ABSTRACT
The measurement of central nervous system (CNS) atrophy has become an important component in the growing set of imaging tools used to monitor multiple sclerosis (MS)1. Driven by the lack of correlation between lesion measurements and disability, the increasing focus on axonal loss as the major pathological substrate of progressive disability and the need to quantify damage in the normalappearing brain tissue, many researchers have investigated brain and spinal cord atrophy in MS patients. CNS atrophy is now widely regarded as an objective measure of global disease burden and an indirect measure of disease severity in MS. Like conventional lesion measurements, atrophy can be quantified using standard magnetic resonance imaging (MRI) acquired for routine examinations. However, in contrast to lesions, which only account for focal tissue damage and may represent reversible processes that resolve over time, atrophy reflects the end result of severely damaging pathological processes that occur focally within lesions and diffusely in normal-appearing brain tissue. Axonal damage and loss, chronic demyelination and gliosis result in a reduction in CNS parenchymal tissue
volume and a corresponding expansion of ventricles and sulci. These morphological changes associated with atrophy can be detected and quantified through the application of computer-aided image analysis techniques, even in the early stage of disease.
