Corpus callosum index correlates with brain volumetry and disability in multiple sclerosis patients

Objectives:To analyze the correlation between corpus callosum index (CCI), brain volumetry, and disability in multiple sclerosis (MS) patients. The brain volumetry consists of the corpus callosum, cortical gray matter, subcortical gray matter, and white matter volumes.Methods:This was a retrospective cross-sectional study from October 2018 to February 2019 of 30 patients with MS aged 20 to 61 years old. Brain volumetry was performed using FreeSurfer© software. The CCI were measured manually using conventional best mid-sagittal T1W brain MRI. The anterior, posterior, and medium segments were measured and divided to its greatest anteroposterior diameter. Higher CCI values indicated greater corpus callosum volumes. Clinical evaluation was comprised of MS subtype, age of onset, relapse frequency and Expanded Disability Status Scale (EDSS).Results:Thirty MS patients with median of age 22 years were included. Relapsing-remitting (RRMS) subtype were 73.3%. Very significant correlations were shown between the CCI and corpus callosum volume (CCV) (r=0.79; p<0.0001) and cerebral white matter volume (r=0.81; p<0.0001). Significant correlations were shown between the CCI and cortical gray matter volume (r=0.64; p<0.0001) and subcortical gray matter volume (r=0.69; p<0.0001). The CCI was positively correlated with age of onset and inversely with EDSS. The CCV and CCI were smaller in secondary progressive MS (SPMS).Conclusion:The CCI is easy and fast to obtain in conventional MRI and significantly correlated with brain volumetry, age of onset and disability in MS patients.

Multiple sclerosis (MS) is one of the most common neurological diseases of the central nervous system and has various clinical manifestations, affecting the sensory, motor, cerebellar, brainstem, and autonomic systems.1–4 The MS progression will lead to disability that can affect the quality of life. In 2013, the prevalence of MS was 33 per 100,000 globally, an increase from approximately 30 per 100,000 in 2008.5 Regarding the cognitive impairment, it has been found in a study by Rao et al6 a 45% frequency of cognitive impairment in MS patients. Furthermore, it has been found in several studies that the decline in visual and verbal episodic memory as well as decelerated cognitive processing speed are the most frequent cognitive domains impaired in multiple sclerosis.7 Between these 2 domains, it has been shown that memory impairment were slightly more common than those with memory impairment and processing speed impairment in 128 patients with relapsing-remitting MS (RRMS).8 In our previous study, we found impairments in the Symbol Digit Modality test (up to 50%), California Verbal Learning test-II (27.5%), and Brief Visuospatial Memory test-revised (32.5%) in MS patients.9Brain volume in MS patients were found to be significantly smaller compared to healthy subjects and associated with the progression of disability.10 Brain atrophy in MS can occur by 3 mechanisms: volume loss within the lesion itself, retrograde degeneration, and Wallerian degeneration in the remote area of the fiber pathway.4,11,12 Brain atrophy can be seen in earliest stages of MS (clinically isolated syndrome).13 Gray matter atrophy begins early in the course of the disease and is correlated with the progression of disability, especially motor and cognitive disability.14–16 Measuring brain atrophy has been proposed as one of several treatment monitoring parameters for MS.17The corpus callosum is one of the main white matter pathways and affected by the progress of chronic diseases, including MS.1,3,4 Corpus callosum damage is correlated with cognitive impairment and motor disability in MS patients. Corpus callosum atrophy could be a clinically relevant marker of cognitive impairment.18–20Brain volumetry using magnetic resonance imaging (MRI) is a useful, noninvasive tool in assessing subcortical morphometric changes as well as evaluating the regional neurological impact of psychopathology, such as dementia, psychiatric disorders, and normal aging.21 Some software packages have been developed for measuring brain tissue volume using MRI with semi-automatic segmentation, such as FreeSurfer© (The General Hospital Corporation, Boston MA, USA), FIRST (FMRIB’s Integrated Registration and Segmentation Tool), FSL (FMRIB’s Software Library), and SPM (Statistical Parametric Mapping).22With this background, the objective of this study was to determine the correlation between the corpus callosum index (CCI) measurements and the corpus callosum, cortical gray matter, subcortical gray, and cerebral white matter volumes determined through brain MRI volumetry and clinical characteristics in MS patients.