a flex circuit having a trunk region that extends in a longitudinal direction and a plurality of branches that extend laterally from the trunk region, each of the branches having a free distal end and a proximal end that is connected to the trunk region, with a plurality of branches extending on at least one lateral side of the trunk region, the flex circuit having an inner skin-facing side and an outer side;

a plurality of electrode elements disposed on the inner side of the flex circuit along the branches of the flex circuit, each of the electrode elements having a conductive plate that is (a) connected to the flex circuit in an electrically conducting manner and (b) adapted to be positioned to face the skin of the patient;

a foam layer disposed on the inner side of the flex circuit, wherein the foam layer is configured to cover at least a portion of the trunk region of the flex circuit and at least a portion of the branches of the flex circuit, and leave the electrode elements uncovered;

a skin-level adhesive layer disposed on a skin-facing side of the foam layer; and

a top, covering layer disposed on the outer side of the flex circuit, the covering layer being sized to cover the branches of the flex circuit and to overlap spaces between the branches, the covering layer having adhesive on a skin-facing side thereof by means of which the covering layer can be adhered to an underlying surface through the spaces between the branches.