Brain Atrophy

Traditionally, multiple sclerosis (MS) has been characterized mainly in terms of the associated inflammation and demyelination. However, recent evidence demonstrates that axonal damage, and cerebral atrophy also occur to a significant extent, even early in the disease. A number of these studies have established strong correlations between disability and atrophy of the brain stem or upper spinal cord, but correlations with cerebral atrophy are not as clear, at least in part due to the difficulty of measuring cerebral atrophy and to the fact that clinical deficits only loosely reflect the extent of the underlying cerebral pathology. In as much as progressive brain atrophy represents irreversible brain damage and tissue loss, a metric of brain atrophy is a powerful surrogate for the accumulated burden of disease. We feel that brain atrophy metrics will prove to be viable, precise, and clinically relevant measures of disease burden in MS. Atrophy measures will lead to a better understanding of MS pathology and will have important implications for disease prognosis, and monitoring treatment effect in clinical trials.

Our technique is based on the automatic estimation the BICCR (brain to intracranial capacity ratio). This measure depends on the estimatation of the grey-matter (GM), white-matter (WM) and cerebrospinal fluid (CSF) intra-dural volumes from in vivo MRI data (see Fig. below).

Fig 1: The first row (left to right) shows four transverse slices, starting just above the cerebellum, and ending above the centrum semiovale, taken from the stereotaxically resampled patient T1-weighted MRI volume. The second row shows the contours of the automatically extracted dural surface overlaid on the corresponding classified data. The BICCR is computed as the ratio WM+GM/(WM+GM+CSF) of all voxels within the dural contour. Note that all computations are done in 3D even though only 2D images are shown here.

Last modified: October 12th, 1999 Comments or suggestions to louis@bic.mni.mcgill.ca