Magnetic resonance imaging of neurodegenerative diseases.

Magnetic resonance imaging (MRI) has become an important diagnostic tool in the evaluation of neurodegenerative diseases. Although MRI currently does not yield sufficient predictive power to provide a diagnosis in most individual cases, important features have been identified in population studies that help support or exclude a clinical diagnosis under consideration. In parkinsonian patients, putamenal signal hypointensity is commonly observed in patients with atypical parkinsonism. In demented patients, hippocampal atrophy and prolonged T2 relaxation may help identify individuals with Alzheimer's disease. Caudate and putamenal atrophy are seen in Huntington's disease and may serve as markers of disease progression.