Safety Study Based on Transcranial Electrical Stimulation in Chile: a Case Series Study

Transcranial electrical stimulation (tES) is a neurophysiological technique capable of modulating the excitability of the neuronal tissue of the central and peripheral nervous system through the application, for a finite time length, of an electrical field. This electric field is generated by the application of weak electrical currents through the scalp and into the brain. It has been demonstrated in recent years that the technique is safe and beneficial if used within the known bounds of intensity, density and duration.

The tES technique is classified into three types according to the waveform of the stimulation current that is applied: Transcranial direct current stimulation (tDCS),Transcranial Alternating Current Stimulation (tACS) and Transcranial random noise stimulation (tRNS). Additionally, the Sham mode can be used for controlled experiments.

TDCS is a neuromodulatory technique that delivers low-intensity, direct current to cortical areas facilitating or inhibiting spontaneous neuronal activity. In general, the current is injected into the brain (anodal stimulation) over a cortical region leading to excitatory effects; and collected from the brain (cathodal stimulation) leading to inhibitory effects. tDCS produces short term effects on neuronal excitability, and long lasting plastic after/effects involving synaptic modification.

Research has shown that applying anodal tDCS to the non-dominant motor cortex can improve motor performance for the non-dominant hand, presumably by means of changes in synaptic plasticity between neurons. Other studies suggest improvement on cognitive functions such as memory, language, and attention after a tDCS program.

TDCS secondary effects have been measured in several studies. The most frequent secondary effects described in literature are a mild tingling sensation, moderate fatigue, itching sensation, slight burning and mild pain sensation under the electrodes during the stimulation. A visual sensation, associated with switching on and off the stimulation, have been also described. Less frequent are the difficulties in concentrating, headache, felt nervous or overexcited and nausea after the stimulation.