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Cognitive Problems

About 50% of people with MS will develop some degree of cognitive dysfunction. In MS, this generally means slowed ability to think, reason, concentrate, or remember. But only 5-10% of persons with MS develops problems that are severe enough to interfere in a significant way with everyday activities. While cognitive dysfunction is more common among people who have had the disease for a long time, it can be seen early in the disease course - even as the first symptom.

MS may affect cognitive function for several reasons. First and foremost, MS damages both myelin and the nerve cells within the brain, thereby compromising a variety of functions handled by the brain. In fact, MRI studies have indicated that the extent of demyelination in the brain is related to severity of cognitive dysfunction. However, MS can also affect cognition indirectly. MS is often associated with depression, anxiety, stress and fatigue, all of which may compromise cognitive functioning. Fatigue can be particularly challenging to one's ability to sustain any type of challenging mental task.

Just as the physical symptoms of MS can vary considerably from person to person, cognitive changes can as well. Moreover, it is common for certain functions to be largely intact while others are more severely affected. The cognitive function most likely to be affected appears to be memory. Other cognitive functions frequently affected in MS include speed of information processing, executive functions (planning and prioritizing), visuospatial functions (impairment in visual perception and constructional abilities), abstract reasoning and problem-solving and attention and concentration - especially sustained attention and ability to divide attention between separate tasks. One of the most vexing cognitive deficits seen in MS is word-finding difficulty - the experience of having a word on the tip of your tongue but not being able to remember it.

The first signs of cognitive dysfunction may be subtle. The person may have difficulty in finding the right words to say, or trouble remembering what to do on the job or during daily routines at home. Decisions that once were easy now demonstrate poor judgment. Often, the family becomes aware of the problem first, noticing changes in behaviour or personal habits.

People with MS and their families should seek medical help if they are concerned about cognitive dysfunction. Even early in the disease, cognitive dysfunction can have an impact on role performance at home and at work. In fact, research has shown that cognitive symptoms and fatigue are two primary reasons for early departure from the workforce. Since cognitive function can also be affected by aging or medications, a careful evaluation is necessary to determine the cause of these mental changes.

To evaluate a person with MS for cognitive dysfunction, a specially trained health professional, neuropsychologist, administers a battery of tests. Based on these tests, the person's cognitive deficits and strengths can be determined. Strategies for coping with areas of deficit can usually be devised. For example, one strategy for dealing with memory problems is using a diary or hand-held computer to store information. In rare instances, cognitive dysfunction may become so serious that the person can no longer be cared for at home.

During the last few years, there have been numerous studies of ways to stabilise or improve cognitive dysfunction. Some of these studies have looked at whether the MS disease-modifying drugs can slow the progression of cognitive changes. Results thus far have been mixed, with interferon-beta 1a showing the most potential. However, since the disease-modifying drugs have all been shown to reduce the accumulation of new demyelinating lesions, it is likely that over the long term, they should all help to stabilise cognitive changes.

Other studies have explored the utility of rehabilitation for cognitive changes. Cognitive rehabilitation involves a variety of strategies and thus far the greatest promise seems to reside in the use of straightforward compensatory techniques, i.e. using organisation, diaries, computers, filing systems, etc. to compensate for memory deficits and other changes such as reduced planning ability.

Studies currently underway that are funded by the National MS Society are investigating the natural history of cognitive changes, along with better ways of diagnosing and treating cognitive problems seen in people with 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 significantly modify the course and impact of the cognitive changes seen in MS.

Cognitive problems in Multiple Sclerosis

DW Langdon, PhD

A. J. Thompson, MD, FRCP

The National Hospital for Neurology & Neurosurgery and The Institute of Neurology London, UK

Summary

Some people experience changes in memory, concentration and other mental skills, which together reflect the cognitive impact of MS. This aspect of the disease is increasingly recognised by people with MS, their carers and health professionals Cognitive difficulties do not only affect primarily mental tasks. Physical independence can also be compromised by cognitive problems. If cognitive problems arise, they are most likely to occur in the domains of memory, attention and reasoning. Less apparent than most physical disability, diminished cognitive skills can be a hard subject to broach, discuss and deal with. However, for those people with MS who experience the cognitive aspects, acknowledgment and understanding can be crucial elements of their social support system.

Introduction

Multiple Sclerosis (MS) is conventionally thought of as a disease that can bring physical disability, but cognitive function may not escape the effects of the disease. Cognitive difficulties may occur with memory, concentration and other mental skills. There are three reasons why information about cognitive aspects of the disease should be readily available to patients, carers and professionals:

There is a growing awareness of the impact of cognitive dysfunction on the everyday life of people with MS and it poses a challenge to both them and to the health care systems which provide rehabilitation services. The British Society of Rehabilitation Medicine gave cognitive dysfunction a high priority in the report of their Working Party on Multiple Sclerosis (1993). In their list of 15 areas of dysfunction that resulted in disability for people with MS, cognitive dysfunction was number 4, after locomotion, continence and emotional distress.

