Safety – Transcranial direct current stimulation tDCS

Excellent overview article on tDCS from University of Munich who have a research group devoted to Transcranial brain stimulation and neuroplasticity.

Safety of the method
Several studies have been performed on the safety of tDCS and on side effects and have resulted in clear recommendations on its safe use. There is general agreement that if attention is paid to recommendations concerning contraindications and stimulation parameters, tDCS is a well tolerated method with minimal side effects Nitsche et al. 2003, Fregni et al. 2006, Iyer et al. 2005.
The physiological changes involve the modulation of spontaneous neuronal activity through polarity-specific shifts of the resting membrane potential in the direction of de- or hyperpolarisation. The direction of the change is governed by the direction of current flow, the spatial orientation of the neuron, the type of neuron and the total charge. This underlies the possible complication of inducing an epileptic seizure. In accordance with the safety protocol from Nitsche and Paulus 2000, the stimulation charges used here lie far below the charges necessary to trigger a seizure. Even a continuous stimulation just below the energy threshold for triggering a seizure was associated with only a 40% increased cortical excitability compared with baseline. Studies on the question of whether neuronal damage can be observed after tDCS and whether structural changes occur in the brain revealed no indications of damaging effects of tDCS. Thus, levels of neuron-specific enolase NSE, a marker for neuronal destruction, were not increased after tDCS Nitsche et al. 2003 and pathological changes could not be found in either contrast-enhanced MRT or in EEG Nitsche 2003.
Persistent disorders of motor and cognitive abilities have not been found. Electrically induced local muscle contractions during the stimulation can be unpleasant for the person undergoing tDCS. The electrical stimulation causes irritation of the scalp lasting just a few seconds, which has been described as more or less painful tingling and pulling Fregni et al. 2006. Cortical tissue damage has not been found, even after high stimulation intensities and frequencies. Stimulation with electrodes on the scalp could indeed result in a chemical reaction and in burning of the skin tissue. However, the risk of a skin burn is minimised if sponge electrodes soaked in salt water are used, in accordance with the safety protocol of Nitsche and Paulus 2000.
Fregni et al. did not describe any side effects in their studies Bip Disorders 2006, Clin Neurophysiol 2006, Depr and Anx 2006; the treatment was well tolerated by all the patients.

via Transcranial direct current stimulation tDCS.