On the English (1931) and Spanish (1932) translations of von Economo's classic monograph on encephalitis lethargica.

The "second" seminal monograph by Constantin von Economo on encephalitis lethargica appeared in print in German in 1929, following his initial report of the disease (eponymously associated with his name) before the Viennese Society of Psychiatry and Neurology and the publication of his "first" monograph on the subject in 1917. The 1929 book was translated into English and Spanish and published by Humphrey Milford in Oxford and Espasa-Calpe in Madrid in 1931 and 1932, respectively. The present article gives some details of those translations and the neuropsychiatrists who produced them. Moreover, four previously unpublished letters by von Economo are presented, relating to the English edition of Die Encephalitis lethargica. These letters are of historical interest, as they provide insights into von Economo's personality and view of the translation.