Background: Dr. Penfield was a pioneer in neurosurgery and his contribution continues to impact the practice today. Our objective is to analyze the epilepsy surgeries during his career. Methods: Analysis of original operating room books from 1934-1960. Results: He performed 2338 procedures during his career. 601 (26%) epilepsy, 524 (22%) oncology, 441 (19%) general neurosurgery, 379 (16%) functional, 230 (10%) spine, 80 (3%) trauma, 54 (2%) vascular, 29 (1%) nerves.

Epilepsy cases were divided: local vs. general anesthesia and a focal resection or lobectomy. From 1934-1945 he performed 167 procedures, 146 local anesthesia with focal resection. From 1946-1950 223 procedures, introduction of lobectomies with 30. Most right-side procedures under general anesthesia. From 1951-1955 152 procedures, 88 focal resection, 64 lobectomies. From 1956-1960 59 surgeries, similar number of focal resection and lobectomies. Conclusions: To our knowledge this is the most complete and comprehensive account his surgical career. In early years patients were treated through large craniotomies with EEG stimulation to tailor focal resections now known as the “Montreal procedure”. This led to a better understanding of human cortex and the division of the brain functions. During later years, there was a reduction in the number of cases done under local anesthesia and increase in lobectomies.