Application of fMRI to Multiple Sclerosis and Other White Matter Disorders

The variable effectiveness of reparative and recovery mechanisms following tissue damage is among the factors that might contribute to explain, at least partially, the paucity of the correlation between clinical and magnetic resonance imaging (MRI) findings in patients with white matter disorders. Among the mechanisms of recovery, brain plasticity is likely to be one of the most important with several possible different substrates (including increased axonal expression of sodium channels, synaptic changes, increased recruitment of parallel existing pathways or “latent” connections, and reorganization of distant sites). The application of fMRI has shown that plastic cortical changes do occur after white matter injury of different aetiology, that such changes are related to the extent of white matter damage, and that they can contribute in limiting the clinical consequences of brain damage. Conversely, the failure or exhaustion of the adaptive properties of the cerebral cortex might be among the factors responsible for the accumulation of “fixed” neurological deficits in patients with white matter disorders.