Cognitive Function in MS
Anthony Feinstein MPhil, PhD, FRCP
Professor, Department of Psychiatry
University of Toronto and Sunnybrook Health
Multiple Sclerosis (MS) is the most common non-traumatic cause of neurological disability in young and middle-age adults. MS affects balance, vision, strength and coordination. These symptoms are often quite visible. However, some symptoms are invisible and may be even more disabling. Examples include pain, fatigue, depression and cognitive dysfunction.
Prevalence and nature of symptomsCognition refers to how we think, identify knowledge and understand it. Cognitive difficulties affect between 40 and 70% of people with MS. Individuals with progressive MS are more likely to have cognitive problems than individuals with relapsing-remitting MS. Problems with thinking and memory can start early in the disease. These problems may worsen over time interfering with day-to-day functioning.
The typical cognitive abnormalities that occur in people with MS are a decrease in processing speed, impairments in working memory and learning and deficits in executive functions. Processing speed refers to the time it takes to do a mental task. Executive function refers to a person’s ability to plan and execute solutions to problems while remaining flexible in terms of the decision-making processes. Of all these cognitive challenges, it is the slowing of information processing speed that is considered the cardinal cognitive difficulty linked to MS.
Processing speed can be assessed in many ways. Researchers who study cognitive function in MS agree that the Symbol Digit
“Of all these cognitive challenges, it is the slowing of information processing speed that is considered the cardinal cognitive difficulty linked to MS.”
Modalities Test (SDMT) is the best method. The SDMT is a sensitive way of detecting problems. The test is short, can be done easily in individuals who are experiencing fatigue and it is not anxiety-provoking. Given the usefulness of this particular test, several versions of the original test are being used in MS research.
The original SDMT was conducted in-person and administered by a tester. Newer versions of the SDMT can be self-administered with an iPad or through voice recognition on a computer. Studies show that these self-administered versions of the SDMT work as well as the original tester-driven method for assessing information processing speed in people with MS. Indeed, some data suggest that people with MS prefer the computerized administration.
“One of the challenges of cognitive testing is to ensure that the data collected has real world meaning.”
One of the challenges of cognitive testing is to ensure that the data collected have real world meaning. Until now, neuropsychological (cognitive) testing has taken place in an office with a sign outside the door asking passersby to be quiet. As such, an environment free of distraction is created for the cognitive assessment. There is now a movement underway to change this by making the testing environment more reflective of the situations confronted by people with MS in the real world. Introducing cognitive testing into a person’s home is one way to do this. It is one of the reasons why voice recognition, computer administered tests like the SDMT have been developed.
Managing cognitive symptoms
Assessing cognition is the first step in determining whether an individual with MS has cognitive deficits. If the testing reveals the presence of deficits then attention turns to treatment. Treatment can take various forms. The most widely available approach is to introduce cognitive compensatory strategies. This refers to helping people with MS learn certain techniques that allow them to work around their cognitive problems to reduce their impact. For example, if a person has memory difficulties then one of the compensatory strategies is to make lists or to use electronic reminders on a smart phone or tablet.
In addition to cognitive compensatory strategies there is now an emerging literature that speaks to the potential benefits of cognitive rehabilitation. Currently, this particular intervention is only available within clinics and rehabilitation centers. Here the aim is to see whether one can bring about an improvement in a person’s cognitive difficulties. Much research still needs to be done to determine exactly how such an intervention works and the degree to which it can bring about clinically meaningful change.
It has taken many years of research and advocacy for the medical profession to understand the importance of cognitive difficulties in a disease like MS. Individuals with cognitive impairment have greater difficulty finding work, sustaining work, managing relationships, pursuing leisure activities and enjoying a good quality of life. Therefore it is imperative that researchers and clinicians work together to make testing for cognitive impairment readily accessible. Technology may help to achieve this goal, and could support evaluation of treatments in the future.
“…there is now an emerging literature that speaks to the potential benefits of cognitive rehabilitation.”