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Cognitive Impairment in Multiple Sclerosis – Recent Advances and Future Prospects

European Neurological Review, 2010;5(1):69-72 DOI: http://dx.doi.org/10.17925/enr.2010.05.01.69

Abstract:

Multiple sclerosis (MS) is characterised not only by physical disability but also by gradual cognitive impairment. A large proportion of patients exhibit signs of cognitive deficit that negatively affect their quality of life. Reduced processing speed is often seen with the disease and several tests have been developed to measure its severity, including the Paced Auditory Serial Addition Test (PASAT) and the Symbol Digit Modality Test (SDMT). Long-term memory function is also commonly impaired in MS and studies suggest problems in primary registration of information. Also affected are executive functions used in novel planning and problem-solving. To evaluate cognitive function, cognitive test batteries with varying effectiveness have been introduced. The correlation of cognitive performance with magnetic resonance imaging (MRI) results remains inconsistent as multiple pathologies lead to the observed impairments. Therefore, combinations of MRI data are most successful at predicting deficiencies. The efficacy of current MS treatments in terms of cognition is unclear, making their clinical evaluation a great unmet need; the same is true of universal, validated cognitive measures that can be easily administered to MS patients around the world.
Keywords: Multiple sclerosis, cognitive impairment, memory loss, executive functions, cognitive test batteries, rivastigmine
Disclosure: Dawn Langdon has received research support from Bayer Schering Pharma AG/Bayer HealthCare Pharmaceuticals and honoraria from Bayer Schering Pharma AG/Bayer HealthCare Pharmaceuticals, Biogen, Hoffman La Roche, Merck-Serono, Novartis, sanofi-aventis and Serono Symposia, and has been contracted as a cognitive expert on studies for Bayer Schering Pharma and Merck-Serono.
Received: June 15, 2010 Accepted: July 02, 2010
Correspondence: Dawn Langdon, Department of Psychology, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK. E: D.Langdon@rhul.ac.uk

The Extent of Cognitive Impairment in Multiple Sclerosis

In his original characterisation of multiple sclerosis (MS), Jean Martin Charcot noted a loss of memory and reduced understanding,1 but this wisdom was overlooked for a century. It is only since the early 1980s that cognitive impairment in MS has begun to be scientifically investigated and understood.2

In part this may be because reduced functioning in the context of complex physical disability may seem reasonably attributable to physical impairments. In addition, the typical pattern of cognitive deficits in MS, with intact language masking inefficiencies in concentration, memory and reasoning, may escape casual (or even clinical) observation.

The prevalence of cognitive impairment in large heterogeneous groups of MS patients has been demonstrated by formal psychometric assessment to be 43–70%, with the higher prevalence rates from clinic samples.3 Cognitive impairment has been reported at all stages and in all subtypes of the disease. In the comparative study by Potagas et al., the cognitive impairment prevalence rates were 27.3% in clinically isolated syndrome (CIS), 40.0% in relapsing–remitting MS (RRMS), 56.5% in primary progressive MS (PPMS) and 82.8% in secondary progressive MS (SPMS).4 A cognitive impairment prevalence of 45% has been demonstrated in benign MS.5 Cognitive impairment tends to progress over time, but rarely in the space of a few years.6

The Impact of Cognitive Impairment in Multiple Sclerosis

Cognitive impairment has been shown to have an adverse effect on the lives of people with MS, over and above that imposed by their physical impairments. Cognitive impairment leads to reduced employment, social function,7 physical independence, sexual function,8 progress in rehabilitation,9 everyday life activities,10 safety in driving11 and adherence to medication.12 Poorer self-reported scores on formal measures of quality of life have also been linked to cognitive status. Reduced information-processing speed has been associated with lower quality of life.13

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Keywords: Multiple sclerosis, cognitive impairment, memory loss, executive functions, cognitive test batteries, rivastigmine