Just under half of people with MS say that they experience significant cognitive difficulties. When their cognition is formally assessed on psychometric tests in group studies, approximately half will have some demonstrable inefficiency. When the people with MS are recruited from the community, slightly less than half will show this effect on tests. When the people with MS are recruited from a university clinic, slightly more than half will have a demonstrable inefficiency. Test scores do not relate to how people manage in everyday life in a simple way. This is partly because of external factors influencing test performance (see contributory factors).
The types of tasks that are most likely to be affected in MS are those requiring complex attention (for example, difficult arithmetic problems done without paper and pencil) and memory for information that has just been heard or seen (e.g. remembering a list of words). Increasingly, research is pointing towards an underlying slowing in mental processing that explains all other cognitive difficulties.
Change in cognitive abilities over time is often slow or non-existent. In very long studies, which collect information over 10 years or more, it seems that there is a gradual accumulation of cognitive difficulties over time. Such studies indicate that those individuals most at risk of acquiring cognitive difficulties are those who present with them in the earliest stages of the study.
Studies have pointed towards different cognitive profiles for the different MS subtypes (relapsing/remitting, primary progressive, secondary progressive and benign). Cognitive deficits tend to be more widespread and more severe.
Amato MP, Zipoli V, Portaccio E. Multiple sclerosis-related cognitive changes: a review of cross-sectional and longitudinal studies. J Neurol Sci 2006; 245(1):41-6.
Benedict RH, Zivadinov R. Risk factors for and management of cognitive dysfunction in multiple sclerosis. Nat Rev Neurol. 2011 May 10;7(6):332-42.
Chiaravalloti ND, DeLuca J. Cognitive impairment in multiple sclerosis. Lancet Neurol 2008; 7(12):1139-51.
Langdon DW. Cognition in multiple sclerosis. Curr Opin Neurol. 2011 Jun;24(3):244-9.
Protecting cognitive function
There is now good scientific evidence that positive lifestyle choices will protect function in the context of MS, including maintaining cognition: less (or better no) smoking, less (or better no) alcohol, regular exercise, maintaining a healthy weight, being prescribed optimum disease modifying medication and taking it by the numbers, and being prescribed optimum treatment for all other diseases (especially cardiovascular and diabetes). Particularly for cognition, regular challenging mental activity helps maintain clear and fast thinking.
Rehabilitation to improve cognitive difficulties
Cognitive rehabilitation studies tend to take one of four approaches:
- cognitive retraining through drills and exercises (often computerised);
- neuropsychology-model based interventions, which rely on theories of how the brain stores and processes information to develop and teach strategies which the person with MS can apply to different situations;
- eclectic, drawing on neuropsychology, cognitive psychology and behavioural psychology;
- holistic, addressing motivation, emotion and other psychological needs, in addition to specific cognitive skill training.
Cognitive retraining provides the most convincing evidence, but that doesn’t necessarily mean that cognitive retraining gives the best improvements in people’s lives.
Cognitive training fits best into the model of a randomised controlled trial. When a drug treatment is evaluated, a randomised controlled trial is carried out. Participants are randomly allocated to receive either treatment or placebo. It is relatively hard to tell a placebo tablet from a real tablet, when they have been designed to look the same. But it is much harder to devise a placebo rehabilitation programme. This means that the therapists delivering the programme and usually the participants as well, know who is receiving the “real” treatment. This can compromise the objectivity of the evaluation of the treatment.
Most rehabilitation studies rely on using neuropsychology tests of different mental skills. The scores before and after training are used to determine if positive change has occurred, compared to the placebo intervention. Not all studies ask the participants if they found the programme useful. Very few attempt to find out if managing in daily life improved.
Chiaravalloti ND, Moore NB, Nikelshpur OM, DeLuca J. An RCT to treat learning impairment in multiple sclerosis: The MEMREHAB trial. Neurology. 2013 Dec 10;81(24):2066-72.
Pedullà L, Brichetto G, Tacchino A, Vassallo C, Zaratin P, Battaglia MA, Bonzano L, Bove M. Adaptive vs. non-adaptive cognitive training by means of a personalized App: a randomized trial in people with multiple sclerosis. J Neuroeng Rehabil. 2016 Oct 4;13(1):88.
Pérez-Martín MY, González-Platas M, Eguía-Del Río P, Croissier-Elías C, Jiménez Sosa A. Efficacy of a short cognitive training program in patients with multiple sclerosis. Neuropsychiatr Dis Treat. 2017 Feb 3;13:245-252.
Rilo O, Peña J, Ojeda N, Rodríguez-Antigüedad A, Mendibe-Bilbao M, Gómez-Gastiasoro A, DeLuca J, Chiaravalloti N, Ibarretxe-Bilbao N. Integrative group-based cognitive rehabilitation efficacy in multiple sclerosis: a randomized clinical trial. Disabil Rehabil. 2016 Dec 7:1-9.