Lethargia, lethargus, nona, encephalitis lethargica: The long history of a mysterious malady
Disorders of sleep have always aroused curiosity and fear, and most cultures record incidents of preternatural sleep, often associated with innocence or preservation of virtue. Hippocrates was probably the first to produce a rational medical account of such disorders (lethargos), but there has been a great deal of debate as to whether this disorder can be reconciled with any known to modern medicine. Lethargus was a difficult term even for classical authorities, and its meaning shifted with time and author, and by early modern times had been joined by related concepts of impaired consciousness, including cataphora, coma and carus. Discussions of such phenomena, both as autonomous entities and components of other disorders, occupied a great deal of space in medical textbooks until the 19th century, at which point lethargy as such began to disappear from medicine, although never completely. In 1890, a mysterious disorder known as nona appeared in Central Europe; it was temporally associated with the great influenza pandemic of the early 1890s. This was followed in 1916 by the appearance in Europe of encephalitis lethargica, similarly associated with an influenza epidemic (although a causal link was never unambiguously established), and which apparently disappeared as an epidemic disease in the mid-1920s. This overview of historical sleep disorders will address the question of what such prominent (apparently) neurological disorders may have represented, and whether they have actually disappeared or rather been re-defined.
Session V. Movement Disorders
Pavia, Italy, 2006