Background: The multiple sclerosis severity scale (MSSS) adds the element of disease duration to the expanded disease status score (EDSS) and is designed to provide a measure of disease severity. We have used this tool to address two questions: Can it be used to predict the accrual of disability over time in individual patients? Do the currently available therapies have an impact upon disease severity over time?
Methods: All patients who were followed and treated by a single neurologist in an MS center in the USA over a two year period were evaluated. The MSSS was retrospectively tabulated in 195 MS patients and the course and severity of the disease was analyzed in a sample of 10 randomly selected patients. 177/195 (94%) of patients received disease-modifying therapies for at least a year during the period that was evaluated.
Results: The mean duration of symptoms in our patients was 9.7 years (range 0.3-26) with an EDSS mean score of 3.5 (range 0-9.5). The average MSSS rating for the entire cohort of 195 patients was 48.7, similar to that observed in the European cohort. In 9/10 patients, randomly selected and representative of the entire group, the MSSS assessments were consistent over time and irrespective of therapy with a range over 5-12 years of disease duration averaging only 11.3 points (range 3.7-18.8).
Conclusions: The MSSS may allow the prediction of disease severity over time, and is consistent with the lack of a major impact of disease-modifying drugs upon disease severity as measured by the MSSS. These results need to be verified in a larger cohort of patients.