Temporal lobe surgery did not begin with one operation, one surgeon or one institution.
It emerged through a sequence of changes: clinical recognition that some seizures arose from the temporal lobe, the arrival of EEG, attempts to localise abnormal electrical activity, cortical stimulation during surgery and the gradual realisation that disabling focal epilepsy could sometimes be treated even when there was no obvious tumour or surface scar to remove.
That transition took place mainly during the 1930s, 1940s and early 1950s.
It involved two major centres in particular: the Montreal Neurological Institute under Wilder Penfield and Herbert Jasper, and the University of Illinois programme led by Percival Bailey and Frederic Gibbs.
This page follows that transition. It is deliberately separate from the site’s Montreal procedure page, which focuses on Penfield’s broader cortical mapping work, and from the earlier Victor Horsley page, which covers the nineteenth-century beginning of localisation-guided surgery.
Why the temporal lobe became important
Nineteenth-century neurologists had already described seizures involving fear, altered awareness, unusual smells or tastes, automatisms, memory-like experiences and what Hughlings Jackson called dreamy states.
These attacks did not resemble the classic motor Jacksonian march.
They suggested that focal seizures could arise from brain regions involved in memory, emotion, perception and behaviour.
By the early twentieth century, clinicians increasingly connected many of these phenomena with the temporal lobe, particularly its medial and anterior regions.
Psychomotor epilepsy
In the 1930s, Frederic Gibbs, William Lennox and colleagues used the term psychomotor epilepsy for a group of seizures involving mental, emotional, autonomic and motor phenomena.
The term is now obsolete, but historically it was crucial.
It gave clinicians a framework for seizures that could involve staring, automatisms, experiential symptoms, behavioural change and impaired responsiveness without beginning as a major convulsion.
EEG then strengthened the idea that many of these attacks had a focal temporal origin.
EEG changes surgical selection
Before EEG, epilepsy surgery generally depended on visible or strongly suspected structural lesions.
A surgeon might remove a tumour, scar or damaged cortical area that appeared to correspond with the seizure pattern.
EEG created a new possibility.
If recurrent epileptiform discharges repeatedly appeared over the same temporal region, perhaps surgery could be considered even when no obvious mass lesion was present.
This was a major conceptual change: from lesion-directed surgery toward electrophysiologically directed surgery.
Montreal in the 1930s and 1940s
Wilder Penfield had trained with Otfrid Foerster in Breslau and brought awake cortical stimulation and careful functional mapping into his epilepsy surgery programme.
At the Montreal Neurological Institute, founded in 1934, Penfield and colleagues operated on patients with focal epilepsy using clinical semiology, neurological examination, stimulation mapping and later EEG.
Herbert Jasper joined the Montreal programme in the late 1930s and helped integrate electroencephalography into surgical evaluation.
That reduced the number of operations in which no convincing abnormal region could be found and strengthened the relationship between clinical seizure pattern and electrical localisation.
Penfield was initially cautious about non-lesional temporal surgery
Penfield’s early temporal lobe operations were not simply routine removals of apparently normal temporal tissue.
Historical reviews note that he remained cautious when no structural lesion was visible.
Many early operations were still directed toward tumours, scars or other identifiable pathology.
This caution distinguished the Montreal approach from the more aggressive EEG-directed non-lesional resections that would soon be attempted in Chicago.
The Chicago programme: Gibbs and Bailey
Frederic Gibbs moved to the University of Illinois in Chicago in 1944.
There he established an epilepsy programme and worked with neurosurgeon Percival Bailey.
Gibbs had become convinced that recurrent temporal EEG abnormalities in people with disabling psychomotor seizures identified a surgically treatable focus even when no tumour could be demonstrated.
He persuaded Bailey to operate on selected patients on the basis of electroclinical localisation.
1947: non-lesional temporal lobe excisions
Modern historical reviews describe 1947 as a key date.
Bailey and Gibbs performed some of the first temporal lobe resections for medically refractory psychomotor epilepsy in patients without an obvious structural lesion, using EEG to guide localisation.
This was a decisive change in epilepsy surgery.
The operation was no longer simply removing a visible tumour that happened to cause seizures.
The seizure disorder itself — localised through clinical and electrical evidence — had become the surgical target.
By 1948, anterior temporal lobectomy became their preferred procedure
Gibbs and colleagues had studied large numbers of EEGs from patients with psychomotor seizures and found that many showed abnormalities maximal over the anterior temporal region.
By 1948, Bailey’s programme had moved toward anterior temporal lobectomy as its preferred operation for carefully selected patients.
The procedure removed anterior lateral temporal cortex but initially spared important medial temporal structures.
Why Bailey spared the hippocampus and hippocampal gyrus
This decision was deliberate.
Bailey knew of the behavioural syndrome described by Heinrich Klüver and Paul Bucy after extensive bilateral temporal damage in monkeys.
