A biomedical conductor assembly adapted for at least partial insertion in a living body. The conductor assembly includes a plurality of the first electrical conductors each covered with an insulator and helically wound in a first direction to form an inner coil with a lumen. A plurality of second electrical conductors each including a plurality of un-insulated wires twisted in a ropelike configuration around a central axis to form a plurality of cables. Each cable is covered with an insulator and helically wound in a second opposite direction forming an outer coil in direct physical contact with the inner coil. The inner and outer coils are covered by an insulator. A method of making the conductor assembly and implanting a neurostimulation system is also disclosed.