[Pharmacoresistant temporal-lobe epilepsy. Exploration with foramen ovale electrodes and surgical outcomes]. / Epilepsia farmacorresistente del lóbulo temporal. Exploración con electrodos del foramen oval y resultados quirúrgicos.

AIM: To report our experience in the surgical treatment of temporal-lobe epilepsy. PATIENTS AND METHODS: An analysis was performed of the outcomes of 137 patients submitted to surgery between 1990 and 2001, with a follow-up of more than two years. A study was conducted of the percentages of successful detection by the different complementary tests--MRI, EEG, interictal SPECT, video-EEG with foramen ovale electrodes (FOE), neuropsychological study (NPS)--and the precision with which they reported the epileptogenic focus. RESULTS AND CONCLUSIONS: Successful surgical outcomes (Engel grades I-II): 73.4%. No surgical mortality occurred, although some mild, reversible morbidity was observed. Surgical outcomes were not affected by sex, age, age of onset and the length of time the patient had had the disease, or the frequency of the seizures. No association was found between seizures in the immediate post-operative period and a poorer long term control of the epilepsy. MR images were normal in 25% of patients; in these cases the surgical outcomes (Engel grades I-II at two years: 62%) were significantly poorer than in cases of tumours/cavernomas (86%); RMI studies of other types of lesions gave intermediate results (72%). With respect to the capacity of the different tests to lateralise/locate the epileptogenic focus, video-EEG-FOE proved to be the best, followed by MRI, SPECT, EEG and NPS.

[Prognostic value of electrocorticography in temporal lobe epilepsy: patterns of relationing mesial and neocortical activity]. / Valor pronóstico de la electrocorticografía en la epilepsia temporal: patrones de la relación mesial y neocortical.

INTRODUCTION: Electrocorticography (ECoG) monitoring in temporal lobe epilepsy (TLE) has been employed since the 40 s as a means to delineate surgical removal especially in lesional epilepsy, to reduce resection size and decrease cognitive sequelae (memory, naming). However in recent years, ECoG has been claimed to lack indications and prognostic value in cases of non lesional TLE. On the grounds of the pathophysiological relationship between mesial structures and neocortex (through propagation pathways) we have suggested a classification of ECoG activity patterns regarding the activities simultaneously recorded in mesial and neocortical grids. PATIENTS AND METHODS: Two experienced neurophysiologists (over 200 ECoG performed) have independently reviewed the recordings (including video EEG monitoring with foramen ovale electrodes) of 33 consecutive (28 non-lesional) TLE patients with the major criterion of a leading activity in mesial or neocortical areas, and related the results to the clinical course. RESULTS: As a result we identified five patterns: I. Pure mesial; II. Mesial with neocortial-related activity; III. Non-related mesial and neocortical activities; IV. Neocortical preponderance (although some mesial unrelated discharges may be seen), and V. Neocortical origin. In all 33, a tailored, ECpG-guided two-steps resection was performed. Surgical success significantly (c2 test) associated with patterns I, II and IV. Pattern V precluded a good outcome. CONCLUSIONS: ECoG reflects the state of pathological involvement of neocortex and mesial structures. An expertise approach, although brief in time (20-30 min), may either lead to preservation of relevant tissue (patterns I, II) and to establish a prognosis on the grounds of the initial epileptogenic activity.

Inhibitory neurons in the human epileptogenic temporal neocortex. An immunocytochemical study.

Immunocytochemical methods were used to study alterations in inhibitory neuronal circuits in human neocortex resected during surgical treatment of intractable temporal epilepsy associated or not with brain tumours. The epileptogenic cortex was characterized and divided into spiking or non-spiking zones by intraoperative electrocorticography (ECOG). The resected cortex was cut into blocks, sectioned and stained immunocytochemically for visualization of glutamic acid decarboxylase (GAD), the calcium-binding protein, parvalbumin (PV) and glial fibrillary acidic protein (GFAP). A variety of alterations in cortical neuronal circuits as revealed by immunocytochemical and histological methods were found. Similar alterations in inhibitory neuronal circuits appear to occur independently of the primary epileptogenic site and pathology associated with epilepsy, which suggests that there is possibly a common basic underlying mechanism that leads to seizure activity. These changes were apparently unrelated to ECOG findings at surgery, which bring into question the value of the use of interictal epileptic discharges recorded by ECOG to guide cortical resections. The most conspicuous and common change was the loss of chandelier cells. The finding that these cells are among the most vulnerable types of GABAergic interneurons in the epileptogenic temporal cortex indicates that they might be of great functional importance, since the axon terminals of chandelier cells are likely to exert powerful regulation of impulse generation in cortical pyramidal cells. Therefore, these cells might represent a key component in the aetiology of human epilepsy.