Because the hippocampal region was thought to contribute to those behavioural changes, Bailey avoided removing the hippocampus and hippocampal gyrus in an attempt to reduce postoperative neurobehavioural risk.
That choice made sense from the knowledge available at the time.
It may also have limited seizure control because later evidence showed that the mesial temporal structures are often central to temporal lobe epilepsy.
The Bailey–Gibbs 1951 report
In 1951, Percival Bailey and Frederic Gibbs published The Surgical Treatment of Psychomotor Epilepsy in JAMA.
The paper became one of the classic early reports of EEG-directed temporal lobe surgery. Historical reviews identify Bailey as the first surgeon to systematically attempt temporal lobectomies for psychomotor seizures and one of the first to use electrocorticography for intraoperative localisation.
The significance of the work lay less in one individual operation than in the principle it established: medically refractory temporal epilepsy could itself be a surgical indication.
Meanwhile, Montreal was developing a parallel approach
Penfield and Herman Flanigin published a major series on temporal lobe seizure surgery in 1950.
Their analysis covered 68 patients operated on during a ten-year period ending in April 1949, with another 30 patients operated on in the following year.
Penfield explicitly acknowledged Herbert Jasper’s contribution and emphasised that understanding of focal temporal seizures had made a new field of surgical therapy possible.
Montreal therefore played a parallel and overlapping role rather than simply following Chicago.
The importance of electrocorticography
Scalp EEG had limitations.
Temporal electrical activity could be difficult to localise precisely, especially when the epileptogenic region was deep or mesial.
Electrocorticography — recording directly from the exposed cortical surface during surgery — allowed surgeons and neurophysiologists to look for abnormal discharges much closer to their source.
This became an important part of early temporal lobe surgery programmes.
It also reinforced the idea that the tissue generating seizures might extend beyond an obvious structural lesion.
Electrical stimulation had two roles
Cortical stimulation could help identify eloquent cortex that should be preserved.
It could also reproduce phenomena resembling a patient’s habitual seizure aura or experiential symptoms.
In Montreal, stimulation of temporal structures helped connect déjà vu-like experiences, memory phenomena, fear and other experiential symptoms with the temporal lobe.
The surgeon was therefore using stimulation both to protect function and to test localisation.
Lesion versus epileptogenic cortex
Another concept was changing.
Jackson had suggested that seizures might arise not from the centre of a destroyed lesion but from the irritated or partially damaged tissue around it.
Penfield and colleagues later argued similarly that removing only the visible lesion might be insufficient if surrounding cortex remained epileptogenic.
This helped move epilepsy surgery away from simple lesion excision toward the concept of removing an epileptogenic zone.
The medial temporal lobe becomes central
Early lateral temporal resections were not always sufficient.
During the late 1940s and early 1950s, increasing clinical, EEG and pathological evidence pointed toward the importance of deeper medial temporal structures, particularly the hippocampus and amygdala.
This was a major conceptual shift.
The epileptogenic region might not be visible on the cortical surface at all.
Penfield and Flanigin’s 1950 series
Penfield and Flanigin’s 1950 report described the results of surgery for temporal lobe seizures over the previous decade.
The authors emphasised that many cases once considered ‘idiopathic’ could now be understood as focal cerebral attacks.
This sentence captures the historical transition clearly.
Temporal lobe surgery was helping redefine the epilepsy itself.
Penfield and Baldwin: subtotal temporal lobectomy
In 1952, Wilder Penfield and Maitland Baldwin published a detailed description of the technique of subtotal temporal lobectomy.
The operation included more extensive removal of temporal tissue and increasingly incorporated mesial temporal structures.
This represented a further step beyond the earlier, more limited anterior temporal resections.
Falconer and the en bloc anterior temporal resection
In London, neurosurgeon Murray Falconer further developed temporal lobe surgery during the early 1950s.
Historical reviews credit Falconer with introducing an en bloc anterior temporal lobe resection in 1953 and with emphasising pathological examination of the removed specimen.
Removing the specimen in one piece made detailed neuropathological study easier.
This helped connect surgical outcome with specific abnormalities in the hippocampus and temporal lobe.
From ‘mesial temporal sclerosis’ to hippocampal sclerosis
Falconer’s programme contributed to growing recognition of sclerosis in the medial temporal structures as an important pathological substrate of temporal lobe epilepsy.
The underlying pathological change had been described earlier — Wilhelm Sommer had reported characteristic hippocampal neuronal loss in the nineteenth century — but surgery now made it possible to connect such pathology directly with clinical epilepsy and postoperative outcome.
The terminology later stabilised around hippocampal sclerosis.
This was no longer simply ‘removing a scar’
The temporal lobectomy era changed the logic of epilepsy surgery.
