Creutzfeldt was habilitated at Kiel in 1920, and in 1925 became "Extraordinarius" of psychiatry and neurology. In 1938 he was appointed professor and director of the university psychiatric and neurological division in Kiel. He helped to recognize a neurodegenerative disease, with Alfons Maria Jakob, Creutzfeldt–Jakob disease in which the brain tissue develops holes and takes on a sponge-like texture. It is now known it is due to a type of infectious protein called a prion. Prions are misfolded proteins which replicate by converting their properly folded counterparts.