The first case of invasive EEG monitoring for the surgical treatment of epilepsy: Historical significance and context

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.