Progressive cognitive decline in patients with multiple sclerosis (MS) may not be as inevitable as previously thought, a study suggests.
The study, “A longitudinal study of cognitive function in multiple sclerosis: is decline inevitable?,” was published in the Journal of Neurology.
Statistics indicate that some kind of cognitive impairment affects up to two-thirds of all MS patients, including memory deficits or problems with processing information. Once a patient starts showing signs of cognitive decline, it is often assumed symptoms will inevitably worsen as MS progresses.
However, findings from a new study carried out by researchers in Greece are challenging this scenario.
Investigators reviewed data from 59 patients — 14 with clinically isolated syndrome and 45 with relapsing-remitting MS — evaluating their cognitive decline over a decade. Cognitive impairment was assessed using the Brief Repeatable Battery of Neuropsychological Tests, a standard tool for this purpose, at baseline (study’s start; 2004–08) and again approximately 10 years later (2015–17).
Analyses revealed roughly a 10% increase in measures of overall cognitive impairment over the course of 10 years in the MS group analyzed — from 42% at baseline to 52.5% at follow-up.
A more detailed analysis of five separate cognitive domains assessed in the test (verbal memory, visual/spatial memory, working memory, processing speed, and cognitive flexibility) suggested this rise was mainly driven by a decline in verbal memory.
Cognitive impairment at 10 years was not associated with the occurrence or number of relapses in the intervening time, nor with disability (as measured by the Expanded Disability Status Scale) at any time point.
But investigators noted these overall results masked interesting patterns seen when data were assessed on a case-by-case basis.
“[L]ooking at individual patient performance at baseline and follow-up in all five cognitive domains investigated, one can discern several cases who have failed in fewer domains at follow-up compared to baseline, or who have failed at different domains at follow-up compared to baseline,” the researchers wrote.
In general, patients with normal memory-related scores at the first assessment were more likely to be impaired in these domains 10 years later.
Those with normal information processing speed scores, however, rarely showed a decline a decade later.
Some with baseline impairments in working memory and/or verbal fluency also experienced significant improvements in cognitive abilities 10 years on, often to the point of no longer being considered impaired.
“Cognitive impairment at baseline does not by default lead to progressive decline. Although the overall proportion of cases with cognitive impairment increases over time, there are several patients who improve over the years in specific cognitive domains, while they may or may not decline in other domains,” the researchers wrote.
“This ‘bouncing-back’ of cognitive function in impaired-at-baseline patients is an intriguing phenomenon that may reflect the [damage] compensation capabilities of the brain in ΜS patients,” they added.
The team also noted that other factors may be involved, like anxiety, which has been shown to negatively affect cognitive function in those with MS. Further research is needed to validate these results and clarify the underlying mechanisms, the researchers wrote.
They also emphasized that future studies should include a larger and more representative MS patient group, and suggested that shorter and multiple points for assessing changes in cognition over time — like at two and five years, as well as 10 — would enable a more detailed assessment of decline.
Nonetheless, “this study suggests a more fluid picture for the evolution of cognitive function in a subgroup of MS patients, and contradicts the concept of an inevitable, progressively evolving ‘dementia,'” the team concluded.