Progressive supranuclear palsy.

Progressive supranuclear palsy (PSP) or Steele-Richardson-Olszewski syndrome is a neurodegenerative disease of middle and late age. It is under-diagnosed not only by general physicians but also by neurologists. The cause of PSP is not known. Exposure to toxins and viruses has been proposed in the aetiology of PSP without any concrete evidence. The features of PSP resemble those of Parkinson's disease and the two diseases are often confused. Corticobasal degeneration and multisystem atrophy are other differential diagnoses. Despite certain common features with Parkinson's disease, corticobasal degeneration, and mutisystem atrophy, there are important differences that help to differentiate it from these disorders.