PAPER

Progression of non-age-related callosal brain atrophy in multiple sclerosis: a 9-year longitudinal MRI study representing four decades of disease development

Martola Juha¹, Stawiarz Leszek², Fredrikson Sten², Hillert Jan², Bergström Jakob³, Flodmark Olof¹, Kristoffersen Wiberg Maria⁴

¹ Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
² Division of Neurology, Huddinge, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
³ The Medical Statistics Unit, Department of Learning, Informatics, Management & Ethics (LIME), Karolinska Institutet, Stockholm, Sweden
⁴ Department of Radiology, Karolinska University Hospital, Stockholm, Sweden

Correspondence to:
Dr J Martola
Division of Radiology, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, SE-14186 Stockholm, Sweden;juha.martola{at}ki.se

Background: In multiple sclerosis (MS), multiple periventricular lesions are commonly the first findings on MRI. However, most of these MS lesions are clinically silent. The brain atrophy rate has shown better correlation to physical disability, but it is not clear how atrophy develops over decades. Corpus callosum forms the roof of the third and lateral ventricles. The corpus callosum area (CCA) in a midsagittal image is age independent in a normal adult population up to the seventh decade; therefore it can be used as a marker for non-age-related, pathological brain atrophy.

Objectives: To investigate whether and how CCA decreases in size over time in patients with MS.

Methods: In a clinical observational study, 37 patients with MS with a wide range of disease duration at baseline (1–33 years) were followed. Three different MS courses were represented. The mean of individual MRI follow-up was 9 years. Multiple sclerosis severity score (MSSS) was also applied to evaluate disability at baseline and after 9 years of follow-up.

Results: A significant decrease in CCA over 9 years (p<0.001) and a persisting association between CCA and the disability status were found. The atrophy rate was similar ever four decades of MS for all MS courses. The mean annual CCA decrease was 9.25 mm² (1.8%). Surprisingly, atrophy rate did not correlate with sex, disease duration, age at MS onset or MS course.

Conclusions: Serial evaluations of CCA might be a robust method in monitoring a non-age-related decrease in CCA, reflecting progression of irreversible destructive changes in MS.

Abbreviations: CCA, corpus callosum area; EDSS, Expanded Disability Status Scale; MISS, midline internal skull surface area; MS, multiple sclerosis; MSSS, multiple sclerosis severity score; RRMS, relapsing–remitting multiple sclerosis; SPMS, secondary-progressive multiple sclerosis

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