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Introduction: Deep brain stimulation (DBS) in drug-resistant epilepsy has been applied to several brain targets. However, its exact mechanism of action is not known, and the diversity of targets makes it difficult to know the degree of evidence that supports its use., Development: A review of the literature on DBS for drug-resistant epilepsy was conducted. The efficacy of DBS in drug-resistant epilepsy seems to be mediated by a desynchronisation of neuronal activity at the epileptogenic focus or a modulation of the «circuitopathies» that exist in epilepsy, depending on the target. In DBS multiple cortical and subcortical structures have been used, but class I evidence exists only for DBS of the anterior nucleus of the thalamus., Conclusions: DBS in epilepsy is still under investigation, with class I evidence for DBS of the anterior nucleus of the thalamus. The rest of the targets have yielded variable results that must be confirmed with randomised designs in larger series.

Introduction: Transient global amnesia (TGA) is a perfectly well defined clinical picture, but nevertheless even today its aetiology remains unknown. The three most widely accepted theories suggest it has a vascular origin, it is related with the pathophysiology of migraine or it is of an epileptiform nature., Aim: To analyse whether there is an electroencephalographic pattern that is consistently repeated in a series of electro-encephalograms (EEG) carried out on patients with TGA., Patients and Methods: The study consists in a retrospective analysis of a sample of 345 patients referred to have an EEG after an episode of TGA., Results: In almost 20% of the EEGs something that could be considered abnormal was found, although most of these findings (64%) were of little pathological significance. Of the remaining 26%, attention should be drawn to the cases of two patients with subclinical rhythmic electroencephalogram discharges of adults (a pattern with a meaning that is not altogether clear and which has previously been associated with TGA)., Conclusions: A considerable percentage of patients have TGA and EEG alterations, although most of them are of scarce pathological significance or can be attributed to some other underlying condition. We have not succeeded in identifying any pattern that is consistently repeated. Our results suggest that the EEG is a test with low diagnostic effectiveness in this pathology and it is necessary to reconsider the need to systematically perform such tests in suspected cases of TGA.

Introduction: Electroencephalogram (EEG) recordings reflect different oscillatory activities during slow wave sleep (stages 2 and 3-4 of the sleep-waking cycle), namely d oscillations (< 4 Hz), sleep spindles and K complexes. These activities are essentially generated by the activity of the thalamo-cortical relay neurons, the neurons of the thalamic reticular nucleus and by the neurons in the cerebral cortex., Development: The combination of the intrinsic electrophysiological properties of the thalamic and cortical neurons, together with their synaptic connections, are responsible for the generation of these oscillations. Extra or intracellular recordings of these neurons during spontaneous or anaesthetic-induced sleep show how these neurons change their electrical activity during slow sleep due to the hyperpolarization of their membrane potential. Thus, the thalamic neurons lower their response to sensory stimuli and filter this information towards the cerebral cortex. Glial cells also contribute to the generation of the d waves seen in the EEG and oscillate synchronously with the cortical neurons. In addition, the oscillations of this neuronal and glial network is linked to important changes in the concentration of certain ions in the extracellular space; for instance, the K+ and Ca2+ concentration oscillates synchronously with the neuronal and the glial activity., Conclusions: The oscillations in the EEG, which are slower than those observed in the waking state or in paradoxical sleep, play a fundamental role in processing the information handled by the central nervous system and filter the irrelevant information towards the cerebral cortex.

Objectives: The homeostatic regulation of sleep is based on the model devised by Borb ly in 1982. During the sleep waking cycle there is an interaction between the natural tendency to sleep, which increase as the vigil is prolonged (S process) and the circadian variation (C process). In this study, we aimed to find how slow activity (0.5 4.5 Hz) during sleep (SWA), mainly registered in phases 3 and 4, may be an indicator of process S., Patients and Methods: We compared two groups of persons: 10 with chronic sleep deprivation (CSD) (less than 6 hours of sleep/day) as compared with 10 persons who slept more than 6 hours per day, using spectral analysis of their delta activity during sleep., Results: There was a predominance of delta activity in the group of persons with CSD as compared with the control group., Conclusions: An increase in SWA was accompanied by an increased tendency to sleep and may therefore be considered to be a marker for this. This marker allows conditions associated with hypersomnolence due to alteration of process S to be identified.

Introduction: The clinic usefulness of a diagnostic test is in relationship to the precision with which measures the studied phenomenon. The lack of precision involve the reliability upon causing confounded results of the normal and diseased populations., Objective: Since the sleep varies in function of the age, to find sleep parameters that fit better to the changes that the aging produces in the sleep., Material and Methods: Spectral analysis through the Fast Fourier Transformation of the ambulatory EEG of 28 healthy subjects., Results: Maximum value of power (maximum depth) in a frequency of ended in a point of the sleep goes losing in a way specifies and systematical with the age., Conclusions: The variance accounted by this parameter is of the 87%, what, being tried to a phenomenon so variable as the sleep, supposes a interesting starting point to be applied to some pathologies in those which is presumed that the slow sleep (to which is attributed a paper in the cerebral restoration) is decreased.

Spectral EEG analysis techniques were used to evaluate the degree of hepatic encephalopathy in a group of 69 cirrhotic patients, as compared to the results obtained in a group of healthy controls. With respect to controls, the cirrhotics had stronger delta and theta bands, and a weaker alpha band, as well as a reaction of the alpha band to opening the eyes. The use of strength ratios between different bands of frequency increments the sensitivity and diagnostic reliability of this technique, particularly the delta/alpha and theta/alpha indices, and permits the detection of cases with subclinical encephalopathy, which is particularly useful for clinical follow-up and for the evaluation of different therapeutic regimens.