EEG-EMG Zeitschrift fur Elektroenzephalographie, Elektromyographie und verwandte Gebiete最新文献

In 22 patients with apallic syndrome brainstem auditory and somatosensory evoked potentials were recorded, in 8 patients the course during rehabilitation was observed. Clinically the patients were scored with Glasgow-coma scale, Karnofsky-index and Goldenberg-scale. The outcome of rehabilitation was estimated by the "Glasgow-outcome scale". No correlation was found between results of evoked potentials and clinical state. First evoked potentials measurements of apallic patients allowed no prognosis. Evoked potentials are an important prognostic factor after severe head trauma, but have no value for the prognosis of apallic patients.

In 19 patients with herpes simplex encephalitis 64 EEG examinations and 36 CT scans have been performed within the first two weeks after onset of clinical symptoms. During the first 10 days periodic discharges were present in 12 patients. At this time CT scan was negative in 5 of them. Five of 7 patients without but only 4 of 12 patients with this EEG pattern survived without clinical abnormalities. Five patients with periodic discharges died during the acute stage of the illness. In patients with poor outcome including major clinical deficit or death periodic discharges were present during successive investigations until day 14. In the group of patients with good clinical improvement these EEG changes were only detected in a single recording until day 7. Periodic discharges have to be considered as an indicator of a poor prognosis whenever they are present for a longer period.

The effect of increasing static magnetic field strength up to 4.7 Tesla on the electrical function of the cat brain was studied by EEG frequency analysis and recording of somatosensory evoked potentials. While the latencies of the peaks P6 and P10 of the somatosensory evoked potentials were stable during the time course of the experiment, EEG intensity, EEG frequency index and the P10/N15 amplitude showed substantial fluctuations. EEG intensity varied between 67 and 156%, and EEG frequency index between 65 and 140% of the mean value averaged over the whole length of the experiment. The P10/N15 amplitude even varied between 16 and 186% of the mean amplitude. Despite these variations none of the variables correlated with the strength of the magnetic field. The observed changes are therefore interpreted as spontaneous fluctuations of vigilance and not as effects of the static magnetic field.

The amount of event-related decrease of increase in alpha-band power is termed "Event-Related Desynchronization" or ERD. In this study, ERD is used as an index of cortical activation, which not only can be applied to monitor poststimulus but prestimulus processes as well. Usually, ERD is analyzed within a fixed range of alpha-frequency, typically within a range of 8-12 Hz. alpha-frequency, however, shows a considerable between subject variation, even in a sample of subjects with comparable age. The purpose of this study, thus is to show as to how the range of alpha-frequency affects the calculation of ERD. Two different methodological approaches were compared. First, ERD was calculated within a fixed range of 8-12 Hz. Second, ERD was calculated within an individual range, which was adjusted to the individually determined alpha-frequency of each subject. A sample of ten right handed subjects participated in an episodic memory experiment, in which target words, shown in a earlier session of the experiment, were to be identified. A time span of 375 ms preceding and following the presentation of a word was defined as the "pre-" and "poststimulus" interval. EEG-signals were recorded unipolarly from 29 leads. The results show a rather localized increase of ERD in the poststimulus interval. In the prestimulus interval on the other hand, the average magnitude of ERD is much lower and the topographical distribution less localized. Most importantly, however, when comparing the two methods of analyzing ERD, those ERD-values calculated within an individually determined alpha-band, are superior in order to differentiate between the pre- and poststimulus interval.

Obviously, in static magnetic fields the isotropic distribution of cortical electrical charge movements becomes an anisotropic state. By this effect we have the phenomenon that the spontaneous EEG is triggered by external Zeitgeber like electrical stimuli of N. medianus or internally by the ECG. This orientation of charge transports leads to an additional varying magnetic field which induces currents in coils placed at the same positions like EEG-electrodes.