Cognitive control of physical activity

At first glance, it may seem that cognitive dysfunction is a separate problem to physical disability. But in fact, cognition has an important role in motor activity. Imagine for a moment, a robot designed to exactly imitate the physical properties of the human body its movements, joints, power and weight. Think how complex a task it would be to program the robot to move from a standing position beside a car, to being seated in the driver's seat. The robot body must move, taking account of weight transfers and range of movement limitation, without falling through the narrow space of the open car door, avoiding the steering wheel, to finish seated with both feet on the floor of the car in front of the driver's seat. A moment's consideration reveals this to be a complex task, although most people perform this movement effortlessly several times a day.

Then think of a person with one leg in plaster, perhaps as a result of an accidental fracture, moving from a standing position beside their car to being seated in the driving position. They have to bend their body and ease it past the steering wheel, before loading their leg and reaching across to shut the door. Suddenly the movement requires a great deal of concentration. They must take into account the new constraints that an artificially straightened leg imposes on bending and deceleration. It may not bear weight. They may have to guard against pain when they move. Their centre of gravity is shifted. Their movements are slower and, as a result, the momentum of their movements is changed and so the pattern of muscle power required to produce the movement must be modulated, from the familiar automatic programme that worked when they were physically healthy.

We have just considered the level of difficulty that a healthy brain would encounter trying to manoeuvre a body which has sustained a single, short-term, stable disability. For some people with MS, movement control is harder still. Their cognitive function may be inefficient. This could mean that their spatial processing has weakened and their judgment of distances is unreliable resulting in the need for mid-course corrections, which place further demands on balance skills and motor activity. Their planning may be affected and every different car (or seat of any kind) that they approach poses a new set of problems in terms of distances and physical organisation, that they can no longer solve effortlessly.

Just as there is an increasing need to be cautious, they are becoming impulsive and finding it hard to slow their movements to a safe speed. Those around them become concerned for their safety, but the person with MS may also have reduced insight or be fiercely independent and be unable to comprehend these worries. Along with these possible cognitive inefficiencies, must be added the additional cognitive load of monitoring a varying and unpredictable level of physical disability, where even time of day, temperature and preceding activity levels must be entered into the movement equation, to allow for the effects of fatigue. Clearly, even an everyday motor activity is influenced by cognitive dysfunction. For some people with MS, it is the combination of impulsivity and poor insight into their physical limitations that condemns them to a wheelchair, when their physical weakness and spasticity alone would not do so. Cognitive dysfunction in MS may not only compound the physical disabilities of a patient, it may accelerate them.

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How the disease process affects cognition

Although some areas of the CNS are more likely to host MS plaques (the optic nerves, the spinal cord and the white matter surrounding the ventricular system of both cerebral hemispheres), the pattern of development of these plaques in the CNS is almost random in the individual, which accounts for the unpredictability of the disease course and expression. Because cognitive difficulties are the result of the disease pathology, they too are individual and unpredictable. For example, although intellectual effects are not pronounced in most people with MS, some may suffer cognitive difficulties with little or no physical symptoms.

The measurement and treatment of cognitive difficulties is usually carried out by a neuropsychologist. The cognitive profile of a person with MS may not be easy for a neuropsychologist to determine despite using measures which have been standardised and validated for assessing people with diseases that affect the CNS. Most neuropsychological tests rely on a standardised administration and scoring of a mental task, which is then compared to the scores of a group of healthy people who are the same age as the person being assessed. Some tasks may be presented in a spoken question and answer format, others involve recognising photographs, re-ordering line drawings to tell a story, or arranging blocks to copy specified abstract pat-terns.

Some of the symptoms of MS, which are not primarily cognitive (such as motor and sensory deficits and fatigue) may affect how well a person with MS performs on some cognitive tests. The neuropsychologist must take account of the individual's physical symptoms, when selecting the cognitive test battery. For example, tests which require fine visual acuity or motor speed and coordination may not be appropriate for some people with MS. For neuro-psychologists attempting to research cognitive dysfunction, which involves the cognitive assessment of groups of patients, guidelines are available for test selection? These aim to ensure that the cognitive characteristics of each patient group are in a common currency, relatively unaffected by physical symptoms and thus directly comparable to the results of other clinical and research groups.

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The 'footprint' of MS

There has been a long history of reports of cognitive dysfunction in MS. Perhaps the most convincing is that of Canter (1951), who was able to conduct a prospective analysis in the 1950s by comparing the scores of recently diagnosed people with MS on the Army General Classification Test, with the scores that they had achieved four years previously as healthy soldiers. A significant decrease in scores was observed. With the advent of detailed imaging techniques, such as magnetic resonance imaging, cognitive dysfunction has been shown to relate to disease activity in the cerebral cortex.

