Clinically isolated syndromes with no further disease activity suggestive of multiple sclerosis at the age of population life expectancy.

The proportion of patients with clinically isolated syndrome (CIS) reported to convert to clinically definite multiple sclerosis varied between 30 and 75%. We studied the lifetime probability of remaining in the "CIS only" condition. The study was based on the longitudinally followed Gothenburg 1950-1964 incidence cohort (n = 306). Survival analysis revealed that 17.8% of 236 attack onset patients remained "CIS only". Patients with afferent (optic and sensory) symptoms had a better prognosis with approximately 30% of these patients remaining "CIS only". Patients who had experienced no relapse during the first 25 years remained "CIS only" for the subsequent 25 years of follow-up.