EDMUS

The Lyon Multiple Sclerosis Cohort

The Lyon Multiple Sclerosis Cohort gathers the files of all patients with Multiple Sclerosis (MS) examined at least once in the neurology department in Lyon since 1957 (today the Service de Neurologie A in Hôpital Neurologique Pierre Wertheimer). It was constituted in 1976, with the creation of a standardized form and the development of a corresponding software program, prefiguring the development of the EDMUS software, released in 1992. The Hospices Civils de Lyon issued on August 7, 1992 a regulation allowing the use of the EDMUS software in the hospital for "the computerized collection of nominative information for the management of patients with Multiple Sclerosis".

The cohort continues to grow in a prospective manner, through visits and hospitalizations, with the update of existing patient files and the addition of new files. As of today, it contains more than 5,500 patients. It represents the most important MS cohort in the world.

The "historical" cohort of 1844 patients

Part of the Lyon cohort had been gathered before 1997, i.e. before the first disease-modifying treatments received marketing autorisation in France. These files make up the "historical" Lyon MS cohort, containing 1,844 patients. This cohort represents a unique epidemiological material, not reproducible in the future precisely because of the generalisation of disease-modifying treatments likely to affect the course of the disease. One may consider that this cohort is representative of the disease natural history.

The study of this cohort has brought several important advances in our knowledge of the natural history of untreated MS:

• The description of the evolution and overall prognosis of the disease (Confavreux & Compston, 2006); this description had been initiated as early as 1980 in the neurology department of Lyon with, for the first time, the use of Kaplan-Meier survival curves (Confavreux et al, 1980).
• The accumulation of irreversible disability is but little influenced by acute relapses. It depends, for the most part, on the phenomenon of clinical "progression" of the disease. This is the concept of "dissociation" between relapses and progression in the mechanisms leading to the accumulation of disability (Confavreux et al, 2000).
• Identifiable clinical parameters at disease onset have a predictive value for the time required to reach the first levels of disability. Beyond this threshold, they have no predictive value any more for the speed at which subsequent disability accumulates. This is the concept of "amnesia" in the accumulation of disability (Confavreux et al, 2003).
• Times to reach the different levels of irreversible disability are essentially dependent on the age of the patient (Confavreux & Vukusic, 2006a).
• In spite of the high variability of its clinical forms and the variable rates of its evolution, it is possible to argue, from a clinical and statistical position, for a unifying concept of the disease. The clinical phenotype and accumulation of disability are age-dependent (Confavreux & Vukusic, 2006b).

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