Disturbed function and plasticity in multiple sclerosis as gleaned from functional magnetic resonance imaging.
OBJECTIVE
This review is intended to provide an up-to-date summary of the main functional magnetic resonance imaging studies conducted in patients with multiple sclerosis, and to show how such studies are changing our views on the ability of the multiple sclerosis brain to limit the clinical consequences of irreversible structural tissue damage.


RESULTS
Brain cortical reorganization is a common phenomenon occurring in patients with multiple sclerosis, independent of disease duration and clinical phenotype, which can be elicited by macroscopic lesions, as well as by the presence of 'occult' multiple sclerosis-related damage of the brain and cervical cord. An increased recruitment of the cerebral networks involved in the performance of given tasks might represent a first step in cortical reorganization with the potential to maintain a normal level of function in the course of multiple sclerosis. The progressive failure of these mechanisms, because of accumulating tissue damage, might, on the one hand, result in the activation of previously silent 'second-order' compensatory areas, and, on the other, contribute to the accumulation of irreversible disability.


CONCLUSIONS
Functional magnetic resonance imaging has the potential to provide important information about cortical reorganization following multiple sclerosis-related tissue damage, which should improve our understanding of the factors associated with the accumulation of irreversible disability in this disease. The enhancement of any beneficial effects of this cortical adaptive plasticity should be considered as a potential target of therapy for multiple sclerosis.
Filippi
Massimo
M
Neuroimaging Research Unit, Department of Neurology, Scientific Institute and University Hospital San Raffaele, Milan, Italy. m.filippi@hsr.it
Rocca
Maria A
MA
D002540:Cerebral Cortex / Q000503:physiopathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D009103:Multiple Sclerosis / Q000503:physiopathology*; D020528:Multiple Sclerosis, Chronic Progressive / Q000503:physiopathology; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000503:physiopathology; D009473:Neuronal Plasticity