“Neurologists should push their investigation into the neurologic mechanism associated with consciousness and should inquire closely into the localization of that mechanism without apology… To make such an inquiry is to ask a very old question, as is shown by the following quotation from the Book of Job:
Surely there is a vein for the silver
And a place for the gold where they find it
But where shall the wisdom be found?
And where is place of understanding?”
– Wilder Penfield (1938)
A Framework for Brain Surgery
Wilder Penfield and the Rise of Modern Neurosurgery
By Marzieh Ghiasi (Apr 2010)
n July 29th, 1935, 667 neurologists and neurosurgeons from forty-two countries gathered in University College in London, England for the second International Neurological Congress. The conference, which lasted for five days, featured some 300 manuscripts. One of these papers, entitled Epilepsy and Surgical Therapy, was printed by the neurosurgeon Wilder Penfield from Canada. Penfield was keenly interested in developing a functional map of the human brain in order to better understand and provide treatment options for various brain disorders. Throughout his career, he built a reputation for developing new investigative and curative neurosurgical procedures.
Penfield’s thirty-five page manuscript, hereafter known as the 1936 paper as it was published several months after the conference, can be divided in two parts. In the first seven pages of the work, Penfield lays out a map of the brain, setting the ground and criteria by which epileptic foci, aberrations in the brain leading to seizures, can be localized and studied. In the second twenty-eight pages of the paper, he describes different categories of epilepsies based on their phenomenology and etiology, and proposes neurosurgical treatment where possible.
I contend that Penfield’s purpose in this paper is to (1) build on and synthesizing the traditional body of the field, (2) use the scientific method to collect and interpret data, (3) introduce a curative innovation to the field and (4) establish a cultural and practical framework within which neurosurgeons of the future can operate. He organizes arguments in the paper based on hypothesizing, scientific observation, experimentation, and deductive reasoning. These aspects of the paper would have made it particularly compelling to the audience in the International Neurological Congress and particularly important in context of the history of neurosurgery.
Building on Traditions
The second International Neurological congress was held on the centennial birthday of John Hughlings Jackson (1835-1911). Hughlings Jackson was a prominent English neurologist who studied neurological disorders such as epilepsy, seeking to understand them physiologically. One of his major contributions was in developing cerebral localization theory which holds that different areas of the brain are distinctly specialized for different functions. Hughlings Jackson’s lucid and comprehensive accounts and case studies influenced many neurologists and neurosurgeons in the latter part of the nineteenth century. It is no surprise then that Penfield’s 1936 paper references him in several occasions.
The earliest precursor to Penfield’s work, however, can be found early nineteenth century, before the advent of cerebral localization theory. At the time phrenology, a theory which held that bumps in the human skull could be associated to people’s personalities, had been very popular. By mid-nineteenth century, however, phrenology was widely discredited as a pseudoscience leading to a general disinclination towards localization theories. Nevertheless, in 1861, a French neurologist Pierre Paul Broca (1824-1880) was able to associate aphasia, a disorder in which speech is severely impaired, with lesions in the brain. Hughlings Jackson, following Broca’s idea, hypothesized that during epileptic episodes, a form of "discharging lesion" prevented parts of the brain from performing normally, and the output was observed in seizures. By carefully noting seizure patterns in his patients, and doing post-mortem studies where he observed damaged tissues in the brain, he concluded that behavioral outputs could be represented and mapped onto the tissues of the brain.
By 1879, the work of Hughlings Jackson and contemporaries such as Romberg in Germany, Dejerine, Babinski, and Charcot in France led to the establishment of cerebral localization theory, which along with antiseptics and anaesthesia ended the pre-modern era in neurosurgery. Throughout his 1936 paper, Penfield describes the work and experiments of these individuals in order to provide a theoretical framework on which he bases his studies. For example, in pages 463-464, when describing a vascular phenomenon observed in epileptic patients, Penfield refers back to papers from late nineteenth century including one from 1866 by Czemark that reported similar phenomena.
