Multiple Sclerosis (MS)
Multiple Sclerosis (MS) affects over 16,000 Australians, ¾ of them women of working age. Onset is at 20 to 40 years, and its lifelong effects cost Australia about $2 billion p.a. MS causes more disability and loss of life than rheumatic heart disease, chronic back pain or mental retardation. Vitamin D plays a role. It is produced by sunlight. Low levels seem to increase MS prevalence and therefore communities at higher latitudes, with longer winters, have higher prevalence of MS, even in Australia. Prevalence in Tasmania is about 68/100k persons, Newcastle 33, and Queensland 11.
MS reduces the speed at which nerve-fibres conduct their signals within the brain and large nerves. The distribution of damage across the central nervous system due to MS is patchy and occurs rather randomly over time. About 85% of patients show a pattern of acute symptomatic episodes followed by longer periods of remission when their symptoms subside. The symptoms depend on which part of the nervous system was acutely affected by localised inflammation. More than one area can be affected. Remission is not a cure and damage accumulates, raising the chances of ongoing disability. Vision is affected in about 20% of attacks, motor skills in about 25%. The other 15% of subjects show gradual decline across various brain systems without acute inflammatory episodes.
Magnetic Resonance scanning has been very helpful in the diagnosis and management of MS but its results are more related to inflammation than to accumulating degeneration. For this reason, Vison ACTion and Partners are developing diagnostic methods that are more related to degeneration in order to help guide treatment decisions. Many more treatments have come onto the market in recent years, but the questions of which drug is best for a given patient, and how to decide when to switch treatments, are problematic. Having biomarkers that are better related to progression of disability would help.
If MS affects many part of the central nervous system, why are we interested in vision? The optic nerves, connecting the eyes to the brain, have about as many nerve-fibres as the spine so are affected about as often. As mentioned above, the optic nerves branch out into the brain via the optic radiations. Compared to other comparable nerve-fibre bundles in the brain the radiations are highly susceptible to damage by MS. Thus, measuring visual function assesses a sensitive target. In fact, our new methods are as good at discriminating eyes of patients that have and have not experienced acute inflammation, and those measures are well correlated with disability.