[Epidemiology and clinical evolutionary aspects of multiple sclerosis in Navarra]

In the present study 84 patients with the diagnosis of multiple sclerosis were identified as living in Navarra on the date of prevalence (December 31, 1986). The raw yearly incidence rate was 0.49/100000, which is similar to that in Mediterranean countries. A significant increase of this rate was found between 1951 and 1986, which was interpreted as a consequence of higher economic status and/or progressive industrialization. The raw prevalence rate was 16.4/100000 and age-specific prevalence was 26.5. Therefore, Navarra is a medium risk area for MS. Mean age at onset was 29.3 years, with a significant female predominance. In addition, MS presented earlier in females. The relationship between MS and latitude of the residence area was confirmed. The most common presenting symptoms were motor (paresia) and sensory (paresthesia). Cerebrospinal fluid was abnormal in 86.5% of patients, evoked potentials (mostly visual) in 85.9%, and magnetic resonance in 100%. Demyelinizing signs were detected with CT in 29.4% of patients. The diagnostic criteria of the Boston University Workshop were highly reliable. The most common evolutive pattern was the pure remitting one. The mean degree of disability was 3.6 in Kurtzke's scale. The evolutive form and the duration of the disease were identified as predictive of disability. 43.5% of benign forms and 13.1% of late onset forms were identified.