However, cognitive dysfunction has only recently been recognised as a significant factor in the everyday life of many people with MS. Partly this may be because the pattern of cognitive difficulties is unique for each person with MS and its impact is determined by their own life circumstances and plans. Also, the recent recognition of this area may be the result of the pattern of cognitive difficulties that tends to occur in this disease. Referred to as the "footprint of MS", this pattern is of relatively preserved language and social skills, but sometimes marked difficulty with insight and problem solving. The competent language and social function of most people with MS (who may have other cognitive difficulties) means that in ordinary conversation, their difficulties may not be apparent. In some ways, the cognitive difficulty that may be associated with MS is a "sub marine problem", whilst to casual observation it may run silent, it also runs deep.

Experimental work has supported the view that some people with MS may have difficulty with concept formation and in deducing or learning new rules in psychological tests. The Category Test of the Halstead-Reitan Battery requires a person to deduce a rule which categorises many novel abstract designs, from the assessor's feedback to their trial categorisations. Whilst people with MS do no worse than other groups of patients with CNS diseases, they can be less efficient than healthy control subjects. Similarly on the Wisconsin Card Sorting Test (WCST), another task which requires a person to deduce a rule by which to categorise a limited set of abstract patterns, people with MS have done less well than controls.

In addition, difficulties with the WCST have been directly linked to focal disease activity. Arnett et al (1994) demonstrated that MS patients who had a similar number of plaques located elsewhere in the brain. Poor reasoning skills are often the most disabling feature of cognitive dysfunction in MS. This can result in the weakening of planning and initiation of action across a variety of time scales. It is our experience in the rehabilitation of people with advanced MS, that it is often essential to discuss immediate treatment and future plans in very concrete terms. It cannot safely be assumed that the implications of a course of action are clear to the person with MS and it may necessary to respectfully and tactfully discuss each potential outcome in very specific and concrete terms.

Problems with concentration can figure prominently in this disease and from a surprisingly early stage. Experimental studies with so-called "harbinger" cases, that is patients who have experienced one episode of optic neuritis and are thus at risk of going on to develop MS, show the attentional skills of the patients to be weaker than those of matched healthy control subjects. These types of studies illustrate small, statistical differences, that are undetectable to the individual in everyday life.

A study comparing diagnosed MS patients with matched control subjects demonstrated difficulties in the short term, or immediate attentional, memory of the MS patients. Although the everyday impact of poor attention may seem a small irritation, such as having to write down telephone numbers as they are spoken, instead of being able to hold them in the head whilst dialing, even a mild impairment can lead to significant disability.

We have recently treated a woman in her 30s who, on cognitive testing, demonstrated a comparatively mild attentional deficit and hardly any other neuropsychological impairment. But because her employment had been as a betting shop manageress, whose mental calculation of odds and payout's had to be quick and faultless, she had become unemployed. In more severe cases, attentional deficits can deplete leisure options, as the thread of a novel gets lost beyond recovery, or the plot of a favorite soap opera confuses rather than entertains.

Memory difficulties for people with MS have been widely reported in the literature and, like the general effects of poor reasoning in MS, their effects are insidious. A marked feature of the pattern of memory deficits in MS is that recall, or unprompted remembering, is more adversely affected than recognition, or prompted remembering.

This leads patients to respond appropriately to reminders from relatives or professional workers, but when not prompted, MS patients with this type of difficulty may fail to remember essential health care activities or appointments People with MS are less likely to volunteer problems to carers or health workers, unless that particular aspect is probed by a specific question. Recall memory can also let people down when it comes to the initiation of activity. They may report that things are fine during an interview, because the questions have prompted them to consider the problems that they are experiencing in everyday life, but when left to cope alone during the day, somehow the things discussed do not seem to happen as planned.

Understanding and acknowledgment

Although this article focuses on cognitive difficulties, they are not an inevitable part of MS. Many people with MS will experience no significant cognitive loss. However, for some, cognitive difficulties are among the manifestations of MS and a proper appreciation of the full impact of the disease cannot exclude this area. Cognitive dysfunction can be a hard subject to broach, even with family and friends. It is not immediately apparent, in the way that physical disability can be.

There may be only a partial appreciation of the problems by patients, carers and health professionals, each of whom have different perceptions of the changes that may have occurred. People often think that cognitive function is a single entity and so, for example, they fear that their failing to remember telephone numbers may mean that all aspects of memory and intelligence are compromised. This is hardly ever the case. Starting to discuss the problems, at the right time for those involved, can pay dividends in terms of reduced stress, improved coping and limiting the functional impact of the disease. For those people with MS for whom cognitive difficulties are an everyday problem, understanding and acknowledgment are important parts of their social support system.

References

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