In a patient affected by locked-in syndrome, because of a lesion of the caudal-ventral pontine tegment, we recorded event-related potentials (ERPs) to an acoustic odd-ball paradigm. We did not record N2 and P3 components in the 50 days following the acute lesion although the patient was able to understand the task and communicate with blinking. 55 days after the acute lesion, N2 and P3 reappeared on scalp derivations. This findings suggest that brainstem structures are involved in P3 or N2-P3 generation.