Contribution of MR imaging to understanding the pathophysiology of multiple sclerosis and Alzheimer disease

	Multiple Sclerosis	Alzheimer’s Disease
Disease pathophysiology	Neurodegeneration in addition to inflammation	Inflammation in addition to neurodegeneration
Diffuse structural tissue damage	Damage to normal-appearing white matter	Damage to normal-appearing gray matter
White/gray matter involvement	Damage to gray in addition to white matter	Damage to white in addition to gray matter
Earliest clinical phase	Prognostic value of multiple MR imaging lesions. Presence of neurodegeneration	Hippocampal atrophy as part of the “Alzheimer disease signature”
Cortical plasticity	Cortical reorganization following focal and diffuse tissue injury	Cortical reorganization possibly following plaque and tangle deposition
Monitoring treatment efficacy	MR imaging metrics are primary end points in phase II and secondary end points in phase III trials	MR imaging technology exploited only in most recent trials