Posted by: Thixia | April 28, 2008

Nature of Cognitive Dysfunction in MS 3 of 6

IV.  Prevention


A.     MS-specific strategies


Preventing cognitive decline in MS, obviously, is an important goal. Whether current FDA-approved MS therapies can prevent cognitive dysfunction has received only limited study.    There have been only two large, well-designed clinical trials to investigate the effect of treatment with injectable medications on cognitive function over time


A beneficial effect on development of cognitive dysfunction in MS has been reported for Avonex (interferon beta-1a).   In this complicated trial, three different groups of tests, or batteries, were administered to two groups of people: those receiving Avonex and those receiving placebo.   Each of the three batteries was designed to assess different aspects of cognition over a two year period:


Test A:      memory and information processing speed

Test B:      visual-spatial abilities and problem solving

Test C:      attention and verbal abilities


Over the course of two years, the group receiving Avonex experienced less cognitive decline than the group receiving placebo on Test A.  No such differences were seen with Test B or Test C.   Thus, a beneficial treatment effect was seen in the areas that seem most often to be affected by MS.


Whether Copaxone (glatiramer acetate) might prevent or slow cognitive dysfunction has also been investigated in a two-year trial.  No beneficial effect was observed with Copaxone therapy.  However, during the course of the trial the group receiving placebo did not experience any decline.  This unexpectedly good performance of the placebo group may have masked a beneficial treatment effect due to Copaxone.   


There have been three preliminary studies addressing whether cognitive dysfunction may be prevented with Betaseron (interferon beta-1b) .  One study found that Betaseron prevented decline on certain tests of memory, but not in other tested areas, including attention and information processing.  This study involved only 30 patients.   The two other studies are of lower quality.   A group of 73 people who had been taking Betaseron for at least six months was compared with a group of 94 people who was waiting to begin therapy with Betaseron on measures of memory.  No difference between the two groups was observed.  Finally, a group of 23 people receiving Betaseron was compared to a group who was not receiving treatment.  The group receiving Betaseron scored better on certain tests of memory, attention and processing speed, and visual spatial recall; on other tests there was no difference between the two groups.


It seems reasonable to assume that any treatment that produces improved findings on MRI as well as on clinical outcomes such as relapse rate or physical disability progression, would also have a favourable effect on cognitive decline.  However, there is only limited evidence to support that view.  Avonex is the only FDA-approved therapy that has been shown to produce a beneficial effect on measures of cognitive decline in a large, well-designed trial. 


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