The Knud Krabbe (1885-1961)-Henry Alsop Riley (1887-1966) letters (1929-59): transatlantic friendship fostered by the international neurological congresses

The correspondence between Dr Knud Krabbe in Denmark and Dr Henry Alsop Riley in the USA, archived at Columbia University, provides valuable insight into the friendship that arose between these two early leaders in neurology who lived on opposite sides of the Atlantic. Comprised of 15 surviving letters, the correspondence began in 1929 but primarily spanned the period from 1954 to 1959 and during that time showed a very familiar tone between the two men. Their correspondence is not only about work but the range of topics evidences the warmth that evolved between the two men. Their friendship likely originated at the International Neurological Congresses (INCs), which occurred every four years. This paper serves to bring this correspondence, previously not well known, into the historical literature and includes personal and biographical information. It shows how the INCs, on a human level, resulted in links between the vanguards of neurology in different countries, thus helping to foster the development of neurology as an independent medical discipline during the 20th century.