Cranial electrotherapy stimulation (CES)

Cranial electrotherapy stimulation (CES) was developed from Electrsleep which

mechanism was based on peripheral nerve stimulation to induce neurotransmitter level change central nervous system. Instead of using “transcranial” as term of description,

CES used “cranial” as its term which emphasize the current not flow through the scalp¹.

The peripheral stimulation mechanism focuses on the stimulus transmit into CNS with

change of antinociception reaction. The pathway of the stimulus may go from cranial

nerve I-III and VIII to activate of brainstem center. Some of the CES emphasize the

electrode need to place on bilateral eyes to induce peripheral pathway to influence

central nervous system.

Second potential mechanism was CES may induce release of neurotransmitter.

CES also have good effects on biological clock of brain which controlled in

hypothalamic suprachiasmatic nucleus (SCN) in brain stem²¹. The serotonin level and

noradrenaline level was also increase after CES intervention. Base on previous

physiological review, the serotonergic system was more response to stimulation with

10, 20 and 100Hz. TCET was one type of CES which was asymmetric biphasic current

with equal charge. When TCET applied on rat, the dopamine and norepinephrine level

were significant increase. The stimulation seems to induce synthesis of

neurotransmitter in midbrain or hypothalamus. No neurochemical response was found

in hindbrain neurotransmitter synthesis center which indicate the neurotransmitter

synthesis response was localized not whole brain.⁹

Third potential mechanism was alternating current may interruption or

disturbance ongoing cortical activity. Previous study also showed CES can alter EEG which showed lower shift median frequency of α wave. The frequency of CES was set

at 0.5Hz and 100Hz. higher frequency has more obvious effect on interruption of α

wave. Reduction median frequency of α wave was associated with more relaxation

status¹⁰. α wave was also related to awake and sleep status change. Significant desynchronizing of α wave was found in sleep status²⁵.

2.3.1 Research in Animal Model

Some animal studies reveal how functional or structural change of the neural

tissue after stimulated by alternating current. In hippocampus cell, high frequency

electrical stimulation would induce long tern potentiation (LTP) which was long last

change of synaptic efficiency. Low frequency electrical stimulation do not induce LTP

liked response or even resulted in long term depression. Recent study overthrows this

concept and indicated that low frequency electrical stimulation (1Hz) would also

produce LTP response with specific afferent system. The 0.5 Hz alternating pulse

current induce CA1 LTP like response. However, low frequency stimulation on CA3

was ineffective²⁶.

Whether the AC current actually can influence neuron is controversial especially

when charge was balance. Transcranial electrostimulation treatment (TCET) was

biphasic current with pulse which charge was balance. In the hypothalamic level of the

rat, TCET significantly enhance dopamine and norepinephrine synthesis. In mid-brain

of the rat, the serotonin and dopamine significant enhance synthesis. Although the

dopamine and norepinephrine synthesis increase, the turned over rate not change which

detected by measured the metabolite of neurotransmitter.

2.3.2 Research in Human Model

CES commonly used as treatment of depression, anxiety, insomnia, pain, migrant

headache, pain of fibromyalgia and sleep-awake cycle disorder. Few of clinical trials

focus on the rehabilitation effect of CES on movement disorder. Most of experiments

of CES were focus on cognitive, biological clock, psychological problems. Malden’s

study in 1985 indicated that the CES can enhance occupation therapy effect on gross

motor performance in severe cerebral palsy children. Actually, the evidence level of

motor function related study was not strong. CES also facilitates sensory motor

integration in children. In Okoyey’s in 1986, the motor accuracy and hand function

significantly improved in minimal cerebral palsy children²⁷.

CES was also effective for pain relief. Most of the studies focus on how

neurotransmitter of nociception system affected by CES. In another point of view that

patients with chronic degenerative joint pain syndrome show abnormal peak and

unsmooth pattern in EEG spectrum curve in bilateral frontal area. In contrast, normal

healthy subject show relative more smooth of frequency spectrum curve than chronic

degenerative joint pain patient. Both patient with pain and healthy subject received 20

mins of microcurrent stimulation with 0.5 Hz biphasic rectangular pulse current. The

electrode placed on bilateral trapezius or earlobe. The electrode placed on trapezius

muscle which was trying to induce neurotransmitter level change through cervical

nerve. After CES intervention, the unsmooth pattern of EEG spectrum significant

improved which was near normal spectral curve. Furthermore, pain score of patient

also significant decrease^28,29. Though the cortical electrical oscillation status change

after CES intervention, the effect still believed derived from neurotransmitter modulate

effect in subcortical area.

Another study compared the effects of high frequency CES and low frequency on

EEG spectral curve. Low frequency CES (0.5Hz) showed significantly downshift of mean frequency of α band. High frequency CES (100Hz) showed significant downshift

of mean and median α band frequency. α band frequency downshift was more related

to relaxation status of subject which indicate the CES facilitation relaxation state. After 100Hz CES intervention the power fraction of β band frequency significant decrease. β

band frequency was more related to stress, arousal, problem solving state. It seems that

higher frequency of CES was more effective in brain oscillation modulation.³⁰ Another

fMRI study reveal that CES stimulation disrupted cortico-cortical network such as

connectivity between frontal lobe and parietal lobe¹⁰. General hemodynamic response

of specific task was less in CES stimulation condition. Based on these findings,

changes pattern of power spectral curve after CES was suspected the results of changes

of neurotransmitter level in subcortical area.