Disability rating scales in multiple sclerosis.

The International Federation of Multiple Sclerosis Societies has been attempting to define a Minimal Data Set for multiple sclerosis following the tripartite scheme of the World Health Organization, with one rating scheme for neurologic signs, one for physical disabilities, and one for the societal impact of the disease. Current recommendations are the Disability Status Scale or the Expanded DSS plus Functional Systems for the first, Incapacity Status Scale of 16 items for the second, and Environmental Status Scale of 7 items for the third. All are graded in an ordinal (rank) scale from 0 (normal) with larger numbers for greater involvement. ISS scores range from 0-4 and ESS from 0-5 for each item. The only part of this scheme useful for measurement in clinical trials is the (E)DSS + FS. The DSS ranges from 0-10; EDSS subdivides each DSS grade 1-9 into two. FS are pyramidal, cerebellar, brain stem, sensory, bowel and bladder, visual, cerebral, or other; all save the last are graded 0-5 or 0-6. The DSS correlates well with both frequency and severity of involvement in all FS, which in turn represent a coded standard neurologic examination.