Posted by: Thixia | April 26, 2008

Nature of Cognitive Dysfunction in MS 1 of 6

I.       Introduction

 

Some of the most common and most disabling symptoms of MS are “the invisible symptoms of MS,” which include the related problems of depression, fatigue, and cognition. 

 

Cognition is a general term that refers to the mental activities associated with thinking, learning, and memory. Cognitive dysfunction, also a general term, refers to problems with cognition.

 

There is both good news and bad news to report about cognitive problems among people with MS.  The bad news is that such problems are relatively common, usually estimated to occur in about 45-65% of those with MS. And, not surprisingly, the impact of cognitive problems can be substantial; those with more severe cognitive problems are less likely to work, tend to experience less social involvement, and have more difficulty with everyday tasks.  In addition, cognitive problems may make driving dangerous for some.

 

The good news is that many people with MS will not have any cognitive decline, and many who do experience only mild problems.  In the majority of cases, cognitive decline in MS is not severe.  Sometimes, the problems that develop may be focal, affecting only particular aspects of cognition. There is also preliminary information suggesting that cognitive decline may be slowed by injectable medications.  Finally, although there are no treatments that are established as effective, there are suggestions in the literature that some interventions may be helpful. 

 

 

 

II.    Nature of Cognitive Dysfunction in MS

 

The most salient feature of cognitive dysfunction among people with MS may be that it does not conform strictly to any particular pattern.  In other words, cognitive dysfunction in people with MS varies from one person to another.   This, in part, is because cognitive dysfunction among people with MS, as with people who do not have MS, may be the result of a complex combination of medical and psychological factors, including, depression, other mood problems, medications, sleep problems and other medical conditions.  Variability of cognitive dysfunction is also probably a consequence of the variability of the disease itself, relating to the differences in the number of MS lesions, the location of the lesions in the brain, the severity of those lesions, and even the amount of microscopic damage that occurs in areas of the brain that look normal with conventional MRI imaging.

 

Beyond its variability, there are competing ideas about the nature of cognitive problems in MS.  Some have assumed that cognitive dysfunction in MS is global, affecting all aspects of cognition.  This global effect may be related to a general slowing of information processing.   Another view is that MS may cause focal rather than global impairments.  As noted by one researcher: 

 

MS does not resemble a global, homogeneous decline in cognitive abilities…. Rather a “typical” pattern of deficits is observed on measures of recent memory and conceptual reasoning, with verbal intellectual ability and primary language skills seemingly unaffected by the disease….

 

A middle ground may also be possible, namely that while cognitive decline may be global, possibly affecting all aspects of cognitive function, some aspects of cognition tend to be affected more frequently than others.  More clarity may emerge as the issue is studied further. 

 

To understand the particular patterns of cognitive dysfunction that have been reported among people with MS, it is necessary to consider specific aspects of cognition.  These include such areas as memory, language, and problem solving. 

 

Defined as the number of people scoring below the fifth percentile, the most frequently occurring cognitive problems among people with MS include memory problems, a slowing of information processing speed, difficulty with problem solving, and difficulty with visual-spatial skills.  In the discussion that follows, the numbers in parentheses refer to the percentages of people with MS who may experience the listed problem with cognition.

 

Memory (22-31%):  This is the cognitive complaint most frequently described by people with MS.  To understand the nature of memory problems in MS, it is helpful to talk about specific kinds of memory.  Memory may be either explicit or implicit.  Explicit memory is the ability consciously to recall information, such as remembering the name of a celebrity or being able to recall factual information during an examination in school.  Implicit memory, on the other hand, is the ability to depend on prior learning without conscious effort.   An example of this is the way someone might learn directions by driving a car.

 

 

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Responses

  1. What is the difference with memory loss caused by MS or by aging? How can these two sources of memory loss be determ,ined and what is the solution for each? Is there a way to reduce memory loss in a sixty year old person with a mild form of MS?

    Thank you


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