From hysteria to gait dementia: History of the concept of astasia-abasia.

Paul Blocq (1860-1896) and his teacher Jean-Martin Charcot (1825-1893) introduced the expression "astasia-abasia" into medical terminology in 1888 to designate a pathology they believed to be caused by hysteria. This condition makes it impossible to remain erect and to walk, whereas the ability to move the legs while lying down remains normal. At the turn of the 20th century, and now almost exclusively, this motor disturbance is recognised as a syndrome with multiple possible organic causes, and now described as "higher-level gait disorder". After briefly mentioning earlier descriptions by other authors, I will review Charcot's Tuesday lessons in 1889 that covered astasia-abasia and elucidated the beginnings of the breakdown into organic aetiologies: medial-frontal and corpus callosum tumors, damage to the cerebellar vermis, lacunar state as described by Pierre Marie (1853-1940), Parkinson's disease, and Parkinson-plus syndrome. The long history of astasia-abasia reveals a cluster of neurologists, often emerging from oblivion herein and all of whom, through the precision of their clinical examinations and their pathophysiological findings, helped advance the understanding of the mechanisms by which human beings are the only erect, constantly bipedal mammals, whether immobile or walking.