Multiple sclerosis is an auto-inflammatory disease leading to loss of myelin, an insulating sheath surrounding the nerves which improves signal transmission speed, in the central nervous system. This process, called demyelination, results in impaired neuronal function. The consequent symptoms depend on the site of the destruction, and may include a wide range of autonomic, visual, motor and/or sensory symptom. Visual impairment, walking difficulties and sensory dysfunction are the most common initial symptoms. With time, the disease may cause significant disability and also results in a shorter life expectancy.
Most often, MS initially has a relapse-remitting pattern, characterized by attacks of worsening followed by periods of improvement. Over time, the disease may take a more progressive character with gradually decreasing neuronal function without periods of improvement, called secondary progressive MS. In approximately 10% of cases, the disease takes a progressive character already from start, and is then denoted as primary progressive MS. Taken together, it is estimated that approximately 50% of all MS patients are in a progressive phase of disease.
MS typically presents at between 20 to 40 years of age and is more common in women than in men. The number of affected individuals varies widely across geographies and is most common in the Northern hemisphere. In Europe, it is estimated that on average 80 per 100 000 inhabitants suffer from MS, equal to approximately 400 000 individuals within the EU. The underlying causes or triggers are not known. The disease does not follow typical inheritance patterns and is thus not considered inherited, but the difference in geographical incidence may suggest a role for environmental factors, possibly coupled with genetic susceptibility.
While there are several therapies approved for and effective in the management of relapse-remitting state of MS, there are still only few treatment options available for the treatment of progressive MS.