[Benign forms of multiple sclerosis].

It is still difficult, in 1991, to evaluate precisely the position occupied by benign forms of multiple sclerosis (MS) in the natural history of the disease. The reality hidden behind the adjective "benign" varies from one author to another, and the estimated frequency of these forms is not the same when one refers to epidemiological studies on whole populations or to clinical studies in major hospitals. There is, however, no doubt that benign MS does exist, since about 10% of MS patients will suffer, throughout the whole duration of the disease (over 30 years), from no more than moderate disablement with few repercussions on their social and professional life. These are patients in who MS began when they were 20 to 30 years' old and evolved by episodes rather than progressively and whose main symptoms are optic neuritis and sensory disorders without pyramidal or cerebellar deficit. Nevertheless, these cases are not easy to recognize a priori: there is no paraclinical examination that can predict a benign course in the long term, and an MS which has long been benign may become worse at any moment.