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.
Except perhaps among people with primary progressive MS, implicit memory is not usually affected. On the other hand, people with MS may experience problems with explicit memory. Explicit memory is also sometimes classified as being immediate (lasting seconds), recent (minutes, hours, or days) or remote (years in the past). All of these aspects of memory may be affected in MS, but immediate memory may be less affected than other aspects of memory. In practice, people with MS may find it difficult to recall and describe details of a book or a movie.
In a review of multiple studies, a strong relationship between memory problems and both disease duration and neurological disability has been observed; in other words, those with more physical limitations tend to have more difficulty with memory. However, such problems may also occur relatively early in the disease and among people with few physical limitations.
Attention and Information-Processing Speed (22-25%): Because the processing of information quickly also requires attention, these are often discussed together. Some people with MS may have trouble with complex tasks, such as adding a series of numbers in their head. Some measures of information-processing speed seem to relate to the amount of damage seen on MRIs of the brain. People with deficits in this area may have trouble keeping up with details of conversation and may not be ready to move on in a conversation when others try. Visuoaspatial difficulties may interfere with driving ability and driving safety.
Visual-spatial skills (12-19%): Visual spatial skills include judging the relationship of lines and angles and perceiving of faces. People with problems in this area might have trouble recognizing faces or driving.
Conceptual reasoning (13-19%): Conceptual reasoning includes the ability to solve problems and demonstrate flexibility in reasoning. In particular, people with MS may be prone to perseverative errors, which means that they may persist (or persevere) with an approach to a problem despite evidence that the approach is not working. While some evidence indicates that this problem occurs frequently, there is other evidence to show that the magnitude of this particular aspect of cognitive dysfunction may be relatively small. People with this particular problem might note difficulty adapting to change in the work place.
Identifying Cognitive Impairment and Its Causes
Sorting out various factors that contribute to cognitive dysfunction is essential. For example, memory and attention problems may be caused by depression, and the incidence of depression in MS is particularly high. Other potential causes of cognitive complaints include sleep problems, fatigue, stress, other medical conditions (such as thyroid abnormalities) and medication side effects. A partial list of medications that might worsen or cause cognitive problems follows: Ditropan (oxybutin), Detrol (tolterodine), Neurontin (gabapentin), Dilantin (phenytoin), Valium (diazepam), Klonopin (clonazepam), Baclofen (lioresal), Zanaflex (tizanadine), Deltasone (prednisone), and Decadron (dexamethasone). Many causes of cognitive dysfunction can be addressed or treated once identified. For this reason, careful evaluation is critical. Those with concerns about cognitive dysfunction should discuss the issue with their health care provider. Under some circumstances, a referral to a specialist, a neuropsychologist, who has training in both neurology and psychology, will be useful.
Prevention and Treatment
Preventing cognitive decline in MS, obviously, is an important goal. Whether current FDA-approved MS therapies can prevent cognitive dysfunction has received only limited study.
There is a large and growing body of evidence to support the idea that a lifetime of exercise can result in preservation of a number of aspects of cognition. Much of this literature has focused on aerobic exercise such as walking, running, bicycling and swimming. There are several possible mechanisms by which physical activity could affect cognitive function, including increasing blood flow to the brain, reducing the risk of heart disease and for stroke, and stimulating the growth and survival of brain cells.
In addition to exercise there are a number of other general strategies for reducing age-related cognitive decline. These may include maintaining low blood pressure, avoiding obesity, controlling stress and depression, pursuing a life of mental stimulation, and eating a diet rich in antioxidants from fruits and vegetables.
Cognitive problems often improve with cognitive or language rehabilitation programs provided by trained speech/language pathologists. These specialists can help patients understand the different types of cognitive problems that are being experienced and help develop strategies to alleviate them. If depression or anxiety are involved, simultaneous treatment with medications or counseling may increase the gains made in cognitive rehabilitation.
Assistive technology can also help address cognitive challenges:
- For many, a combination of low-tech and high-tech systems can support the cognitive needs in their lives. Often, this ends up being an array of notebooks, alarms, sticky notes, lists, calendars, and smart phones.
- Pocket Endeavor Suite (AbleLink Technologies, Inc.) supports organization and memory and is the first fully-integrated solution on a phone or handheld device to comprehensively address cognitive function.
- Arlene Carey von Linden, a Facebook fan, uses Google Calendar. “I have it on my computer and my phone and if I enter something, a neurologist appt for instance, into it on my phone it shows up on my computer too and vice versa. So no matter whether I’m at home or out and about my calendar is up to date and right at hand. I also have it set to alert me to appointments and such an hour ahead of time. Love it!”
- Patrice Snell Steiner, another Facebook fan, uses an iPod as a handheld organizer. “My family calls it (the IPod) Mom’s Brain. Actually, a good paper planner works, too — but my iPod keeps my calendar and myriad notes neat, alphabetized (or sorted by date when I need it), and accessible. The alarms have saved me from fiasco many times. I agree with my family: It’s the next best thing to a brain!”
- Brain games can help increase neural pathways, which studies show may help decrease disability. Lumosity.com has been clinically proven to support brain health. Designed by neuroscientists, this web-based training program makes brains smarter, faster and more flexible.
- A free smartphone app, TrackMyShots, is now available to help ease the log-keeping of patients requiring frequent injections.
Many people with MS will not experience cognitive problems. Furthermore, when cognitive problems do occur, they are often mild and sometimes affect only certain aspects of cognition.
There is both clinical evidence and a logical basis to assume that MS-related cognitive decline can be slowed by medications. Those with concerns about cognitive dysfunction should consult their health care providers. Identifying the complex factors that might be involved is a critical step in treatment.