Paul Ferdinand Schilder was born in Vienna in 1886 and died in New York in 1940. He is nowadays remembered predominantly for his contributions to modern psychiatry and psychotherapy; however, he was also a neurologist and neuroscientist and in particular in his early years, he researched and published on neuropathological topics. This paper focuses on his scientific work during his years in Middle Germany (1909-1914), where he worked with Gabriel Anton in Halle and Paul Flechsig in Leipzig. During those years, he laid the foundations for his definition, clinical classification and differentiation of encephalitis periaxialis diffusa. Today, this inflammatory brain disease is known as Schilder's disease and is of some importance as a rare differential diagnosis of multiple sclerosis (MS), especially in children. Schilder's reflections and findings were based on his scrupulous and detailed analysis of only a few medical histories, which also comprised histological neuropathological examinations, as well as on his extensive and critical review of the relevant literature of the time. His aim was to differentiate encephalitis periaxialis diffusa from brain tumors, MS and Heubner's diffuse sclerosis. Schilder's scientific achievement, made in relatively young years, is still impressive even to the present day due do its thoroughness and accuracy as well as the enormous workload and ambition it required. Even though ambitious, Schilder was always prepared to critically review his own ideas.
Keywords: Encephalitis periaxialis diffusa; First description; History of neurology; Multiple sclerosis; Twentieth century.