[en] Both the aging brain and neurodegenerative disorders are characterized by a lack of vital endurance of affected neurons resulting in their premature death. Neuronal shrinkage or atrophy and death are normal and inevitable aspects of normal or successful aging; this is unexpected, excessive, and premature in neurodegenerative disorders. These histologic changes result in the neuroimaging findings of focal and/or diffuse atrophy with consequent enlargement of cerebrospinal fluid (CSF) spaces. The aging brain and neurodegenerative disorders share other magnetic resonance (MR) changes, i.e., markedly hypointense extrapyramidal nuclei and hyperintense white matter foci. The sequelae of senescent vascular changes result in additional characteristic features of the aging brain. This paper presents the MR and neuropathologic manifestations of both the normal aging brain and the brain affected by neurodegenerative disorders