200 years after Bouchet and Cazauvielh: revisiting early studies on Ammon’s horn sclerosis between 1825 and the turn of the century

Abstract Some 200 years ago, in 1825, French doctors first described their impressions of hippocampal alterations in epilepsy during autopsies. However, recognizing the fundamental role the mesial lobe would play in epileptology did not occur until many decades to follow. Following a gap in the scientific literature, Theodor Meynert in 1867 raised the topic of Ammon’s horn sclerosis (AHS) again, and a body of studies followed, many of them in the German-speaking literature. Some studies remain influential to the present day, such as the contribution by Sommer (1880), whose name is linked to sector CA1 of Ammon’s horn, or the work of Bratz (1899), who included the first detailed histological illustration of AHS. A row of early studies on AHS reflects the growing body of scientific evidence on the role of hippocampal pathology in a subtype of epilepsy, which was enigmatic in the past but today is well-known as temporal lobe epilepsy. Here, we present, illustrate, and discuss important early studies on AHS between 1825 and the turn of the century.