Research studies on cognitive function in MS have demonstrated that as many as 50 to 66 percent of people will experience some cognitive changes over the course of the disease. Even though the severity of these changes can vary from mild to quite severe, the majority of these changes are in the mild-to-moderate range.
It's important to familiarize yourself with the kinds of changes that can occur because:
- Cognitive changes can occur at any time, and their severity doesn't appear to correlate with either length of time since diagnosis or the level of a person's physical disability. For example, a person with significant physical limitations, who has had MS for some time, can be totally free of cognitive symptoms, while a person with a recent diagnosis and few physical symptoms can have significant cognitive impairment.
- Even relatively mild symptoms can have a pretty big impact on various activities of daily living. For instance, people with MS are more likely to leave the workforce because of cognitive symptoms and fatigue than because of mobility problems! Early departure from the workforce is a critical issue for people with MS, but it can often be avoided with adequate symptom management.
- Cognitive fatigue can interfere with your ability to get things done. Research has shown that people with MS who are concentrating very hard on a cognitively strenuous task can experience a kind of mental fatigue that feels like acute "brain drain." Fortunately a brief rest from the task will generally help you get back on track.
- Cognitive changes tend to progress slowly over time. Even though MS relapses can include a sudden worsening of cognitive symptoms as well as physical ones, which tend to improve as a relapse ends, problems with thinking and memory don't generally disappear completely.
- The sooner these kinds of cognitive problems are identified, the easier it is to develop effective strategies to manage them. Small problems are always easier to work around than bigger ones. When you're able to put your finger on a problem with thinking or memory early on, you can find ways to compensate for it before the problem begins to interfere significantly with your daily life.
Like the physical symptoms that can occur in MS, the cognitive changes are highly variable from one person to another. One person may experience a lot of problems while another person experiences none or very few. In other words, no two people experience the same changes in exactly the same way. However, the following types of problems are the most common in MS.
Memory
Until fairly recently, experts believed that the primary memory problem for people with MS was with the retrieval of information that had been stored in memory. In other words, these experts believed that a person could learn new information and tuck it away in memory, but then be unable to recall or retrieve it from storage when needed.
More recent evidence suggests that the problem may involve the initial learning phase. People with MS may need longer time or a few more repetitions to learn and store new information successfully. After it has been stored, however, it can generally be recalled without difficulty. For example, if you have memory problems, it may take you longer than someone without memory problems to memorize a list of words. But once you have the words memorized, you'll remember them just as well as the other person does.
Information processing
Slowed processing is important because it may be the primary reason why a person with MS needs more time or repetitions to learn new information. When processing is impaired, the person has trouble keeping up with incoming information, whether it's from conversations, TV shows, or books. People describe this slowing by saying, "I can still do everything I used to be able to do, but it all seems much slower — like my brain needs to be oiled."
Attention and concentration
Attention and concentration, which form the basis for many other cognitive functions, can also be impaired by MS. For example, people who are used to being able to focus on many complex and competing tasks at the same time may notice some frustrating changes, such as being easily distracted by interruptions or competing stimuli, having difficulty moving smoothly from one task to another, or finding it more difficult to multi-task (an essential skill in any occupation, particularly parenthood).
Executive functions
Executive functions include the high-level processes of planning, prioritizing, and problem-solving. Research has shown that people with MS may find thinking through complex problems or projects more difficult because they lose the mental agility to shift from concept to concept along the way. People often describe this impairment as "feeling stuck" or "lost in a maze."
Visual perceptual skills
Visual perceptual skills, which include simple perception or recognition of objects, as well as sense of direction and orientation in space, can be affected in MS. These problems can interfere with activities ranging from reading a map or driving, to programming your VCR or dealing with those pesky "some assembly required" projects.
Verbal fluency
Verbal fluency includes the ability to find the word you're looking for quickly and easily. "It's on the tip of my tongue" is a particularly common complaint from those who have MS, as is "I'm talking to someone and all of a sudden I'm stuck without the word I need." People who experience these kinds of problems may feel less confident about their ability to talk smoothly and comfortably with others.
General intelligence
People with MS sometimes say they feel "dumber." The good news is that general intelligence is usually not affected in MS. However, individual functions that make up general intelligence, such as memory, reasoning, or perceptual skills, can be affected or slowed temporarily during a relapse or more permanently over the course of the disease. So, a person's intelligence quotient (IQ), which is a composite score made up of individual subtest scores on all these functions, can become lower over time.