Update on epidemiological aspects of progressive supranuclear palsy.

The cause of progressive supranuclear palsy (PSP), the most common form of the atypical parkinsonian disorders, is unknown. PSP is characterized by four-repeat tau aggregates in neurons (neurofibrillary tangles) and glia in specific basal ganglia and brainstem areas. A thorough literature review led us to hypothesize that genetic and/or environmental factors contribute to its development. It is likely that inheritance of the H1/H1 tau genotype represents a predisposition to develop PSP requiring other environmental or genetic factors. Less likely, a relatively rare mutation with low penetrance could contribute to the abnormal tau aggregation present in this disorder. The possible role of chemicals in the diet or occupation, hypertension, traumatic brain injury, coffee, and inflammation or oxidative injury are reviewed.