Spiral ganglion neuron (SGN) degeneration is a candidate factor for reduced hearing outcomes in cochlear implant (CI) users. However, there is no procedure available to identify CI contacts close to focal SGN degeneration in human patients. In an animal model, we assessed the impact of focal SGN degeneration on electrical responsiveness and derived an electrophysiological marker for the presence, location, and size of such lesions. We introduced cochlear microlesions in 13 guinea pigs (six female) and recorded electrically evoked compound action potentials (eCAP) after 8-12 d. These were compared with recordings from controls (