Harvey Cushing's paradigmatic contribution to neurosurgery and the evolution of his thoughts about specialization.

The modern era of neurosurgery began in 1879 with the amalgamation of three technologies: anesthesia, antisepsis/asepsis, and cerebral localization. However, when Harvey Cushing (1869-1939) took his first tentative steps toward a neurosurgical career in 1901, the outlook for the field was dismal, because mortality and morbidity rates were horrific. For brain tumors, surgical mortality rates were 30-50%. I will argue that Cushing made intracranial surgery clinically effective, rather than just feasible, by adding a critical fourth technology: knowledge and control of intracranial pressure (ICP). During his Wanderjahr in Europe (1900-1) Cushing came to understand ICP in biophysical terms. At Johns Hopkins, these lessons were quickly translated to acute human traumatic cases (1901-4) and then to tumor patients with raised ICP (1903-5). By 1910, he had accumulated enough tumor cases (180) to have convincing statistics. His mortality rate for tumors was 10-15%. Nonetheless, the successful paradigm was not fully instantiated until a community of practitioners formed a neurosurgical society in 1920. As this process unfolded, Cushing's ideas about specialization also evolved in interesting ways.