1. An implantable neurological probe comprising: a cylindrical member having a distal end, a proximal end, and an internal lumen; a flexible planar substrate comprising: a first insulative layer, a microelectrode film, an extension including a plurality of wire lead contacts, a plurality of microelectrode elements disposed on an outer surface of the microelectrode film, a plurality of conductive traces to selectively couple the plurality of microelectrode elements to the plurality of wire lead contacts, and a plurality of wires to electrically couple the plurality of wire lead contacts to a proximal end of the probe; wherein the microelectrode film of the flexible planar substrate is coupled to an outer surface of the cylindrical member with the extension of the flexible planar substrate extending in the internal lumen toward the proximal end of the cylindrical member, and wherein the plurality of wire lead contacts are disposed within the internal lumen such that at least a portion of the extension of the flexible planar substrate is disposed in the internal lumen.