Medical historians consider the era between 1879-1919 a transition period. Here the success of individuals such as Harvey Williams Cushing (1869-1939), who is considered the father of modern neurosurgery, allowed the practice to be recognized as a separate profession from neurology or general surgery. By the third era, beginning in 1920, neurosurgery had been established as a distinct profession— but was now emerging as a scientific discipline with technical and cultural doctrines of its own. When Wilder Penfield began his first surgical apprenticeship at New York in 1921, he was in the first generation of surgeons to be trained in the modern period of neurosurgery.
Penfield was born in 1891 in Spokane, Washington to a university-educated, middle-class family. He enrolled in Princeton University with no intention to study medicine like his father. However by 1915, he received a Rhodes Scholarship an decided to pursue medicine in Oxford University. In his time in Oxford, Penfield found a mentor in prominent physician Sir William Osler (1849-1919), whom he later lionized as an inspiration, and a “hero” in the field of medicine. Osler was well-known as a rigorous adherent of the scientific method in medicine, and would certainly have had a deep influence on Penfield’s thinking and approach to neurosurgery.
Another major influence in Penfield’s thinking was Sir Gordon Holmes (1876-1965), a neuroanatomist who Penfield followed in clinical rounds. While observing Holmes’ work, Penfield became very interested in his epileptic patients. However, he later wrote that he was dismayed by the lack of treatment options available for these patients.
“I would never be content, I thought, to be such a neurological surgeon. I must learn what was known about two subjects: pathological lesions, and neuroanatomy. Finally, someday, I would study two other things: the mystery of epilepsy, and how the human brain does what it does.”
Having completed his studies in Oxford, and completing his surgical apprenticeship in New York, in 1928 Penfield received an invitation to work in Montreal as the city’s first neurosurgeon. Feeling that he would have more room to grow outside New York, where many patients turned to more experienced surgeons, he accepted the offer.
A Scientific Discipline
As recounted in a 1935 letter to the Journal of the American Medical Association, the second International Neurological Congress featured a special meeting in commemoration of Hughlings Jackson. The meeting was headlined by German neurosurgeon Otfrid Foerster (1873-1941) who was awarded the Hughlings Jackson Lectureship, the highest honor in neurology from the British Royal Society of Medicine
Foerster established Germany’s first Department of Neurology in 1911, at the onset of the First World War, and became well-known for his successful operations on gunshot wounds of the brain. In 1928, Penfield who had just accepted to move to Montreal was struggling with a problem. One year earlier he had written a paper describing the histology of scarring in brain tissue. In it he hypothesized that scars formed from traumatic injuries could be “the starting point for the nervous discharge resulting in Jacksonian epilepsy”, and suggested that surgery would be an appropriate treatment for epilepsy.
However, he did not know whether scarring from the surgical interventions he proposed led to better or worse outcomes for patients than scarring from trauma. In a chance conversation, he found out about Foerster’s work with gunshot wounds, many of which caused epilepsy. Penfield became convinced that Foerster might have an answer for him. He contacted Foerster promptly, asking to visit his clinic in Germany as a graduate student for six months, after which he would assume his position at McGill University.
During his time in Germany, which he described as “one of the greatest moments in [his] life”, Penfield studied many preserved scar tissue sections from Foerster’s surgeries. These studies confirmed to him that surgical removals led to far less scarring and potential for future seizures than wounds. This established a scientific basis on which he could conduct future surgeries, including those in his 1936 paper.
Perhaps more important was Penfield’s chance to see Foerster in surgery. Foerster used two innovative techniques which Penfield adapted into his own work, and used extensively in his 1936 paper. Foerster operated on conscious patients under local anaesthesia. He also stimulated the brain during surgery with electric probes, based on work by Hans Berger in 1924 establishing that brain activity was tranduced by electrical waves and could be recorded using electroencephalography (EEG). This allowed him to receive a behavioral readout while manipulating the brain, in order to understand what was being manipulated. In his 1936 paper, Penfield acknowledges Foerster’s influence noting, “I began to operate on epileptogenic cicatrices, following the example of Otfried Foerster, in 1928, and my indebtedness to him is obvious.”
