Benign multiple sclerosis? Clinical course, long term follow up, and assessment of prognostic factors.

OBJECTIVE To establish the characteristics of patients following a benign course of multiple sclerosis and evaluate the importance of potential prognostic factors. Also, an assessment of the value of the Kurtzke EDSS as a prognostic indicator has been undertaken in patients previously determined to have benign multiple sclerosis, after 10 years of follow up. METHODS A prevalence study in the Coleraine, Ballymena, Ballymoney, and Moyle districts of Northern Ireland used the Kurtzke expanded disability scale score (EDSS) in 259 patients with multiple sclerosis. Of these, 181 had had multiple sclerosis for>/=10 years, 36 having benign disease (EDSS/=10 years after onset. Clinical and demographic details of the various patient groups, including the minimal record of disability, were compared. The 1987 study in Northern Ireland identified 33 patients with benign multiple sclerosis. Twenty eight were available for follow up in 1996 along with 42 contemporary non-benign patients. RESULTS Patients with benign multiple sclerosis were predominantly women (ratio 4.1:1 v 2.1:1) and younger at onset (25.8 v 31.2 years). Commonest symptoms at onset were sensory and optic neuritis (33.3% each). Patients with late onset (older than 40 years) were less likely to have a benign course, more likely to have a progressive course from onset, significantly more likely to have motor disturbance at presentation, and had a lesser female predominance. Optic neuritis was significantly more common in those with a younger age at onset. In the follow up study, patients with benign multiple sclerosis continued to have a more favourable course than non-benign counterparts but progression of disability and to the secondary progressive phase remained significant. CONCLUSIONS The association of female sex, early onset, and presentation with optic neuritis and sensory symptoms with a favourable course is confirmed. However, although the EDSS does provide a useful indicator of prognosis, the label "benign multiple sclerosis" is often temporary as apparently benign disease often becomes disabling.