The First Case of Invasive EEG Monitoring for the Surgical Treatment of Epilepsy: Historical Significance and Context
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Summary: Purpose: Controversy persists about when EEG became a fundamental tool in the preoperative investigation for epilepsy surgery. We revisit Penfield's first use of invasive EEG monitoring, emphasizing its historical importance for the evolution of epilepsy surgery. Methods: Patients' hospital charts and articles published before 1940 regarding EEG and epilepsy or EEG and cerebral lesions were reviewed to evaluate the historical context of the surgery. Results: In April 1939, Penfield performed trephination over both temporal regions and placed electrodes on the dura, intending to lateralize seizure origin in a patient with bitemporal epilepsy. The patient underwent serial EEGs with this technique. The final report of the recordings from epidural leads was “continued random delta activity in the left temporal region indicating a cortical lesion on this side.” The pneumoencephalogram showed “the presence of diffuse cerebral atrophy, particularly in the left cerebral hemisphere.” Based on these findings, the patient underwent surgery on April 21, revealing a meningocerebral scar in the posterior part of the left temporal lobe. Brain stimulation and electrocorticography delineated the extent of resection, while preserving the speech area. Seizures did not improve. Conclusions: We revisit the first case of epidural EEG monitoring for epilepsy surgery and show that the concept of EEG‐directed surgery was already present at the Montreal Neurological Institute in the late 1930s.Keywords:
Electrocorticography
Anterior temporal lobectomy
Summary: We investigated the relationship between electrocorticography (ECoG), quantitative magnetic resonance imaging (MRI), and surgical outcome in 165 patients with intractable nonlesional temporal lobe epilepsy (NLTLE). A standard mesial temporal resection was performed in all patients. Patients with an operative follow‐up <1 year were excluded from the study. The extent of the lateral temporal neocortex resection (LCR) was guided by ECoG and the side of surgery. The extent of the LCR was not predictive of seizure outcome in patients with or without hippocampal formation atrophy (p > 0.5). Patients undergoing a right anterior temporal lobectomy had a larger LCR (p < 0.000l), but the side of surgery was not of predictive value in determining seizure outcome (p > 0.1). The topography of the acute intracranial spikes did not correlate with operative outcome (p > 0.5) and was independent of hippocampal volumetric studies (p > 0.5). The postexcision ECoG was also shown not to be of prognostic importance (p > 0.5). Our results indicates that the extent of the lateral temporal cortical resection and the ECoG findings are not important determinants of surgical outcome in patients with NLTLE.
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Object. Among the variety of surgical procedures that are performed for the treatment of medically refractory mesial temporal lobe epilepsy (TLE), no consensus exists as to how much of the hippocampus should be removed. Whether all patients require a maximal hippocampal resection has not yet been determined. Methods. At the University of Washington, all TLE operations are performed in a tailored fashion, guided by electrocorticography (ECoG). The amount of hippocampal resection is determined intraoperatively by the extent of interictal epileptiform abnormalities on ECoG recorded from that structure, resulting in a hippocampal resection that is individualized for each patient. Using this approach, the authors prospectively observed 140 consecutive patients who underwent surgery for mesial TLE with pathological diagnoses of either mesial temporal sclerosis with neuronal loss (MTS group) or mild gliosis without neuronal loss (non-MTS group) to determine whether the extent of hippocampal resection correlates with outcome when a tailored approach is used. Additionally, the authors analyzed whether the presence of residual interictal epileptiform activity on ECoG following mesial temporal resection predicts poorer seizure control. With at least 18 months of clinical follow up, 67% of the 140 patients were seizure free or had only a single postoperative seizure. There was no correlation between the size of the hippocampal resection and seizure control in the group as a whole or when stratified by pathological subtype. Using an intraoperatively tailored strategy, individuals with a larger hippocampal resection (> 2.5 cm) were not more likely to have seizure-free outcomes than patients with smaller resections (p = 0.9). Additionally, both MTS and non-MTS patients, in whom postoperative ECoG detected residual epileptiform hippocampal (but not cortical or parahippocampal) interictal activity following surgical resection, had significantly worse seizure outcomes (p = 0.01 in the MTS group; p = 0.002 in the non-MTS group). Conclusions. Intraoperative hippocampal ECoG can predict how much hippocampus should be removed to maximize seizure-free outcome, allowing for sparing of possibly functionally important hippocampus.
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An electrocorticographic (ECoG) study is reported of patients undergoing surgery for epilepsy of temporal lobe origin. During 22 en bloc resections and six out of a total of 18 amygdalo-hippocampectomies, the activity of the hippocampus was also recorded by a multipolar strip electrode placed along its axis on the ventricular surface. Patients with mesial temporal pathology, chiefly mesial temporal sclerosis, made up the majority of those selected for amygdalo-hippocampectomy. They showed a characteristic ECoG pattern, with spikes localised to the mid part of the second and third convolutions and inferior aspect of the temporal lobe. Typically, this was associated with hippocampal discharges showing an anterior maximum. Pathology involving lateral temporal neocortex and non-specific findings were associated with more widespread temporal spikes and a maximum discharge amplitude over the mid and posterior parts of the hippocampus. It is suggested that intraoperative recording of the ECoG and hippocampal activity may provide a guide to the choice between en bloc resection and amygdalo-hippocampectomy.
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We retrospectively analyzed 5 children (11-15 year) with intractable temporal lobe epilepsy (TLE) who underwent the anterior temporal lobectomy with hippocampectomy. Cases 1-3 had medial TLE (MTLE) with histologically verified hippocampal sclerosis, Case 4 had lateral TLE, and Case 5 had MTLE with old hemorrhagic lesion in the lateral temporal lobe. In Cases 3-5, chronic invasive electrocorticography recording using subdural electrodes was obtained, while in Cases 1 and 2, the epileptogenic region was defined by noninvasive preoperative evaluation. Postoperatively, Cases 1-3 became seizure free. All patients had psychosocial problems after the onset of their epilepsy, which was not improved even after the surgical control of epilepsy. Since most patients had morphological change and perfusional and metabolic disturbance outside the hippocampus at the time of surgery, earlier surgical consideration may be necessary.
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Background: Our aim was to follow up patients postoperatively to identify seizure remission and relapse after surgery, to enable individuals considering surgery to make informed choices.
Methods: Ninteen consecutive patients operated for drug resistant Temporal lobe & extra temporal lobe epilepsy between 2019 and 2020, at our centre. All the patients had at least one year post surgery follow-up.
Results: The mean age of study population was 20.87 ± 10.08 years. The mean age of onset of epilepsy in study population was 14.9 ± 8 years. There were no acute post operative seizures. The most common histpathological finding was hippocampal sclerosis in 15 patients. The patients were followed up and 15 were in the class 1 of engel classification. 2 in class 2, rest had one each
Conclusion: Following surgery approx half of patients were seizure free and Engel's favourable outcome was noted. The predictors of unfavourable outcome were younger age of onset and pronged duration and of epilepsy
Keywords: Temporal lobe epilepsy, temporal lobectomy, amygdalohippocampectomy, outcome, extra temporal lobe epilepsy, extra temporal lobectomy
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