George H. Klem

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During the First International EEG Congress, London in 1947, it was recommended that Dr. Herbert H. Jasper study methods to standardize the placement of electrodes used in EEG (Jasper 1958). A report with recommendations was to be presented to the Second International Congress in Paris in 1949. The electrode placement systems in use at various centers were(More)
Functional localization prior to cortical resections for intractable seizures has usually been performed in the operating room in awake patients. Chronically placed subdural electrodes offer the possibility of performing such testing outside of the operating room and without the unavoidable stresses and time limitations of the surgical setting. The use of(More)
We have evaluated the afterdischarge thresholds and functional response thresholds in 21 patients with chronically implanted arrays of subdural electrodes. Afterdischarge thresholds varied from 2 to greater than 15 mA over the tested cortex, by as much as 12 mA in individual patients, and by as much as 12 mA between adjacent electrodes. Thresholds for(More)
Electrical stimulation studies have demonstrated that a "supplementary motor area" (SMA) exists in humans. However, its precise functional organization has not been well defined. We reviewed the extraoperative electrical stimulation studies of 15 patients with intractable epilepsy who were evaluated with chronically implanted interhemispheric subdural(More)
PURPOSE Malformations due to abnormal cortical development (MCDs) are common pathologic substrates of medically intractable epilepsy. The in situ epileptogenicity of these lesions as well as its relation to histopathologic changes remains unknown. The purpose of this study was to correlate the cellular patterns of MCDs with the expression of focal cortical(More)
BACKGROUND Despite lateralizing signs, clinical lateralization of partial seizures may be difficult. We evaluated the usefulness of ictal unilateral blinking as a new lateralizing sign. METHODS We retrospectively searched our seizure database over a 30-month period and collected videotapes of patients with ictal unilateral blinking. After initial review,(More)
With the aid of chronic subdural electrodes we have been able to record from the posterior banks of the sylvian fissure, auditory evoked potentials (AEPs) that had morphologies and peak latencies compatible with the primary AEPs described by Celesia and Puletti (1969). These AEPs had amplitudes that were not only affected by the side of stimulus(More)
OBJECTIVE To investigate the lateralization and localization of ictal EEG in focal epilepsy. METHODS A total of 486 ictal EEG of 72 patients with focal epilepsy arising from the mesial temporal, neocortical temporal, mesial frontal, dorsolateral frontal, parietal, and occipital regions were analyzed. RESULTS Surface ictal EEG was adequately localized in(More)
To study the distribution of the early (first 80 ms) human cortical potentials evoked by stimulation of the posterior tibial nerve at the ankle, scalp electrodes were placed within a 12-cm radius from the vertex and were separated by approximately 3 cm. With unilateral stimulation the response at the hemisphere ipsilateral to the stimulus was consistently(More)