The Expanded Scale of Disability Status (EDSS), developed by the neurologist John F. Kurtzke and published in the journal "Neurology" in 1983, is the most widespread scale in the assessment of patients suffering from Multiple Sclerosis. Patients are evaluated based on the neurological examination and clinical history for each functional scale (FS) and then a global score is obtained taking into account the ability to walk. You can consult the original article by Dr. Kurtzke in PubMed: https://www.ncbi.nlm.nih.gov/pubmed/6685237