On the origin of EDSS

Abstract

The origin of EDSS, the Expanded Disability Status Scale for multiple sclerosis, was some 30 years before its only publication in 1983 when we were trying to assess a potential treatment and found no published methods. Findings from the complete neurologic examinations in over 200 patients were consolidated into mutually exclusive but all-inclusive neurophysiologic entities called Functional Systems (FS), and these provided the basis for an 11 step 0-10 rank order scale, the Disability Status Scale (DSS). This was used successfully, as well as in the first two Class I treatment trials performed, with the second one also incorporating the 8 FS. Both measures were part of an assessment of a natural history series derived from men hospitalized for MS in the US Army in World War II and followed for some 20 years. Describing each of the 8 FS as affected (1) or normal (0) defined 256 possible patterns of involvement for all patients. Half the patients at diagnosis had one of the 14 most common patterns. Each FS worsened in frequency and severity of involvement in correlation with the DSS, which overall showed a unimodal distribution, until in another series of patients 16 years post onset bimodality first appeared. Observations that the 11 step DSS might have too few steps for treatment trials led to the EDSS of 20 steps with each grade between 1 and 9 divided into two. The system of EDSS+FS to summarize all the CNS involvement as defined by objective findings on neurologic examination thereafter remained unchanged to the present. I just learned that the unpublished system copyrighted in Switzerland as "neurostatus" has been called and referenced as my EDSS. It is not.

Keywords: DSS; Disability measurement; EDSS; Functional systems (FS); MS; Treatment trials.