direct current and tACS uses a charge.balance. Physiologically, the mechanism of action of these two modalities are different. The tDCS is believe to alter neuronal excitability by excitatory or inhibitory action and consequently modulatiing synaptic plasticity (long term potentiation or long term depression). In tACS, specific sine-wave stimulation waveforms interact with endogenous brain oscillations to alter neuronal plasticity for desired outcome.[12]

Cognitive Impairment Assessment[edit | edit source]

Evaluating a person with dementia requires neuropsychological assessment tools. Among these tools, the most common universally used is Mini Mental State Examination[13] and for functional status, Functional Activities Questionnaire (FAQ) for older adults might be used[14]. In addition, these tools can be used to monitor the progress of the intervention of a person with major neurocognitive impairment.

Trans-cranial Electrical Nerve Stimulation (CES) intervention[edit | edit source]

Scholars argued that tES could stimulate the brain and improve both cognitive impairment and neuropsychological characteristics of the dementia.[3] However, the use of electrotherapy modalities such as tES requires a skin sensation test to determine whether the intervention is appropriate. Furthermore, the application of CES requires a number of parameters  and this depend  on the objectives to be achieved[9] [15]. Moreno-Duarte,[9] argued that low-level transcranial electrical nerve stimulation is the most documented intensity level of CES application and four methods exist for this: transcranial direct current stimulation (tDCS), transcranial pulsed current stimulation (tPCS), transcranial alternating current stimulation (tACS) and transcranial random noise stimulation (tRNS) (see Figure 1 for more information). Although there is still some controversy regarding the use of CES among people with dementia, there is support for the evidence that the use of CES combined with physiotherapy or not improve cognitive, physical and behavioral characteristics of a person with dementia.[4][16]

Figure 1

TES in Physiotherapy Practice for Brain Stimulation[edit | edit source]

Transcranial direct current stimulation (tDCS) is a widely reported type of cranial electrical nerve stimulation in Physiotherapy.[18]. Schabrun[18] noted that with different TENS parameters for different conditons, tDCS could improve both neurological and musculoskeletal conditons. Also, Yotnuengnit et al., [4] reported that tDCS improves gait speed and step length among patients with Parkinson disease. While CES may be beneficial in stimulating a person with a brain dementia, further studies are needed in patients with cognitive impairment to determine the efficacy of this intervention.

References[edit | edit source]

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  3. 3.0 3.1 3.2 Cameron MH, Lonergan E, Lee H. Transcutaneous electrical nerve stimulation (TENS) for dementia. Cochrane Database of Systematic Reviews. 2003(3).
  4. 4.0 4.1 4.2 Yotnuengnit P, Bhidayasiri R, Donkhan R, Chaluaysrimuang J, Piravej K. Effects of transcranial direct current stimulation plus physical therapy on gait in patients with Parkinson disease: a randomized controlled trial. American journal of physical medicine & rehabilitation. 2018 Jan 1;97(1):7-15.
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