After returning to Montreal in September of 1928, Penfield began his work with two directives in mind. The first, continuing his own scientific investigation into curative surgical treatments for epilepsy. The second, creating an institute for scientific research in neurology and neurosurgery.
Foerster and Penfield published a study in 1930 which can be considered the conceptual predecessor to Penfield’s 1936 paper. In this paper they outlined the structural basis of traumatic epilepsy using tissue studies. They also detailed twelve case studies in which brain lesions had been excised, describing their anatomical pathologies and operation outcomes. Penfield considered his work with Foerster as one where he “worked out the story of healing and scarring in the human brain.” His early work, then, had established a scientific basis for his future inquiries.
From 1930 to 1935, Penfield published over a dozen papers, some of which concerned classification of different types of epilepsy based on localization and appropriate surgical treatments. Although Penfield’s 1936 paper was not a review in that it presented new data; the organization and length of the work suggests that it was a synthesis of his ideas and papers in early 1930s period. Also it is notable that the paper departed in structure from Penfield’s earlier scientific papers, providing remarks on the field of neurosurgery.
By the time when Penfield presented his paper in the second International Neurological Congress, his surgical treatment of epilepsy had become known in surgical circles as the Montreal Method. Despite enthusiasm over the possibility of a cure to epilepsy, Penfield’s attempt to localize epilepsy-inducing foci in the brain, and the radical and invasive nature of his procedure led to mixed reactions among his peers. In his 1936 paper, which draws from earlier works, Penfield defends his procedure and counters criticisms by presenting his data using the scientific method.
The first step to the scientific method of inquiry is forming a hypothesis. Penfield not only outlines his own hypotheses for the procedures in the paper, but a working guide on how to form hypotheses for other surgeons. He begins with a preliminary study and within it describes the concept of epileptic foci in the brain, as developed in his earlier paper with Foerster. He describes four factors that a neurosurgeon must consider when conducting a surgery: (1) the epileptic attack pattern (2) the neurological signs (3) brain recordings (4) responses to direct stimulation of brain tissue. These factors are used to form the hypotheses on which surgical approaches later described in the paper are based.
The second step to the scientific method of inquiry is making collecting observations and evidence to support the hypothesis. By early twentieth century, the inclusion of pathological anatomy in the medical curriculum by individuals such as Sir William Osler had ensured that it assumed a central role in modern medicine. Indeed, Penfield’s work in Oxford with both Osler and neuroanatomist Holmes gave him a strong grounding in pathological anatomy. His later work with Foerster was also focused on examining pathological anatomy and histology. In his 1936 paper, he describes the anatomical pathologies thought to be involved in epilepsy. As an example, in page 460 he gives a detailed anatomical description of blood vessels in the brain as well as the surgical procedures performed on these vessels.
Penfield also provides extensive descriptions, photographs and diagrams of anatomical pathologies, such as scarring, that he observed in brain tissues of epileptic patients. The pictures of brain tissue are labeled on site with small numbered tags—as can be seen in figure 6—used to “indicate areas from which movement and sensation in the face and in the mouth were obtained”. These types of pictures provide a testament to the precision and accuracy of the surgeon’s work. Penfield also includes before and after pictures of tissues that have undergone the scar-excision procedure. These pictures are evidence of the phenomena that Penfield describes, and also evidence of the results of his procedure.
The third step in the scientific method of inquiry is experimentation to test a given hypothesis. Like his predecessor, Hughlings-Jackson, Penfield provides in his 1936 paper detailed descriptions of behaviors and sensations observed in patients as readouts of events in the epileptic brain. However, advances in the field also allow Penfield to include behavioral descriptions that are readouts of his experiments with electric stimulation of the brain. For example, he describes stimulating an area of the brain and the visual and auditory hallucinations that result from this, thereby deducing that this area must be responsible for somatosensation. Penfield is also able to induce epileptic attacks, which he recognizes as an innovation that allows neurosurgeons to localize epileptic foci to where there are no obvious anatomical abnormalities.
