Cortical lesions important determinants of MS disability
medwireNews: Cortical lesions (CLs) may correlate with multiple sclerosis (MS) disability even more closely than white matter (WM) lesions do, a study shows.
The finding “supports the notion that assessments of inflammatory WM pathology alone provide an insufficient appraisal of the pathology responsible for disability in MS”, write the researchers in JAMA Neurology.
CLs were frequent in their study, found in 35 of 36 patients examined with 7-T magnetic resonance imaging (MRI) at a single centre. There were a median of 16 CLs per patient, compared with a median of zero lesions in 15 healthy controls, and they were most common in the six patients with primary or secondary progressive MS, at a median of 31.5 versus 14.5 in the 30 patients with relapsing-remitting MS.
The most common type of CL was leukocortical, defined as lesions involving both WM and grey matter. Across all patients, these occurred at a median of nine per patient.
Intracortical lesions involved only grey matter, and subpial lesions were “widespread areas of signal abnormality extending inward from the pial surface”. Both of these lesions occurred at a median of three per patient. All three lesion subtypes were more frequent in patients with progressive than relapsing-remitting MS.
Daniel Harrison (University of Maryland, Baltimore, USA) and co-researchers found that both the CL count and the CL volume significantly correlated with patients’ scores on the Expanded Disability Status Scale (EDSS), at respective correlations of 0.63 and 0.59. Correlation was stronger for leukocortical lesions than for the other two subtypes.
Moreover, the magnitude of the correlation between lesion volume and EDSS scores was nearly twice as large for CLs as for WM lesions, which had a correlation coefficient of 0.36.
CL count and volume, chiefly of the leukocortical subtype, also correlated with Multiple Sclerosis Functional Composite scores, whereas WM lesion volume did not.
And, after adjusting for age and gender, CL volume was associated with a significantly increased likelihood of cognitive impairment, with leukocortical lesion volume again being the main driver of the relationship.
In a related editorial, Robert Naismith (Washington University, St Louis, Missouri, USA) suggests that CL assessment should now be incorporated into clinical trials, noting that the increasing number of centres with 7-T MRI scanners would make a trial substudy possible “at select sites with 7-T expertise.”
He says: “Whether our treatments work differentially on white matter vs CLs or subpial vs leukocortical CLs has tremendous implications for the manner in which we approach MS care.
“From a therapeutic viewpoint, we need to understand whether we are treating just 1 disease process common to both gray and white matter or, potentially, multiple disease processes that are independent and dissociated from the beneficial therapeutic effect observed for white matter lesions.”
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