The on-going EEG contains information on thinking strategies during cognitive and creative tasks and during listening to music. This was demonstrated by a method taking use of the fact that both the amount of local current production and the degree of electric coupling of brain regions is characteristically changed by mental tasks. In groups of volunteers the significant changes of absolute power and coherence caused by different mental tasks are computed and entered into schematic brain maps (EEG probability maps). The results indicate the existence of general brain strategies even in mental activities as specific as those referred to above. Moreover, several relationships between EEG, psychological test scores, degree of special education and intelligence were found. Studies with extreme value validation according to intelligence and creativity test scores yielded significant differences between the groups of the best and the poorest performers during a creative task in the EEG. The EEG thus can be conceived of as deterministic chaos with different degrees of organization according to its information content. In this context, the question arises as to a possible function of the EEG for the optimization of thinking processes.

Motor evoked potentials (MEP) were recorded in a total of 145 patients with supratentorial (N = 29), infratentorial (N = 25) and spinal (N = 91) lesions affecting the descending pathways. In all cases potentials were evoked by electrical, in addition in 55 of them by electromagnetic stimulation of the motor cortex. The peripheral conduction time was determined in all patients by electrical stimulation of the cervical and lumbar nerve roots, respectively. This study was designed to compare both stimulation techniques (electrical vs. electromagnetic) regarding their significance in recording of potentials as well as in correlation of potentials with the motor status as established by clinical examination. Our results show that potentials were obtained in 87.6% following central (cortex) and in 100% following central electromagnetic stimulation. 87.9% of the recordings in infratentorial and spinal lesions show a correct and 12.2% a "false positive" correlation with the clinical motor status. On the other hand, the correlation was false negative in 13.8%, correct in 79.3% and "false positive" in 6.9% of the supratentorial cases. There was no difference between electrical and electromagnetic stimulation regarding diagnostic significance of potentials. Our results allow the following conclusions: both electrically and electromagnetically evoked potentials are sensitive for electrophysiological assessment of infratentorial and spinal lesions, but unreliable in evaluation of supratentorial lesions, especially in the acute stage. Due to its painlessness, electromagnetic stimulation is the method of choice for transcranial eliciting of MEP in the awake patient, who is capable of facilitation by voluntary background contraction of the target muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

It will be reported about 142 EEG spectral analytic mappings in 100 patients with focal EEG findings which were recorded already in routine EEG examinations. Drawings of the visually analysed paper recordings have been compared with the maps. We found in about 30 per cent a true gain of information. It is based on a more precise demarcation of focal findings or a better display of points of most severe dysfunction within extended disturbances. Beyond that the pictorial presentation of topographic features is a general advantage of EEG mapping. On the other side there are limits and disadvantages of topographic EEG analysis. With special reference to the analysis of circumscribed dysfunctions they will be demonstrated. Problems are related to the type of reference, to the choice of analysis time, or to "spatial aliasing effects" which are introduced by the interpolation procedure of mapping analysis. Beside the neuroradiological imaging methods the EEG mapping maintains special significance because it displays the functional aspect of cerebral processes.

Visual evoked potentials, including the P300 response, and reaction time were recorded from 20 patients with multi-infarct dementia, 20 nondemented patients with brain-infarct diseases, and 20 age-matched control subjects. Additionally the patients were assessed using the WAIS-index. Prolonged P300 latency and reaction time occurred in both of the patient-groups, correlated significantly with the WAIS-index. However, effects regarding to P300 latency and reaction time were not strong enough to allow individual classifications.

This study investigated the usefulness of the Contingent Negative Variation (CNV) in the assessment of therapeutic efficacy of a nootropic substance, Cerebrolysin. A total of 41 geriatric patients with the diagnosis of moderate organic brain syndrome of different etiology were included in this randomized placebo-controlled double-blind study. After ten Cerebrolysin- plus multi-vitamins-Infusions, the treatment group of 27 patients showed a significant CNV-amplitude increase as compared to pre-treatment values. In the placebo group of 14 patients CNV-amplitudes even decreased after ten Infusions with multi-vitamins alone. These findings were interpreted in line with the vigilance model of nootropic drug effects as a vigilance-increasing effect of Cerebrolysin, i.e. as an increased neuronal performance readiness. The results confirmed the usefulness of the CNV method by providing an EEG-index of nootropic drug effects.