The fourth step in the scientific method is forming a conclusion based on evidence and recognizing the limitations of the study. In his case studies, Penfield correlates observations, including recoded patterns of attack and anatomical pathologies, with experiment, using electrical exploration, to form an extremely detailed localization of epileptic foci. He is well-aware of the limitations of his procedure and clearly delineates the conditions under which it can be done successfully. He acknowledges that his procedure cannot be hailed as a cure to epilepsy; as for instance, there are certain patterns of attack that he has not been able to reproduce. When outlining his conclusions, he also provides alternative conclusions—proving that his own conclusions are drawn in consideration of multiple points of view.
Penfield is also determined in his 1936 paper to counter what he perceives to be inaccuracies in the field. He uses evidence from his study to refute other studies, noting for instance in one part of the paper, “…at the initiation of an attack I have never observed the widespread shrinking of the brain reported by Foerster.” He further outlines cases where surgical procedures are not justified based on evidence from his case studies. For example, he describes conducting a surgical procedure thought to affect epilepsy by reducing pressure in the brain, and provides evidence from his own patients that the protocol does not to a level that can justify conducting it.
In this paper, Penfield also addresses criticisms targeted at his surgical procedure at length. As discussed previously, phrenology was discredited with the rise of modern neurology, and along with it localization theories of the brain also met extensive criticism. Evidently these criticisms persisted into the 1930s as Penfield notes in his paper that his work is not a new kind of phrenology. He emphasizes that localization in brain tissue does not confine a function to a single area. Rather, it suggests that a particular area "forms an essential link in a mechanism that may well involve distant tracts and connections".
At the time, one of the main criticisms of Penfield’s procedure was that the removal of brain tissues would be risky and induce cognitive defects in a previously normal individual. In a 1930 paper, The Radical Treatment of Traumatic Epilepsy and its Rationale, Penfield outlines some of the procedural concerns, assuring his peers that “careful study with modern scientific methods” as well as safeguards provided with electrical probing would ensure that only damaged tissue would be removed. He re-emphasizes this point throughout the 1936 paper.
Another criticism of Penfield’s earlier papers related back to his own concerns when meeting Foerster. As described, he was concerned about the outcomes, in the form of potential scarring and complications, from invasive surgery of the brain. Although his concerns were relieved following his work with Foerster, and the surgical protocol justified at length in his 1930 publications, some of his peers remained skeptical of outcomes for patients. To address these concerns, in many of his papers, Penfield examined patients for cognitive function months after large amounts of tissue had been removed. In his 1936 paper he addresses these concerns by compiling extensive follow-ups on patients.
“My results (table 2) are as follows: After radical excision… 46 per cent of patients have remained attack-free and 32 per cent are markedly improved.”
Penfield’s 1936 paper outlines and reinforces modern paradigms and expectations in the field of neurosurgery in several ways. He strongly focuses on the scientific method and empiricism as the only way to approach modern neurosurgery. This was accomplished through establishing hypothesis, and doing careful experimental study before forming any conclusions. To emphasize the importance of forming hypotheses, Penfield uses a quote from a contemporary neurosurgeon, describing a surgeon operating without a hypothesis as one who “places himself on a level with the practitioner of the stone age.”
Although in his paper Penfield establishes a broad framework for understanding and operating on different types of epileptic lesions, he emphasizes that one cannot generalize from one anomaly to another. In particular he set limits on practitioners in that surgery must only be done after physiological and pathological dynamics of the condition have been fully studied. He emphasizes the importance of taking patient-histories, similar to practitioners like Hughlings-Jackson, and being in touch with patients He also encourages neurosurgeons to engage in careful and considerate practice. Specifically he notes that neurosurgeons should be competent in neuropathology, and should be able to recognize the appropriate response to a given form of epilepsy. He also stresses exercising extreme caution when undertaking surgery, describing situations where a surgical procedure can be “as ill-advised… as the removal of a normal colon or adrenal body.”
