An electrical feedthrough assembly according to the invention can be used as a component of an implantable medical device (IMD) and/or or electrochemical cell. An IMD includes implantable pulse generators, cardioverter-defibrillators, physiologic sensors, drug-delivery systems, etc. Such assemblies require biocompatibility and resistance to degradation under applied bias current or voltage. In some forms of the invention, such assemblies are fabricated by using electrically common, multiply-interconnected electrical pathways including metallized vias and interlayer structures of conductive metallic material within bores and between ceramic layers. The layers are stacked together and sintered to form a substantially monolithic dielectric structure with at least one electrically common embedded metallization pathway extending through the structure. The metallization pathway reliably conducts electrical signals even when exposed to body fluids and tissue and providing electrical communication between internal IMD circuitry and active electrical components and/or circuitry coupled to the exterior of an IMD.