Cognitive Dysfunction in Multiple Sclerosis
Other Rare Causes of Dementia
by Clive Evers
There has been a lot of recent research into changes in cognition due to MS and it is now evident that such changes do occur and that they are more common than was previously thought. Cognition is about our abilities in thinking things through and how well our memory works.
Cognition is also about how to focus and to maintain our attention; the way we learn and remember new things; how we think reason and solve problems. It also concerns how we plan and carry out our activities; the way we understand and use language and how well we recognise objects, assemble things together and judge distances.
The brain damage in MS is different to that in e.g. Alzheimer’s type dementia and so the problems shown are different. Although the problems may not amount to full dementia they can cause significant disruption to the lives of patients. In studies of MS patients with and without cognitive dysfunction, those with have been shown to be more significantly impaired with respect to work, sexual and social functioning and basic activities of daily living.
Multiple Sclerosis (MS)
Symptoms and course
Cognitive decline in MS generally does not correspond with either disease duration or physical ability. This may be explained by the unpredictable nature of damage to the myelin. Some patients may have had MS for many years without physical disability but others will be severely affected and confined to a wheelchair early on. Current research shows that the main determinant of the rate of cognitive decline is not the course of the disease but the extent of the development of brain lesions to the myelin. This can vary in patients with relapse/remission and those with a progressive condition. Cognitive dysfunction can be an early sign of MS and of brain lesions but progression is difficult to predict. Follow up studies of patients’ show that in some people there has been no or little further cognitive decline after 2, 4 or 5 years.
When someone with MS has cognitive problems their family and friends may be affected as well. There are a range of issues that may arise. The key to coping with them is to understand and to accept what is happening as a result of the disease process and possibly make some changes to make life easier. Carers may become frustrated if the person doesn’t respond to a question as quickly as the person is being awkward but in fact they just cannot remember or think straight.
The person may express anger about what is happening to them and take this out on the carer. Similarly the carer may also be angry or depressed about he person and possibly become irritable and withdrawn.
Causes and risk factors
MS is the most common disabling neurological condition among young adults (in the UK) and around 85,000 people are affected. MS is the result of damage to the myelin-a protective sheath surrounding nerve fibres of the central nervous system. This is part of the ‘white matter’ of the brain as opposed to the grey matter, which contains the nerve cells themselves. For some people MS is characterised by period of relapse and remission while for others it has a progressive pattern.
It is now accepted that approximately 45-60% of patients with MS have evidence of cognitive decline. For the majority of these people the changes are mild to moderate rather than severeWhilst brain lesions can result in more permanent cognitive problems there are a several factors that can interfere with or impair cognition temporarily. Depression, stress, pain, tiredness and relapses can create temporary cognitive difficulties.
Additional circumstances that can affect concentration, memory and learning include high alcohol consumption, poor nutrition and illnesses as well as medication that affects the central nervous system like tranquillisers, sleeping pills and painkillers.
Lifestyle change can also affect cognition. When patients experience cognitive problems it does not mean that they will experience all of them. There is much variation in the difficulties people experience and the impact it they will have on their lives. Learning and memory: the most common types of memory problems are remembering recent events and the need to do things. Some people say that it may take more time and effort to remember this affecting recall.
However, problems with language, recognition and spatial judgements e.g. distances are not so frequent in people with MS.People with MS rarely have problems with other types of memory and can remember skills, general knowledge or things about the past. Their memory problems are different to those who experience Alzheimer’s disease. Most often people with memory problems due to MS will continue to know who they are have no difficulties with communication and are able to carry out normal daily activities. Attention, concentration and mental sped: some people find it more difficult to concentrate for long periods of time or have trouble keeping track of what they are doing if interrupted. Problem solving: some people experience difficulties when making plans and solving problems. They know what they want to do but find it difficult to know where to start and what steps to take to achieve their aims. Word finding: people with MS may also experience some difficulties in finding the right word at the appropriate time in discussion.
Patients and their carers are encouraged to report repeated cognitive problems to their doctor as it may be a symptom of MS or due to other causes. MRI is the favoured brain imaging technique used to identify the brain lesions. It is safe and does not have an adverse effect on cognition. Studies that have looked for links between brain abnormalities and cognitive dysfunction have used two approaches in analysing the MRI data. These have been the use of rating scales and direct computer assisted lesion volume measurement. Little use has been made of PET scanning for diagnostic purposes and this reflects the difficulties in using this technique when the damage to the brain white matter is so widespread. Comprehensive neuropsychological testing can be complex for the purpose of cognitive screening. However combinations of tests (4, Rao) have been developed to examine long-term verbal and spatial memory,verbal fluency and speed of information processing.. These tests have been shown to have high sensitivity (71%) and specificity (94%) in detecting cognitive impairment in people with MS.
Care and treatment
A neuropsychological assessment will assist in identifying the problems the person is experiencing and make potential treatment easier.The assessment will consist of an interview about the past and present social functions and abilities of the person; a number of different verbal and written tests on attention, memory, problem solving and giving feedback on the results. The assessment will usually take between two and three hours with a follow-up session for feedback. The assessment should aim to identify the specific problems of the person and also their personal strengths to help them overcome and manage any weaknesses. Rehabilitation will aim to minimise the effects of problems with memory and thinking. It will include encouraging the person to practise and improve weakened skills; make better use of strengths; learn alternative and compensatory techniques; cope with limited abilities practically and emotionally and offer counselling to relatives. Goals may be set for the person based on the outcome of the assessment. Rehabilitation may be carried out in an individual or group setting.Voluntary agencies have further information of hints and tips for coping with cognitive problems.
Ongoing research/Clinical trials
There is a lot of research taking place in to Multiple Sclerosis and considerable research has been undertaken on cognitive function and MS. Worthy of note here is a major international review of research published in November 2002 which was highly critical of three decades of research effort. The review led by Prof. Peter Behan concluded that there is little evidence to support the accepted scientific assumption that MS is an autoimmune disease. The review offered further clarification to the effect that MS is a neurodegenerative and metabolic disorder, with the predominant genes being on chromosome 17, thus assisting in the hunt for the cause of the disease.
Voluntary organisations can provide advice, support and practical help in a range of areas:
Multiple Sclerosis International Federation www.msif.org
MS Society www.mssociety.org.uk
- MS, memory and thinking. Multiple Sclerosis Society (UK). November 2002
- Feinstein, A. Cognitive dysfunction in multiple sclerosis. IN Burns etc Textbook –check ref. pp 854-859
- DeSousa, EA et al Cognitive impairments in multiple sclerosis: a review.American Journal of Alzheimer’s Disease; 17(1); pp 23- 29.
- Foong, J et al A comparison of neuropsychological deficitis in primary and secondary multiple sclerosis. Journal of Neurology, 247, pp 97-101
- Kujala, P et al The progress of cognitive decline in multiple sclerosis. Brain 120, pp.289-297
Last Updated: vendredi 09 octobre 2009