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Cognitive Dysfunction

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Cognition refers to a range of high-level brain functions, including the ability to learn and remember information: organize, plan, and problem-solve; focus, maintain, and shift attention as necessary; understand and use language; accurately perceive the environment, and perform calculations. Cognitive changes are common in people with MS—approximately 50% of people with MS will develop problems with cognition.

  • A person may experience difficulties in only one or two areas of cognitive functioning or in several.
  • Only 5-10% of persons with MS develop problems severe enough to interfere significantly with everyday activities. In very rare instances cognitive dysfunction may become so severe that the person can no longer be cared for at home.

Cognitive Functions Affected in MS

In MS, certain functions are more likely to be affected than others:

  • Memory (acquiring, retaining, and retrieving new information)
  • Attention and concentration (particularly divided attention)
  • Information processing (dealing with information gathered by the five senses)
  • Executive functions (planning and prioritizing)
  • Visuospatial functions (visual perception and constructional abilities)
  • Verbal fluency (word-finding)

Certain functions are likely to remain intact:

  • General intellect
  • Long-term (remote) memory
  • Conversational skill
  • Reading comprehension

The Relationship between Cognitive Dysfunction and other Disease Factors

Cognitive problems are only weakly related to other disease characteristics—a person with almost no physical limitations can have significant cognitive impairment, while a person who is quite disabled physically can be unaffected cognitively.

  • Changes can occur at any time—even as a first symptom of MS—but are more common later in the disease.
  • Cognitive function correlates with number of lesions and lesion area on MRI, as well as brain atrophy.
  • Cognitive dysfunction can occur with any disease course, but is slightly more likely in progressive MS.
  • Being in an exacerbation is a risk factor for cognitive dysfunction.
  • Cognitive changes generally progress slowly but are unlikely to improve dramatically once they have begun.

The Importance of Early Diagnosis and Treatment

Early recognition, assessment, and treatment are important because these changes—along with fatigue—can significantly affect a person’s quality of life and are the primary cause of early departure from the workforce. The first signs of cognitive dysfunction may be subtle—noticed first by the person with MS or by a family member or colleague.

  • Difficulty finding the right words
  • Trouble remembering what to do on the job or during daily routines at home
  • Difficulty making decisions or showing poor judgment
  • Difficulty keeping up with tasks or conversations

People with MS and their families should talk to the doctor if they are concerned about cognitive dysfunction. A careful evaluation is necessary to determine the cause(s) of mental changes since cognitive function can also be affected by aging or medications, as well as depression, anxiety, stress, and fatigue.

  • A specially trained health professional (neuropsychologist, speech/ language pathologist, or occupational therapist) administers a battery of tests to evaluate cognitive dysfunction.
  • Based on the test findings—including the person's cognitive deficits and strengths—the health professional can provide cognitive rehabilitation, including:
    • Computer-mediated memory exercises
    • Training in the use of compensatory strategies such as notebooks, computers, and filing systems to compensate for memory problems and other changes.

Research on MS and Cognition

Studies are ongoing to identify ways to stabilize or improve cognitive dysfunction. Since the disease-modifying drugs have all been shown to reduce the accumulation of new demyelinating lesions, it is likely they help to stabilize cognitive changes. However, more studies are needed to determine their effectiveness in this area.

Symptomatic treatments that may temporarily improve cognitive functioning without altering its long-term course have been studied. To date the most successful has been donepezil hydrochloride, showing modest improvement in verbal memory.

Studies funded by the National MS Society are investigating the natural history of cognitive changes, along with better ways of diagnosing and treating cognitive problems in MS. It is hoped that in the future, people with MS will have access to a combination of disease-modifying therapies, symptomatic treatments, and cognitive rehabilitation that will modify the course and impact of the cognitive changes in MS.