A catheter assembly for intracranial treatment of a patient is disclosed. The assembly comprises outer and inner catheters. The outer catheter has an exterior surface, an inflatable balloon mounted upon the exterior surface, at least one element distal to the balloon, at least one aperture and a lumen. The inner catheter is sized to be received within the lumen and has a passageway extending between a proximal end and at least one port. The lumen is adapted to guide the inner catheter to the desired tissue region in the brain. Each element is adapted to monitor brain activity within the tissue region, to electronically stimulate the tissue region, or to provide information on a precise position of the element when the element is entirely within the brain. The elements are mounted proximal to the distal end of the outer catheter upon the exterior surface of its distal portion. The assembly can facilitate the administration of drugs to the tissue region or the removal of fluid from the brain through the inner catheter.