The vascular hypothesis held that posttraumatic epilepsy results from reflex vasoconstriction of cortical arteries around a cerebral scar. Penfield’s initial support and eventual refutation of the vascular hypothesis is the subject of this paper, which is based on a review of his clinical charts, operative and electrocorticographic reports, and brain maps held in the Montreal Neurological Institute archives. Penfield and his collaborators discovered that posttraumatic cortical scars are composed of astro-glial fibers, collagen fibrils, and a neo-vascular plexus that anastomoses with the surrounding cortical arteries. He hypothesized that the contracting scar applied traction to these arteries, which caused epileptic seizures. This was supported by his observations that cortical arteries constrict during an epileptic seizure. Penfield’s subsequent investigations led to the discovery that parasympathetic nerves innervate the intracranial arteries, that experimental vasospasm can produce cortical infarction, and that cerebral blood flow (CBF) is coupled to cerebral metabolism. In fact, Penfield found that CBF increases in the epileptogenic zone around a cortical scar, contrary to what the hypothesis had predicted. Despite this, Penfield’s investigations shed new light on the dynamics of the cerebral circulation that were not fully understood until decades later.
Wilder Penfield (1891–1976) is widely regarded as a dominant figure in 20th century neurobiology for his singular contributions to the structure-function relationship of the brain, his discovery of the language function of the supplementary motor area, the discovery (with Herbert Jasper and Brenda Milner) of the anatomy of recall, and his pioneering work in the surgical treatment of focal epilepsy. But another of his significant discoveries has escaped notice: the recognition that focal microgyria can generate epileptic seizures, and that these can be treated surgically. Penfield discussed the case of the patient through which this discovery was made during his Shattuck Lecture to the Massachusetts Medical Society in 1939. As Penfield gave only a fragmentary account of this case, the patient's chart was retrieved from the Montreal Neurological Institute archives, and his operative note and brain map, intraoperative photographs, and the histopathological and cytological examinations of the resected specimen were reviewed. Based on these primary sources, this paper provides a complete, detailed account of the first case in which microgyria was recognized as a cause of focal epilepsy, which was successfully treated surgically.
Neurosurgery is predicated on the knowledge of the structure-function relationship of the brain. When the topic is broached in its historiography, it begins with Fritch and Hitzig's report on the localization of motor function in the cortex of the dog and skips rapidly to Wilder Penfield's homunculus. In that gap are found the origins of modern neurosurgery in 3 papers published by Jean-Martin Charcot and Albert Pitres between 1877 and 1879 in which they describe the somatotopic organization of the human motor cortex and draw the first human brain map. Their findings, obtained through the clinicopathological method, gave relevance to David Ferrier's observations in animals. Their work was extensively cited, and their illustrations reproduced by Ferrier in his landmark lecture to the Royal College of Physicians in 1878. It was known to William Macewen, who used localization to guide him in resecting intracranial mass lesions, and to William Osler and John Hughlings Jackson, who were early advocates of intracranial surgery. This paper describes Charcot and Pitres' discovery of the cortical origin of human voluntary movement and its somatotopic organization, and their influence on 19th-century intracranial surgery. It fills a gap in the historiography of cerebral localization and neurosurgery.
The localization of articulate language (speech) to the posterior third of the third left frontal convolution—Broca’s area—did not occur to Broca as he reported the case of his first aphasic patient in 1861. Initially Broca localized articulate language to both frontal lobes, a position that he maintained for 4 years after publishing his first case. In the interval, the Academy of Medicine in Paris had received a copy of a paper authored in 1836 by Marc Dax, in which Dax claimed that the ability to speak resides within the left hemisphere alone. The Academy of Medicine convened in the spring of 1865 to adjudicate the issue. All of the distinguished speakers argued against Dax’s contention by citing the prevailing paradigm, that bilaterally symmetrical organs, such as the eyes and ears, and the hemispheres of the brain, must perform the same function. The lone dissenting voice was that of Jules Baillarger, the discoverer of the laminar organization of the cerebral cortex, whose argument in favor of what he called “Dax’s law” was so lucid that it carried the day. During his address to the Academy, Baillarger not only supported left-hemisphere dominance for speech, but for the first time described two forms of aphasia, fluent and nonfluent, now referred to as Wernicke’s and Broca’s aphasias, respectively, as well as the ability of aphasics to speak during emotional outbursts, to which we now refer as Baillarger-Jackson aphasia. It was 9 days after Baillarger’s address that Broca, for the first time, unequivocally localized speech to the left frontal lobe.
This paper is based on the author’s reading of Dax’s and Broca’s original texts and of the texts read before the Academy of Medicine meeting held at the National Library of France between April 4, 1865, and June 13, 1865. From these primary sources it is concluded that the Academy of Medicine’s debate was the last serious challenge to left-hemisphere dominance for speech and to the localization of articulate language to the left frontal lobe—and that Jules Baillarger played a pivotal role in what was a defining moment in neurobiology.
Harvey Cushing and Wilder Penfield enjoyed a unique professional and personal relationship. Shortly before his retirement from Harvard University in 1933, Cushing sent Penfield 8 sketches that he drew in 1902 and 1903 while he was at Johns Hopkins Hospital. The first series of 3 sketches illustrate the relationship between a cortical hemorrhagic lesion and the motor strip in a patient with focal motor seizures. The second series also comprises 3 sketches. These depict the operative findings in a patient in whom Cushing had electrically stimulated the precentral gyrus, before resecting the cortex subserving motility of the upper extremity to control painful dyskinetic movements. The third series consists of 2 sketches that illustrate the results of stimulation of the motor strip as an aid in the safe resection of an epileptogenic focus in a patient with Jacksonian seizures. These sketches are the subjects of this paper. They add to the relatively sparse record of Cushing’s activities in cortical stimulation and in the treatment of functional disorders.
Eric W. Peterson, Roger Searle, Francis F. Mandy, and Richard Leblanc
✓ Topical dibutyryl cyclic adenosine monophosphate (AMP) was used to reverse experimental cerebral vasospasm of the basilar artery in the cat. The combination of dibutyryl cyclic AMP and theophylline caused prolonged dilatation of the basilar artery. Dibutyryl cyclic AMP seems to be specific as a topical vasodilator, which may be useful in the postoperative management of subarachnoid hemorrhage.
Richard Leblanc and Ernst Meyer
✓ A case is presented which represents the first instance of the use of functional positron emission tomography (PET) scanning to precisely localize a structural brain lesion to the precentral gyrus, and the first validation of functional PET scanning by intraoperative cortical mapping. The lesion was a 3-cm arteriovenous malformation (AVM) that had produced a generalized seizure in an otherwise asymptomatic young woman. A first, resting H2 15O PET scan identified the AVM. A second PET scan, performed during vibrotactile stimulation of the contralateral hand, identified the somatosensory area of the hand region and localized the AVM to that part of the precentral gyrus immediately in front of it. This relationship and localization were confirmed by cortical mapping at the time of craniotomy under local anesthesia. Functional PET scanning may prove to be useful to localize cortical lesions precisely and to help in determining preoperatively the best form of treatment for lesions, especially AVM's, in functionally important cortex.