One related area regarding MS pathogenesis
is that of the outward manifestation of the
disease. Most cases of MS start with a relapsing-remitting
(RR) character which refers to short periods
when new symptoms appear or old ones increase
(attack or exacerbation) and long intervals
when symptoms improve somewhat or stabilize
(remissions). On average it would appear
a typical case involves about one attack
a year (Sibley, 1992). Notably it has been
found through MRI studies that lesion forming
activity occurs even during remissions (Lai
et al., 1996). Thus in many cases it would
appear as if disease activity is essentially
continuous with a waxing and waning character.
In many instances RRMS evolves into secondary
progressive (or chronic progressive) MS where
there are no clear relapses and remissions,
only gradual deterioration.
In some cases, MS does not present in a relapsing-
remitting manner but rather gradual deterioration
begins at onset. This type of MS is known
as primary progressive MS.
If untreated, RRMS can have a highly variable
course in terms of disabilities although
an average rate of decline of one EDDS (a
scale for assessing disability state) level
every six years has been documented (Swank
and Dugan, 1987; Sibley, 1992).
Any proposed cause of MS should be
able to
explain the various types of MS and
the observed
average decline rate.
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