Horsley’s nineteenth-century operations had largely targeted visible lesions or scars identified through clinical localisation.
By the mid-twentieth century, surgeons were increasingly prepared to remove cortex because EEG, semiology and stimulation indicated that it was epileptogenic.
That is a fundamentally different type of surgical reasoning.
The price of more effective resections
More extensive temporal resections created new neurological risks.
The temporal lobe is central to language and memory.
Removing tissue from the dominant temporal lobe could impair verbal learning and naming.
Removing medial temporal structures could affect memory.
These problems gradually forced epilepsy surgery to become not just a localisation discipline but also a neuropsychological one.
Brenda Milner and the rise of surgical neuropsychology
The Montreal programme became particularly important in studying cognitive outcomes.
Brenda Milner’s work on patients undergoing temporal lobe surgery helped demonstrate that different temporal regions contribute differently to memory and language.
These observations transformed preoperative assessment.
The question was no longer only ‘Can we remove the seizure focus?’
It also became ‘What function might be lost if we do?’
The Wada test enters the story
Juhn Wada developed the intracarotid amobarbital procedure in Japan and introduced it to the Montreal programme in the 1950s.
By temporarily suppressing one cerebral hemisphere, clinicians could assess language dominance and later memory function before temporal lobe surgery.
This was a direct response to the risks created by increasingly effective temporal resections.
Why temporal lobectomy became a model for epilepsy surgery
Temporal lobe epilepsy eventually became one of the clearest examples of surgically treatable focal epilepsy.
That happened because several kinds of evidence could converge:
the seizure semiology;
the scalp EEG;
sometimes intracranial or intraoperative recordings;
neuropsychological findings;
and, later, structural imaging.
Temporal lobectomy therefore became a model for multidisciplinary epilepsy surgery.
The early results were encouraging but imperfect
Penfield and Flanigin’s 1950 series reported substantial improvement in many patients, and later follow-up continued to support the effectiveness of temporal lobe surgery.
But early outcome reporting did not use today’s standardised seizure-freedom classifications.
Definitions of ‘success’, follow-up duration and patient selection differed across centres.
Historical percentages should therefore not be compared directly with modern surgical outcome statistics.
Two centres, two overlapping traditions
The history is sometimes simplified into a competition between Montreal and Chicago.
That is misleading.
Montreal developed awake cortical stimulation, extensive functional mapping, EEG integration and increasingly sophisticated temporal resections.
Chicago pushed particularly strongly toward EEG-directed surgery for non-lesional psychomotor epilepsy.
Both programmes helped establish anterior temporal lobectomy as a serious treatment for drug-resistant temporal lobe epilepsy.
What made these operations historically different
The difference was not simply that surgeons removed part of the temporal lobe.
It was that surgery was now based on an inferred epileptogenic system.
The target might be selected through seizure description, EEG abnormalities, stimulation responses and functional mapping even when no tumour was visible.
That is one of the defining transitions from early neurosurgery to modern epilepsy surgery.
The central historical lesson
The first temporal lobectomies were not one clean ‘first’ operation.
They emerged from several parallel developments.
Penfield’s Montreal programme showed how temporal seizures could be investigated through stimulation, clinical observation and later EEG.
Gibbs and Bailey demonstrated that non-lesional psychomotor epilepsy could be treated surgically using EEG localisation.
Penfield, Flanigin and Baldwin developed increasingly systematic temporal resections.
Falconer helped connect en bloc temporal surgery with pathological study of the hippocampus and mesial temporal structures.
Together, these developments changed the purpose of epilepsy surgery.
The surgeon was no longer only removing a visible lesion that happened to cause seizures.
The seizure-generating region itself had become the target.
Sources and further reading
Penfield W, Flanigin H. Surgical Therapy of Temporal Lobe Seizures. Archives of Neurology & Psychiatry. 1950;64:491–500.
Penfield W, Flanigin H. Surgical therapy of temporal lobe seizures. 1950. PubMed PMID 14770593.
Loring DW. History of Neuropsychology Through Epilepsy Eyes. Archives of Clinical Neuropsychology. 2010.
Vannemreddy P et al. Psychomotor seizures, Penfield, Gibbs, Bailey and the development of anterior temporal lobectomy: a historical vignette. Annals of Indian Academy of Neurology. 2010.
Vannemreddy P, Stone JL, Slavin KV. Frederic Gibbs and his contributions to epilepsy surgery and electroencephalography. Neurosurgical Focus. 2011.
Penfield W, Paine K. Results of Surgical Therapy for Focal Epileptic Seizures. Canadian Medical Association Journal. 1955.
Diverse perspectives on developments in epilepsy surgery. Seizure. 2011.
Magiorkinis E et al. Highlights in the History of Epilepsy: The Last 200 Years. Epilepsy Research and Treatment. 2014.
Historical evidence checked: September 2026.