Constantinescu_EU Neurology 11/03/2010 12:45 Page 70
Multiple Sclerosis
Conventional and Quantitative Magnetic Resonance Imaging and
Cognitive Impairment in Multiple Sclerosis
Christopher R Tench
1
and Cris S Constantinescu
2
1. Research Fellow; 2. Professor of Neurology, Division of Clinical Neurology, School of Clinical Sciences, University of Nottingham
Abstract
An estimated 30–70% of patients with multiple sclerosis (MS) have some cognitive impairment. Cognitive function depends on a spectrum of
faculties including information processing speed, sustained attention, recent memory and executive function. The broad definition of cognition
has resulted in different assessments of function, and repeatable batteries of tests have been devised to gain an overall and repeatable view of
cognition in MS. Many studies have attempted to find an association between cognitive function and MS pathology using magnetic resonance
imaging (MRI). Conventional MRI has been used to show the relationship between cognitive impairment and MS lesion volume and/or brain
volume (reflecting atrophy). Studies using quantitative MRI to estimate the degree of abnormality in tissue that is normal-appearing on
conventional MRI have also found correlations with cognitive function. Longitudinally, cognitive decline has been found to correlate with changing
MRI-detectable pathology in some studies. However, consistency between studies has been lacking, and the large number of cognitive tests
available makes direct comparison of different studies difficult. Focus on specific cognitive domains may alleviate this issue in future studies.
Keywords
Multiple sclerosis, cognitive function, magnetic resonance imaging, cross-sectional studies, longitudinal studies, quantitative imaging,
conventional imaging, attention, working memory
Disclosure: The authors have no conflicts of interest to declare.
Acknowledgements: The authors’ work has been supported in part by the University of Nottingham, The Multiple Sclerosis Society of the Great Britain and Northern Ireland
and the EU (Marie Curie International Fellowships).
Received: 4 January 2009 Accepted: 25 May 2009
Correspondence: Cris S Constantinescu, Division of Clinical Neurology, School of Clinical Sciences, University of Nottingham, NG7 2UH, UK.
E:
Cris.constantinescu@nottingham.ac.uk
Multiple Sclerosis area or volume. Despite accurately depicting the distribution of MS
Multiple sclerosis (MS) is a chronic inflammatory disease affecting the lesions, correlation with clinical measures such as the expanded
central nervous system (CNS) that is characterised by multiple areas disability status scale (EDSS)
4
is poor. Explanations for this
of demyelination, focal and diffuse inflammation, axonal damage and ‘clinico-radiological paradox’ include lack of pathological specificity,
loss and gliosis. The disease course falls into different broad clinical re-myelination and cortical plasticity. Another explanation is the lack
categories, including relapsing–remitting (RR), secondary progressive of spatial information in the lesion burden measures, location of the
(SP) and primary progressive (PP) MS. Patients who do not have lesion within the brain being paramount in determining effect.
clinically definite MS according to the criteria
1,2
but do have an
isolated event suggestive of MS are said to have clinically isolated Other conventional MRI measures have been used in an attempt to
syndrome (CIS). overcome some of the limitations of T
2
-weighted imaging. T
1
relaxation time contrast is thought to reflect more specifically axonal
Magnetic Resonance Imaging Measures in loss, so the apparent lesion burden may correlate better with
Multiple Sclerosis disability. Gadolinium-enhanced T
1
-weighted images are reported to
MS lesions can be visualised with remarkable clarity using magnetic show lesions where the blood–brain barrier has been breached, and
resonance imaging (MRI), which is used as a diagnostic tool and has indicate new or active lesions and therefore active disease. Tissue
also greatly improved our understanding of the mechanisms of MS by loss, or atrophy, has also been estimated using high-resolution
giving us the opportunity to study the pathology in vivo. There is vast images. This loss has also been found to correlate with disability to
literature on the use of MRI in the study of MS, the bulk of which has varying degrees.
focused on conventional MRI.
While conventional MRI has revealed much about the progression of
Conventional T
2
-weighted spin echo images reveal the lesions,
3
which the disease, its lack of pathological specificity has ultimately limited
appear hyperintense, most completely of the different contrasts. The its impact on our understanding of MS. Recent work has shifted
T
2
MS lesion burden has probably been the most commonly used MRI towards utilising new quantitative MRI measures. These allow the
outcome measure in large clinical trials, and is quantified by count, quantification of properties such as T
1
or T
2
relaxation time,
70 © TOUCH BRIEFINGS 2009
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