Summary:Purpose: Prospective evaluation of risk factors for posttraumatic epilepsy (PTE) by using clinical, EEG, and brain computed tomography (CT) data in four assessments from the head injury (HI) acute phase to 1 year later; and evaluation of the possible epileptogenic role of hemosiderin as shown by brain magnetic resonance imaging (MRI).Methods: Risk factors for PTE were evaluated by using Kaplan-Meier curves, log-rank test, and the Cox model in 137 consecutively enrolled adult inpatients. Percentage differences of patients with brain hyperintense and/or hemosiderin areas shown by MRI 1 year after HI were statistically evaluated by univariate tests considering two subgroups [e.g., patients with (FTE) and without (WLS) late seizures].Results: The PTE subgroup included 18 patients with at least two seizures between the second and twelfth months. KaplanMeier curves demonstrated that Glasgow Coma Scale low score, early seizures, and single brain CT lesions are PTE risk factors, as is the development of an EEG focus 1 month after HI. No significant percentage difference was found between PTE and WLS patients with hemosiderin spots shown by MRI 1 year after HI.Conclusions: the Cox model indicates that, for HI patients with early seizures and brain CT single temporal or frontal lesions in the acute phase, the PTE risk is 8.58 and 3.43 times higher, respectively, than for those without. An EEG focus 1 month after HI is a risk factor 3.49 times higher than for patients without such EEG changes. One year after HI, a higher percentage of PTE than WLS patients had cortical MRI hyperintense areas including hemosiderin. Key Words: Posttraumatic epilepsy-Clinical-Brain CT-MRI-EEG follow-upHemosiderin.Posttraumatic epilepsy (PTE), known since the time of Hippocrates, is still a puzzle because of the variety of methods used in the different studies and the wide range of their results. Dalmady-Israel and Zasler ( I ) provided a critical analysis of the literature on PTE emphasizing the lack of standardized definitions of both epilepsy and head injury (HI). Differences in inclusion/exclusion criteria and inadequacy in the follow-up of patients generate inconclusive or controversial results on incidence and risk factors.Many of the retrospective studies evaluated outcome when there was no standardized way of managing the

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Electroencephalographic (EEG) patterns were analyzed in a group of ambulatory patients who ranged in age and sex using spectral analysis as well as Directed Transfer Function, a method used to evaluate functional brain connectivity. We tested the impact of window size and choice of reference electrode on the identification of two or more peaks with close frequencies in the spectral power distribution, so called “split alpha.” Together with the connectivity analysis, examination of spatiotemporal maps showing the distribution of amplitudes of EEG patterns allowed for better explanation of the mechanisms underlying the generation of split alpha peaks. It was demonstrated that the split alpha spectrum can be generated by two or more independent and interconnected alpha wave generators located in different regions of the cerebral cortex, but not necessarily in the occipital cortex. We also demonstrated the importance of appropriate reference electrode choice during signal recording. In addition, results obtained using the original data were compared with results obtained using re-referenced data, using average reference electrode and reference electrode standardization techniques.

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The problem of the relationship between stimulus intensity and kindling effect was studied in three groups of cats with bipolar stimulating electrodes implanted in the right posterior sigmoid gyrus (sensorimotor cortex). Daily stimulation with a 1-sec train of 60-Hz rectangular pulses was carried out in 17 cats over a period of from 27 to 265 days. Group I, 3 cats, was stimulated with a current intensity of 200 microA, peak-to-peak, which was subthreshold for afterdischarges (ADs); 6 animals from group II were stimulated with near-threshold currents (0.8--1.1 mA); and in the 8 animals of the group III, the ADs were evoked by threshold currents of 1.0--1.6 mA. The EEG was recorded from the sensorimotor and visual cortices, hippocampus, caudate nucleus, dentate nucleus, and cerebellar cortex. It was found that the low-current stimulation (200 microV) was not effective in inducing kindling. Near-threshold stimulation (below 1 mA) resulted in the development of bioelectrical epileptic activity in most cats. Threshold stimulation for AD resulted in the development of bioelectrical spontaneous activity and in an increase in the duration of ADs, as well as in generalized tonic-clonic seizures during cortical stimulations, in the majority of cats. Differences in hippocampal and neocortical kindling in cats are discussed in terms of ADs and seizure development. It was found that (1) a longer time was required for neocortical than for hippocampal kindling (3--10 weeks), and (2) there was greater variability in the effects of neocortical kindling. Secondary generalized seizures developed in the group with threshold stimulation for AD and were preceded by an increase in the number of ADs. The interictal epileptic activity developed in some cats in the absence of ADs.

The aim of this study was to estimate spectral properties and propagation of the EEG signals registered during sevoflurane anaesthesia between individual EEG recording channels. The intensities of activity flows were calculated for delta, theta, alpha and beta waves using the Directed Transfer Function integration procedure. It was found that delta waves played the dominant role in the EEG signal propagation during anesthesia and it was suggested that theta and alpha waves propagation could be related to the processes participating in the wakefulness control. Data obtained with DTF method were compared with data received from the analysis of cerebral blood flow with the use of PET in other laboratory. This study showed that analysis of the EEG signal propagation is useful for better understanding and thus safer induction of anaesthesia procedure.

Carbamazepine (CBZ) effects on (a) complex partial seizures and afterdischarges (AD), (b) memory retrieval, and (c) conditioned avoidance response (CAR) latencies were studied in a group of 9 hippocampally kindled cats. Significant AD and epileptic seizure suppression was observed in kindled cats after administration of CBZ concurrent with significant improvement in percentage scores on the memory retrieval test. The CAR latencies were longer in kindled cats with or without CBZ than in the conditioned group of cats without both kindling and CBZ. CAR latencies were not significantly different between kindled and kindled-CBZ-treated cats. Thus, the longer latencies in kindled animals cannot be due to CBZ but apparently are related to the effects of kindling. In some kindled animals, longer CAR latencies were reversed by CBZ.