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Summary: A retrospective clinical study is presented which is based on 133 patients with uncontrolled temporal lobe seizures who underwent bilateral stereoelectroencephalographic exploration. The aim of the study was to evaluate quantitatively the degree of agreement among spontaneous and chemically and electrically induced seizures, as well as between each of these seizures and the spontaneous interictal activity (“spiking”). To simplify the problem, only the side of origin and not the exact site of onset of the ictal discharge within the temporal lobe was dealt with. Special attention was paid to whether or not a seizure propagated to the homotopic regions of the opposite hemisphere, thus dealing with the still controversial question of the independent secondary epileptogenic lesion or “mirror” focus in man. The clinical outcome of surgery in 64 cases of temporal lobe epilepsy in which the operation was based on the conclusions of the SEEG exploration with or without recording of spontaneous seizures confirmed the outstanding importance of the spontaneous seizures in identifying the side of the primary epileptogenic zone. The degree of positive correlation between the spontaneous and the induced seizures varied from 77% for the electrically and 60% for the chemically induced seizures. On the other hand, the spontaneous interictal activity agreed only in approximately two‐thirds of cases: best with the electrically induced and less with the spontaneous seizure. Chemically induced seizures agreed the least. The authors conclude: (1) Because of relatively frequent discrepancies between the side of onset of the seizures and the lateralization of interictal epileptic activity, the recording of seizures is of primary importance for assessing the results of the SEEG examination. (2) The recording of spontaneous seizures is preferable to that of electrically or chemically induced seizures. (3) The reliability of the lateralization suggested by electrically induced seizures is somewhat higher than that of chemically provoked seizures. (4) Special caution should be exercised in determining the lateralization of seizures with contralateral propagation. RÉSUMÉ Une étude clinique rétrospective est faite sur 133 malades présentant une épilepsie du lobe temporal résistant à la thérapeutique et ayant subi une exploration stéréo‐EEG bilatérale. Le but de ce travail est Ďévaluer quantitativement les rapports entre les différents types de crises (spontanées, induites par des moyens chimiques et par la stimulation électrique). Une corrélation a également été faite entre les différents types de crises et Ľactivité intercritique spontanea (pointes). Pour simplifier le probleme, seul le côté de la décharge critique onginelle dans le lobe temporal a été envisage. Un interet particulier a porte sur le probleme de la propagation dventuelle aux regimes homologues de l'hemisphere oppose dans le but de discuter la question controversy des lesions epileptogènes secondares indépendantes ou des “foyers en miroir” chez l'homme. Les interventi...

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An apparent discrepancy exists between the remarkable language competence of the isolated right cerebral hemisphere in some split-brain patients and the lack of language competence in some aphasic patients in whom only the left cerebral hemisphere has been damaged. This has led to a revival of the idea that the dominant cerebral hemisphere inhibits the potential functioning of its partner. We tested this model of interhemispheric inhibition in four patients with unilateral limbic seizures (three left-sided, one right-sided). While seizure activity was monitored with bilaterally implanted stereotactic EEG depth electrodes or bilateral foramen ovale EEG electrodes, the patients were tested in lateralized hemisphere-specific tachistoscopic recognition experiments. In two patients performance was correlated with the electrical pattern during prolonged unilateral subclinical limbic status epilepticus, and in two patients performance and intracranial electrical activity were compared before, immediately after and during the recovery phase of left limbic complex partial seizures with postictal aphasia. Three main findings were obtained. (i) Focal unilateral limbic seizure activity in the depth interferes with cognitive functions, even when unnoticed clinically or undetectable on the surface EEG, provided that epileptiform EEG activity lasts for several seconds. (ii) This interference is specific to the cognitive functions associated with the 'dominant' processing of the discharging hemisphere. (iii) Seizure-induced impairment of the 'dominant' functions of the discharging hemisphere is associated with improvement of performance of the same function by the other hemisphere. Although each patient's clinical and experimental situation differed, the converging results support the hypothesis of hemispheric interaction based upon functional inhibition for verbal processing in patients with a left hemispheric focus. The reverse situation, namely facial processing in a single case with a right hemisphere focus, remains inconclusive.

Cerebral glucose utilisation using ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) was measured in 4 patients with temporal lobe epilepsy during a selective anterior temporal lobe (TL) amobarbital test (ATLAT) and compared with their baseline values. ¹⁸F-FDG was injected intravenously immediately after administration of amobarbital into the anterior choroidal artery (acha) in the case of the superselective ATLAT and into the territories of acha, posterior communicating artery, and ophthalmic artery in the case of the ATLAT using the temporary balloon occlusion technique. A decrease in glucose uptake as a result of amobarbital application was observed in ipsilateral temporolateral (4 patients), ipsilateral temporomesial (2 patients) and bilateral frontolateral (1 patient) cortices. All patients showed decreased glucose uptake in contralateral temporolateral regions. Cerebellar diaschisis was observed in 2 patients. In conclusion, although aimed at selective inactivation of the mesiobasal TL structures, the ATLAT does not result in exclusive selective glucose hypometabolism of these structures. Relatively widespread ipsilateral and contralateral effects were observed suggesting local and remote metabolic deafferentation. No association was observed between the glucose uptake, clinical or memory performance.