P 223. A multielectrode cap for transcranial direct current stimulation (tDCS)

Introduction Many electrode montages for transcranial direct current stimulation (tDCS) are described in literature: attention must be paid on the correct positioning of the electrodes and on their geometry to obtain reproducible results. Also, to make tDCS even more simple and accessible to a large number of subjects, the electrode positioning should be easy for patients and their caregivers. Therefore, to guarantee safety during tDCS treatment any electrode system should protect the users from (i) incorrect placement of the electrodes over the scalp, (ii) wrong connection of the electrodes to the DC stimulator, and should ensure the proper pressure over the electrode to warrant the optimal impedance. Objective Design a system for correct and easily reproducible placement of tDCS electrode. Materials and methods From literature review and our experience in the clinic we have defined the design requirements for the new system. The system has to be composed by: a cap, an armband and a set of electrodes. Based on the numerical simulation of the current distribution near the electrodes, we designed a new electrode geometry to avoid ‘hotspots’ preventing dangerous current density and the resulting tissue damage. Results The cap is equipped with electrodes disposed according to the International 10–20 System and has an innovative structure characterized by ‘three lines of force’. This structure guarantee the correct strain over the entire scalp’s surface and the necessary pressure on the electrode under the electrical connections for the correct contact’s impedance. The shape of the electrode has not angles or vertex: this geometry avoids the insurance of ‘hotspots’. Moreover the electrode is made of inert materials, without any metal components and the internal sponge of the electrode is able to absorb a large quantity of saline solution. The cap has two locking system. With the first locking system the clinicians can block the electrode’s anchorages on the cap in placement different from the montage dedicated to the patient. With the second locking system the doctor can block the electrical connection of the cap in order to avoid the connection of the DC stimulator’s cable to the cap in a wrong placement without the underlying electrode. Conclusion We present a stimulating cap for tDCS that promises to be easy to use, to allow reproducible electrode placement and to avoid mistakes in stimulation polarity. Conflict of interest Elena Rossi is supported by “Dote ricerca”: FSE, Regione Lombardia and Newronika srl, a spin-off company of the Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico and the Universita degli Studi di Milano.