OBSERVATIONS on sensory involvement occurring in the course of multiple (disseminated) sclerosis were made as early as 1835 by Cruveilhier,1 but it was not until 1905 that the association of trigeminal neuralgia with the disease was first reported.2,3 Since then it has been described by other observers among whose experiences Harris'4 is especially noteworthy. In his series of 2,083 cases of trigeminal neuralgia collected over a period of 25 years, the connection was noted in 68 patients. By contrast there were only two cases of tabes, two of Parkinson's disease, and only one of Friedreich's ataxia which led Harris to speculate on a possible connection between the two conditions. Although unsupported by postmortem evidence, his view was that the pain might be due to the presence of sclerotic patches within the pons and medulla in the neighborhood of the descending spinal root of the trigeminal nerve. Frazier,