Of all the types of functional difficulties that a patient with multiple sclerosis (MS) can experience, cognitive change remains the area that is hardest to delineate. MS patients may experience changes in memory, attention, reasoning and executive function that can be subtle and therefore hard to detect clinically, but significant enough to compromise their daily function. Many are forced to change occupation and cut down workloads and personal responsibilities due to these changes. It may be tempting to put a lot of these cognitive changes down to fatigue and medication side effects, but it has long been suggested that there are discrete changes in cognition in MS that occur without any contribution from other factors. The difficulty has also been finding a way to measure this. In some patients, cognitive difficulties fluctuate and yet without knowing how to evaluate these changes we are not able to view them in the same way that we would view a sudden change in visual function or in walking speed. Therefore, cognitive deterioration has never sat well in the minds of clinicians as a legitimate form of MS relapse and yet there is no scientific basis to exclude it from consideration.
In the current issue of JNNP, Pardini and colleagues from Genoa http://jnnp.bmj.com/content/85/9/1035.abstract provide some very interesting data that may be viewed as a platform to further studies investigating the possibility of cognitive changes as a bona fide form of MS relapse. In their study, the authors undertook serial studies in 99 patients with relapsing-remitting MS. The authors used a validated cognitive test, the symbol digits modality test as a measure of cognitive change. They found that there were isolated cognitive relapses in 17 patients, i.e. a significant proportion of the group.
The study is interesting and important as it provides clear insights into the cognitive changes that may occur in otherwise ‘stable’ MS patient. The authors also show that these changes occurred without any other alteration in mood or fatigue, suggesting that isolated cognitive relapses are a real phenomenon and a potential contributor to cognitive decline in MS.