A shielded electrode assembly for sensing electrical signals within a nerve is disclosed. The assembly comprises a generally tubular, electrically insulating shield body, which may be reversibly secured to the nerve. An electrically conducting mesh is positioned on at least a portion of an outer surface of the shield body, defining a region of the assembly within which external electromagnetic radiation is significantly attenuated. The conducting mesh is formed by photolithography, providing substantially precise control over the mesh aperture and thus the frequency of radiation which is shielded. A plurality of electrodes are placed within the shielded region and configured so as to contact the nerve. This design allows the electrodes to sense nerve signals within an environment which is at least partially shielded from electromagnetic radiation, facilitating nerve sensing with reduced need for filtering or signal processing.