Benign multiple sclerosis: a need for a consensus.

OBJECTIVES: To investigate the impact of different definitions on the frequency of benign multiple sclerosis (MS) in patients with a long follow-up, and to study the presence of non-motor symptoms and employment across the definitions.
MATERIALS AND METHODS: All patients alive (n = 188) with disease onset during 1976-1986 in Hordaland County, Norway, were clinically examined including the Expanded Disability Status Scale (EDSS) in 2003. Non-motor symptoms which included depression, cognitive impairment, fatigue and pain, and employment status were also registered. Three definitions of benign MS were used based on the following EDSS cut-off values: 2.0, 3.0 and 4.0. Two additional definitions were added using an EDSS <or=4.0 and incorporating either full-time or full- and part-time employment status.
RESULTS: The frequency of benign MS increased from 14.5% for EDSS <or=2.0 to 40.8% for EDSS <or=4.0, but was only 12.3% for the definition based on full-time employment. Patients with an EDSS <or=2.0 had markedly less non-motor symptoms and lower unemployment rates than the other groups.
CONCLUSIONS: An EDSS score <or=2.0 with at least 10 years of disease duration seems to be the most appropriate criterion in identifying patients with benign MS.