An implantable medical device for implantation in the head of a patient. The implantable medical device has a plurality of interconnected modules one or more of which are covered by an overmold and one or more of which are partially covered by the overmold. The module(s) covered by the overmold may be implanted between the cranium and scalp, while the module(s) partially covered by the overmold may be placed at least partially into a recess in the cranium.