Method of fabricating a stimulation lead for applying electrical pulses to tissue of a patient

A method of fabricating a stimulation lead comprises: providing a central insulator member; helically wrapping a plurality of conductors about the member, by arranging the plurality of conductor wires in groups with an inter-group spacing that is larger than an inter-conductor spacing within each group; providing an outer insulator layer to form an intermediate lead body assembly; forming a lead body by heating polymer material of the intermediate lead body assembly to cause insulative material of the lead body to form a solid, fused cylindrical body about the plurality of conductors, which comprise a first conductor, a last conductor, and inner conductors between the first and last conductor, wherein the first and last conductor comprise respective helix diameters that are smaller than the helix diameters of the inner conductors; and forming a plurality of electrodes and terminals on the lead body that are electrically connected through the plurality of conductors.