30 research outputs found

    Postoperative interictal spikes during sleep contralateral to the operated side is associated with unfavourable surgical outcome in patients with preoperative bitemporal spikes

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    AbstractPurpose: To correlate the persistence of contralateral spikes during sleep after unilateral surgery with seizure outcome in a temporal lobe epilepsy (TLE) population and to test the existing hypotheses about the origin of the contralateral spikes in temporal lobe epilepsy. Methods: In the 19 patients selected for this study unilateral temporal lobe surgery was performed. To investigate the course of bilateral interictal epileptiform discharges observed before surgery in awake or sleep over the temporal lobe contralateral to surgery, 24h mobile 12 channel EEG recording was performed at minimum two, in average 4.6 (2–10) years after the surgery. Results: The association of postoperative contralateral spikes and non-seizure free outcome was highly significant. The existence of unilateral pathology before surgery was highly predictive for good outcome and disappearance of contralateral spikes. The association between good seizure outcome, disappearance of contralateral spikes and the existence of unilateral pathology before surgery was also significant. Our data partially satisfies the expectations of both the “seizure induced” and mirror type secondary epileptogenesis hypotheses concerning origin of contralateral spikes, but were not completely congruent with either of them. Conclusions: Unfavourable surgical outcome in a temporal lobe epilepsy group with preoperative independent bilateral interictal spikes was associated with the persistence of postoperative contralateral spikes and lack of unilateral pathology. Compared with seizure outcome the presence/absence and distribution of postoperative interictal spikes in NREM sleep not entirely fit to the predictions of existing secondary epileptogenesis hypotheses

    Increased mesiotemporal delta activity characterizes virtual navigation in humans

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    Hippocampal theta or rhythmic slow activity (RSA) occurring during exploratory behaviors and rapid-eye-movement (REM) sleep is a characteristic and well-identifiable oscillatory rhythm in animals. In contrast, controversy surrounds the existence and electrophysiological correlates of this activity in humans. Some argue that the human hippocampal theta occurs in short and phasic bursts. On the contrary, our earlier studies provide evidence that REM-dependent mesiotemporal RSA is continuous like in animals but instead of the theta it falls in the delta frequency range. Here we used a virtual navigation task in 24 epilepsy patients implanted with foramen ovale electrodes. EEG was analyzed for 1-Hz wide frequency bins up to 10 Hz according to four conditions: resting, non-learning route-following, acquisition and recall. We found progressively increasing spectral power in frequency bins up the 4 Hz across these conditions. No spectral power increase relative to resting was revealed within the traditional theta band and above in any of the navigation conditions. Thus the affected frequency bins were below the theta band and were similar to those characterizing REM sleep in our previous studies providing further indication that it is delta rather than theta that should be regarded as a human analogue of the animal RSA
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