Temporal lobe epilepsy surgery modulates the activity of auditory pathway.

The purpose of this paper is to evaluate the effects of the anterior temporal lobectomy on the functional state of the auditory pathway in a group of drug-resistant epileptic patients, linking the electrophysiological results to the resection magnitude. Twenty-seven patients with temporal lobe epilepsy and a matched control group were studied. Auditory brainstem and middle latency responses (ABR and MLR respectively) were carried out before and after 6, 12 and 24 months surgical treatment. The volume and longitude of temporo-mesial resected structures were estimated on magnetic resonance images taken 6 months after surgery. Before the intervention the patients showed a significant delay of latency in waves III, V, Pa and Nb, with an increase in duration of I-V interval in comparison with healthy subjects (Mann-Whitney U-test, p<0.05). After resection, additional significant differences in waves I and Na latency were observed. Na and Pa waveforms showed a tendency to increase in amplitude, which became statistically significant 12 months after surgery for right hemisphere lobectomized patients in the midline electrode, and in Pa waveform for all patients in the temporal electrodes ipsilateral to resection (Wilcoxon test, p<0.05). In general, latency variations of MLR correlated with resection longitude, while changes in amplitude correlated with the volume of the resection in the middle temporal pole and amygdala (Pearson' correlation test, p<0.05). As a result, we assume that anterior temporal lobectomy provokes functional modifications into the auditory pathway, probably related to an indirect modulation of its activity by the temporo-mesial removed structures.

Innovative evaluation of visual field defects in epileptic patients after standard anterior temporal lobectomy, using partial field visual evoked potentials.

The purpose of this paper is to obtain an electrophysiological evaluation of visual field defects consecutive to the direct lesion of optic radiations in drug-resistant epileptic patients after a standard electrocorticographically adjusted lobectomy, and to correlate it with conventional perimetric results, and with the volume of resected tissue during surgical treatment. Twenty-four patients with temporal lobe epilepsy defined through long term EEG-video, ictal and interictal SPECT, as well as Magnetic Resonance Imaging were studied. Visual evoked potentials (VEPs) with partial and total visual field stimulation were carried out before and after 6, 12 and 24 months surgical treatment. A control group was also studied. No differences between patients and control subjects were observed during the evaluation of the full-field VEPs. However, there were statistical differences between groups in the half-field VEP recordings and in the VEP recordings of contralateral to resected side superior quadrant (CSQ) before lobectomy and 6 months later (Mann-Whitney's U-test, p<0.05). Significant associations were found between VEP abnormalities and perimetric results in CSQ. A close relationship between perimetry, VEPs and volume of the resected tissue in hippocampus, parahippocampus, medial and lower temporal giri was also found. Visual field defects consecutive to standard temporal lobe resection in epileptic patients could be objectively evaluated by partial stimulation VEPs corresponding to the size of resected tissue.

A neurofunctional evaluation strategy for presurgical selection of temporal lobe epilepsy patients.

Introduction Temporal lobe epilepsy (TLE) is the prototype of a surgically correctable syndrome. Successful surgical outcomes depend on a thorough presurgical evaluation aimed primarily at identifying the epileptogenic zone. Objective Describe the noninvasive presurgical selection and evaluation strategy for TLE patients introduced at the International Neurological Restoration Center (CIREN) in Havana, Cuba, and evaluated between 2001 and 2006 for its accuracy in identifying candidates for non-lesional resection surgery. Methods Ictal onset electrographic patterns of 1,679 seizures in 72 patients with drug-resistant partial epilepsy, obtained through longterm scalp Video EEG (V-EEG) monitoring, were evaluated. The correlation between the V-EEG-defined epileptogenic zone and the dysfunction shown by single photon emission computed tomography (ictal and interictal brain SPECT) and nuclear magnetic resonance spectroscopy (MRS) was established. Results V-EEG monitoring determined that 44.4% of evaluated patients had complex partial temporal lobe seizures. Identification of patients with medial temporal epilepsy (MTE) increased as a result of lateralization and localization of the dominant mean ictal pattern frequency (5.56 ± 1.31 Hz) during the period of maximum spectral power VARETA localization of an ictal epileptiform activity source coincided with the epileptogenic zone in all TLE patients who subsequently underwent a successful temporal lobectomy. Semiquantitative analysis of ictal and interictal brain SPECT images, as well as metabolic ratios measured by MRS, combined with V-EEG findings, enabled localization/lateralization of the epileptogenic zone in TLE patients whose MRIs were normal or showed bilateral structural abnormalities. Conclusions Confirmation of correct localization/lateralization of the epileptogenic zone following successful surgical outcomes in selected TLE patients led CIREN to develop a surgical treatment strategy for patients in Cuba with drug-resistant temporal lobe epilepsy. This strategy offers an appropriate, cost-effective treatment alternative for developing countries like Cuba, with the benefit of significantly improving TLE patients' quality of life.