The work of a surgeon at the cusp of a transformation in neurosurgery, Penfield’s 1936 manuscript can be considered as a reflection of broad trends in science and medicine at the turn of the century. When Penfield arrived in Montreal to begin his professional life, he was quite aware and perceptive of the changes taking place in his discipline. There were two themes in particular that interested him: The first was specialization and professionalization of neurosurgery as a field. In a brief address he published in 1928 in the Canadian Medical Association Journal he wrote,
“Thanks to peculiar conditions in American professional and university life it has been possible for an ever increasing group of men to confine their activity to neurosurgery. The result has been a rapid expansion of this speciality.” 
The second was the potential of neurosurgery as a curative field, on which he wrote,
"The field of neurosurgery, both now and in the future, should not be confined to tumours of the nervous system… On the contrary, it should include the prevention and the cure of traumatic epilepsy, control of cardiovascular pain and of intractable pain of all types…"
These two interests are evident in Penfield’s 1936 paper where he builds on the traditional body of field, and introduces new data and curative innovations to field. But Penfield does not seek to simply introduce new methods in a neurosurgery. Rather, Penfield encourages neurosurgeons to assess his work critically and adapt it to their practice after careful consideration. He also calls for his peers, neurosurgeons of a new generation, to incorporate the scientific method as a way of problem-solving and practice in neurosurgery.
 Lewis, J. (1983). Something Hidden: a biography of Wilder Penfield. Halifax, N.S.: Goodread Biographies. p. 202.
 Reynolds, E. H. (2005). The John Hughlings Jackson 1935 Centenary Congress Medal. Journal of Neurology, Neurosurgery & Psychiatry, 76(6), 858-859.
 Walker, A. E. (1951). A history of neurological surgery. Mansfield Centre, Conn.: Martino Pub. p. 20.
 Penfield, W. (1936). Epilepsy and surgical therapy. Archives of Neurology and Psychiatry, 36(3), 449-484. p. 450.
 Greenblatt, S. H., Dagi, T. F., & Epstein, M. H. (1997). A history of neurosurgery : in its scientific and professional contexts. Park Ridge, Ill.: American Association of Neurological Surgeons. p. 137.
 Ibid, p. 142.
 Walker, 1951, p. 20.
 Penfield, 1936, p. 464.
 Greenblatt et al., 1997, p. 4.
 Lewis, 1983, p. 84.
 Ibid, p. 3.
 Ibid, p. 27.
 Ibid, p. 49.
 Penfield, W. (1949). Hero Worship. Archives of Internal Medicine, 84(1), 104-109.
 Penfield, W. (1977). No Man Alone. Toronto, O.N.: Little, Brown and Company.p. 48.
 Lewis, 1983. p. 105.
 Foreign Letters. (1935). Journal of the American Medical Association, 105(10), 809-814.
 Walker, 1951, p. 287.
 Ibid, p. 286.
 Penfield, W. (1927). The mechanism of cicatricial contraction in the brain. Brain, 50, 499-517. p. 510.
 Penfield, 1977, p. 158.
 Ibid, p. 160.
 Ibid, p. 166.
 Walker, 1951, p. 296.
 Penfield, 1936, p. 477.
 Penfield, 1977, p. 233.
 Ibid, p. 222.
 Foerster, O., & Penfield, W. (1930). The structural basis of traumatic epilepsy and results of radical operation. Brain, 53, 99-119.
 Penfield, 1977, p. 167.
 Lewis, 1983, p. 127.
 Penfield, 1936, p. 450.
 Ibid, p. 461.
 Ibid, p. 472.
 Ibid, p. 453.
 Ibid, p. 452.
 Ibid, p. 451.
 Ibid, p. 454.
 Ibid, p. 458.
 Ibid, 1936, p. 465.
 Penfield, 1936, p. 451.
 Lewis, 1983, p. 127.
 Penfield, W. (1930). The radical treatment of traumatic epilepsy and its rationale. Canadian Medical Association Journal, 23, 189-197.
 Penfield, 1936, p. 482.
 Ibid, p. 450.
 Ibid, p. 449.
 Ibid, p. 451.
 Ibid, p. 450.
 Penfield, W. (1928). An address on the field of neurosurgery. Canadian Medical Association Journal, 19, 654-655.