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The purpose of this study was the development of a real-time filtering procedure of MRI artifacts in order to monitor the EEG activity during continuous EEG/fMRI acquisition. The development of a combined EEG and fMRI technique has increased in the past few years. Preliminary "spike-triggered" applications have been possible because in this method, EEG knowledge was only necessary to identify a trigger signal to start a delayed fMRI acquisition. In this way, the two methods were used together but in an interleaved manner. In real simultaneous applications, like event-related fMRI study, artifacts induced by MRI events on EEG traces represent a substantial obstacle for a right analysis. Up until now, the methods proposed to solve this problem are mainly based on procedures to remove post-processing artifacts without the possibility to control electrophysiological behavior of the patient during fMRI scan. Moreover, these methods are not characterized by a strong "prior knowledge" of the artifact, which is an imperative condition to avoid any loss of information on the physiological signals recovered after filtering. In this work, we present a new method to perform simultaneous EEG/fMRI study with real-time artifacts filtering characterized by a procedure based on a preliminary analytical study of EPI sequence parameters-related EEG-artifact shapes. Standard EEG equipment was modified in order to work properly during ultra-fast MRI acquisitions. Changes included: high-performance acquisition device; electrodes/cap/wires/cables materials and geometric design; shielding box for EEG signal receiver; optical fiber link; and software. The effects of the RF pulse and time-varying magnetic fields were minimized by using a correct head cap wires-locked environment montage and then removed during EEG/fMRI acquisition with a subtraction algorithm that takes in account the most significant EPI sequence parameters. The on-line method also allows a further post-processing utilization.

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Using functional MRI (fMRI) with concurrent EEG monitoring the authors studied cortical activation associated with epileptiform discharges in three patients with fixation-off sensitivity. The EEG paroxysmal activity elicited by eliminating central vision correlated significantly with an increased blood oxygen level-dependent signal in the extrastriate cortex (Brodmann areas 19 and 37). fMRI provides a unique opportunity for localizing precisely the cortical areas generating paroxysmal activity in patients with fixation-off sensitivity.

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This review looks at the magnetoencephalogram (MEG) studies on generalized epilepsy starting from the first cases investigated up to the most recent contributions regarding the photoconvulsive response and the results obtained applying the template analysis. As far as the spike-and-wave complex is concerned, in the cases both of photoconvulsive response and of non-generalized epilepsy, a primary multiregional participation of the cerebral cortex is shown, which, variable in time and often with a side prevalence, is alternated by bisynchronous epileptiform activity starting from midline structures.

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The neuromagnetic method was applied to the study of photoconvulsive responses. The identification of specific magnetic field distributions over the scalp was achieved by; (a) a stimulation paradigm consisting of series of trains of flicker stimuli randomly presented to the epileptic patient, after eye closure, to get epileptic responses while avoiding seizures; (b) a novel procedure for data analysis, to select consistent responses. These patterns, when sufficiently stable in time and dipolar in shape, were used for source localization in the usual biomagnetic framework of the equivalent current dipole source representation. The results of this approach suggest that different specific cortical areas are repeatedly and randomly activated, involving mainly the frontal, occipital and temporal areas, often with a hemispheric prevalence.

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A systematic investigation of several cases of focal epilepsy has been performed in an unshielded environment using a 4-channel neuromagnetic sensor. The localizations provided by the magnetic measurements have been compared with clinical evidence and confirmed by X-ray findings, and in one case also by intracranial surgery. The results show the importance of simultaneous detection of magnetic fields at different sites of the scalp in order to get a dynamic view of the epileptic activity and to detect multifocal activity unsuspected on the basis of the EEG investigation.

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In the last few years there has been an increasing interest in the magnetic activity due to bioelectrical currents flowing in the brain. In this paper preliminary results are reported concerning spontaneous magnetic brain activity in 36 patients affected by different kinds of brain disease; in most of these cases the symptoms were induced by localized pathology (atrophies, scars, tumors). Measurements were carried out with the simultaneous recording of the EEG. At present one of the most interesting features of magnetic detection seems to be its high localizing ability in cases of cortical foci, and sometimes its ability to show activities not evident in the EEG. These features seem to be very encouraging for the search for technical improvements, with the aim of making the magnetic technique a candidate for current diagnostic purposes.

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