A 49-year-old man with definite multiple sclerosis suffered an episode of right-sided trigeminal neuralgia (TN) of two weeks' duration, unaccompanied by any other clinical symptoms or signs of exacerbation. Serial evoked potentials, obtained before, during, and after TN, demonstrated developing abnormalities in brain-stem auditory evoked potentials from the right ear that disappeared in a delayed fashion after the clinical symptoms of TN had subsided. This rare combination of clinical and electrophysiologic abnormalities suggests a pontine demyelinating plaque involving the right trigeminal sensory root and the right lateral lemniscus.