An implantable neurostimulation electrode assembly comprises a first electrode unit and a second electrode unit configured to be arranged in a side-by-side configuration. The first electrode unit includes a dielectric first paddle, a plurality of first electrodes carried by the first paddle, and a guideline. The guideline has a distal section affixed to the first paddle and a proximal section having a length configured to extend externally of a patient. The second electrode unit has a dielectric second paddle and a plurality of second electrodes carried by the second paddle. The second paddle is configured to travel along the guideline and contact the first paddle in the side-by-side configuration. As a result, the first and second electrode units of this embodiment can be passed percutaneously through the same percutaneous entry hole and assembled in vivo at the stimulation site to form a larger paddle-type electrode array without surgical implantation.
