A variable effectiveness of reparative and recovery mechanisms following tissue damage is among the factors that might contribute to explaining resolution of symptoms and maintenance of a normal level of function in patients who have multiple sclerosis (MS). The application of functional MR imaging in MS has shown that cortical changes do occur after white matter injury and that these changes can contribute to limiting the clinical outcome of such damage. Conversely, the failure or exhaustion of the adaptive properties of the cerebral cortex with increasing disease duration and burden might be among the factors responsible for the accumulation of fixed neurologic deficits in patients who have MS.