A student of Theodor Billroth, Eiselsberg served as professor of medicine at Utrecht University and at University of Königsberg before being appointed head of the First Department of Surgery at the University of Vienna. He was one of the founders of neurosurgery, co-founder of the Austrian Cancer Society in 1910, and an honorary member of the Austrian Academy of Sciences. It was his initiative that lead to the creation of the world-first emergency surgery station in Vienna, dramatically increasing the effectiveness of medical intervation after accidents.
He himself died during the early days of World War II in an accident caused by the collision of two trains in the vicinity of St. Valentin, Lower Austria, on October 25, 1939.