An electrophysiological follow-up was performed in a rare case of subacute sclerosing panencephalitis (SSPE) that from the vegetative stage had an extremely favourable course, lasting 4 years, in which clinical conditions passed, according to the Risk and Haddad scale, from stage 3 to stage 1. In this period of time, 5 CT scans and a series of EEGs, visual evoked potentials (VEPs) and brainstem auditory evoked potentials (BAEPs) were performed to investigate the correlation between clinical course and electrophysiological diagnostic data. The results showed a significant improvement in diagnostic results, directly correlated with the remission of clinical symptoms. Electrophysiological signs of improvement in VEPs were obtained before observable improvement was seen on CT scans. These results indicate that an accurate electrophysiological study (through cerebral evoked potentials) has an important role in investigating suspected cases of SSPE, in following the clinical evolution of this disease and providing prognostic data.