Rather than acute inflammation, long-standing multiple sclerosis (MS) course is hallmarked by relentless axonal loss and brain atrophy, both with subtle clinical expression and scarcely visible on conventional MRI studies. Brain atrophy imaging has sophisticated methodological requirements, not always practical and accessible to most centers. Corpus callosum (CC) is a major inter-hemispheric white matter bundle, grossly affected by long term MS and easily assessed by MRI (1).
CCI is an easy to use MRI marker for estimating brain atrophy in patients with MS. Brain atrophy as measured with CCI was associated with disability progression but it was not an independent predictor of long-term disability (2).
References:1. Figueira FF, Santos VS, Figueira GM, Silva AC. Corpus callosum index: a practical method for long-term follow-up in multiple sclerosis. Arq Neuropsiquiatr. 2007 Dec;65(4A):931-5
2. Yaldizli O, Atefy R, Gass A, Sturm D, Glassl S, Tettenborn B, Putzki N. Corpus callosum index and long-term disability in multiple sclerosis patients. J Neurol. 2010 Aug;257(8):1256-64