Scales for rating impairment in multiple sclerosis: a critique.

We reviewed scales proposed over the past 35 years for the rating of neurologic impairment in MS. We focused on the Expanded Disability Status Scale (EDSS) which has been recommended as the most useful scale for rating impairment by the International Federation of Multiple Sclerosis Societies in its Minimal Record of Disability for Multiple Sclerosis. We consider that the EDSS has important flaws that seriously limit its usefulness. In light of the widely accepted three-tier classification of dysfunction developed by the World Health Organization, the title is inappropriate. More substantial problems include inadequate precision in defining the degree of impairment in some functional categories of the scale, and the use of a mixture of neurologic signs elicited on examination and subjective information obtained from the patient in defining the overall scale. We suggest guidelines for developing a "Neurologic Impairment Scale" to rate impairment in MS.