Impaired olfaction and Parkinsonism: A "hidden gem" in the neurological literature.

Though impaired olfaction in Parkinson disease is now a widely accepted characteristic of this disorder, this discovery arose from several international case reports preceding the first formal research on this topic (conducted in 1975 by Ansari and Johnson). The clinical observations have supplemented findings by Braak and colleagues demonstrating that, like impaired sense of smell, olfactory bulb involvement by Lewy pathology is a common early feature in Parkinson disease.