Medical electrode patch. The post-ear electrode patch is a sheet electrode attached behind the ear. Its main function is to transmit current through skin and tissue to achieve therapeutic purposes. This electrode patch is often used in various electrotherapy, such as transcranial microcurrent stimulation therapy (CES). In these therapies, the postauricular electrode patch is usually used with other electrodes, such as forehead or limb electrodes, to form a complete current loop.