Open AccessMinimal Heating at the Skin Surface During Transcranial Direct Current Stimulation
Author(s) -
Khadka Niranjan,
Zannou Adantchede L.,
Zunara Fatima,
Truong Dennis Q.,
Dmochowski Jacek,
Bikson Marom
Publication year - 2018
Publication title -
neuromodulation: technology at the neural interface
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 60
eISSN - 1525-1403
pISSN - 1094-7159
DOI - 10.1111/ner.12554
Subject(s) - transcranial direct current stimulation , current (fluid) , stimulation , physical medicine and rehabilitation , neuroscience , medicine , psychology , biomedical engineering , electrical engineering , engineering
Objective To assess if transcranial direct current stimulation (tDCS) produces a temperature change at the skin surface, if any change is stimulation polarity (anode or cathode) specific, and the contribution of passive heating (joule heat) or blood flow on such change. Material and Methods Temperature differences (Δ T s) in an agar phantom study and an in vivo study (forearm stimulation) including 20 volunteers with both experimental measures and finite element method (FEM) multiphysics prediction (current flow and bioheat) models of skin comprising three tissue layers (epidermis, dermis, and subcutaneous layer with blood perfusion) or of the phantom for active stimulation and control cases were compared. Temperature was measured during pre, post, and stimulation phases for both phantom and subject's forearms using thermocouples. Results In the phantom, Δ T under both anode and cathode, compared to control, was not significantly different and less than 0.1°C. Stimulation of subjects resulted in a gradual increase in temperature under both anode and cathode electrodes, compared to control (at t = 20 min: Δ T anode = 0.9°C, Δ T cathode = 1.1°C, Δ T control = 0.05°C). The FEM phantom model predicted comparable maximum Δ T of 0.27°C and 0.28°C (at t = 20 min) for the control and anode/cathode cases, respectively. The FEM skin model predicted a maximum Δ T at t = 20 min of 0.98°C for control and 1.36°C under anode/cathode electrodes. Conclusions Taken together, our results indicate a moderate and nonhazardous increase in temperature at the skin surface during 2 mA tDCS that is independent of polarity, and results from stimulation induced blood flow rather than joule heat.