The most accurate knowledge about progressive supranuclear palsy (PSP) comes from small sample studies that preclude precise estimation of the proportion of PSP patients affected with various symptoms and the examination of factors predicting survival time.
Cognitive Neuroscience Section, Henry M. Jackson Foundation and Medical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1440, USA.