Important observations prior to the description of the Hoover sign

To study the context in which Hoover described his sign for differentiating hysterical and organic hemiplegia.

At the turn of the 20th century, many physicians were looking for signs to distinguish organic from hysterical hemiparesis. In 1908, Hoover described his sign of "complementary opposition." Other signs based on associated movements of the upper extremities, lower extremities, and trunk were also described during and before this period and might have contributed to Hoover's understanding of complementary opposition.

A complete literature review of the original relevant articles by Babinski, Bychowski, Grasset and Gaussel, and Hoover was performed.

Several similar maneuvers were described before the Hoover sign. Babinski described the trunk-thigh test in 1897. Bychowski in Warsaw (performed since 1902, published in 1907) and Grasset and Gaussel in Paris (1905) independently described a phenomenon in which the separate elevation of each leg was performed more easily than simultaneous elevation. Moreover, Bychowski, although not emphasizing it as a sign, described what became known as Hoover sign. Hoover sign (1908) has been considered a further elaboration of these previous observations. Interestingly, Hoover had studied in Europe, and although no direct relationship between his discovery and these observations has been elucidated, the authors postulate that he was influenced by Babinski, Bychowski, and Grasset and Gaussel.

Although Babinski, Bychowski, and Grasset and Gaussel described similar signs, only Hoover sign is still in wide use by practitioners.