Molecular Imaging of Extrapyramidal Movement Disorders.

Extrapyramidal movement disorders including Parkinson disease, multiple systems atrophy, progressive supranuclear palsy, and corticobasal degeneration are neurodegenerative syndromes with distinct neuropathological changes, indicating differing underlying etiologies. Clinical features that may distinguish among these conditions are often absent, particularly early after the onset of symptoms. Therapy is presently limited, and there are no established disease-modifying or neuroprotective interventions. Advances in therapeutics will depend on the early and accurate diagnostic classification of patients. Existing molecular imaging approaches demonstrate ability to separate several of these syndromes, but are clinically underutilized or are available only in research settings. The development of additional, specific imaging approaches targeting the misfolded protein deposits that characterize these neurodegenerative pathologies promises to advance not only the sensitive and specific endophenotyping of patients, but may also serve to measure directly potential therapeutic responses in the initial evaluations of new treatments.