An expandable electrode cuff of an implantable stimulation system, comprising: a base member extending from a first side wall to a second side wall and having a top wall and a bottom wall; a first flange member; a second flange member; a third flange member, wherein: the third flange member is arranged to extend from a proximal end along the first side wall to a third distal end positioned above the first side wall; the second flange member is arranged to extend from a proximal end along the second side wall to a second distal end; and the first flange member is arranged to have a proximal end fixedly engaged against the third flange member and to extend to a first distal end, wherein: the first flange member is arranged to extend over both the top wall of the base member and the second flange member, the second flange member is arranged to extend over the top wall of the base member, and the first, second, and third flange members are arranged to be biased to be in a fully-engaged position in which the second distal end of the second flange member is positioned adjacent to and engaged against the third distal end of the third flange member at a location along the first flange member so that the first flange member, the second flange member, and the third flange member form a lumen. a base member extending from a first side wall to a second side wall and having a top wall and a bottom wall; a first flange member; a second flange member; a third flange member, wherein: the third flange member is arranged to extend from a proximal end along the first side wall to a third distal end positioned above the first side wall; the second flange member is arranged to extend from a proximal end along the second side wall to a second distal end; and the third flange member is arranged to extend from a proximal end along the first side wall to a third distal end positioned above the first side wall; the second flange member is arranged to extend from a proximal end along the second side wall to a second distal end; and the first flange member is arranged to have a proximal end fixedly engaged against the third flange member and to extend to a first distal end, wherein: the first flange member is arranged to extend over both the top wall of the base member and the second flange member, the second flange member is arranged to extend over the top wall of the base member, and the first, second, and third flange members are arranged to be biased to be in a fully-engaged position in which the second distal end of the second flange member is positioned adjacent to and engaged against the third distal end of the third flange member at a location along the first flange member so that the first flange member, the second flange member, and the third flange member form a lumen. the first flange member is arranged to extend over both the top wall of the base member and the second flange member, the second flange member is arranged to extend over the top wall of the base member, and the first, second, and third flange members are arranged to be biased to be in a fully-engaged position in which the second distal end of the second flange member is positioned adjacent to and engaged against the third distal end of the third flange member at a location along the first flange member so that the first flange member, the second flange member, and the third flange member form a lumen.