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

In 163 patients with focal cerebral lesions, 43 of them with completed stroke, 43 patients with TIA, 33 patients with ICH and 29 patients with malignant and 15 patients with benign tumors EEG mapping and CT was performed. The results of EEG mapping obtained using automated artifact detection were compared to those achieved by means of visual control of raw EEG. Furthermore the impact of long (850 +/- 250s) or short (32s) analysis time was studied. Eliminating artifacts by means of visual control of raw EEG significantly more positive results were obtained than using automated artifact detection. That was found in patients with as well as in patients without lesions in CT. In relation to etiology a significant difference was found only in cerebrovascular diseases but not in the other patients-groups. Corresponding results were found in 75% of the patients. The visual control provided additional lateralization especially in patients with CS (37%) and TIA (26%). A longer duration of analysed EEG epochs did not increase the number of focal changes in EEG mapping.

The somatosensory evoked cortical potentials were investigated for 35 healthy children (17 boys, 18 girls) between 6 and 17. The stimulation of the N. tibialis was affected at the Malleolus medialis using surface electrodes; the derivation was likewise conducted according to the ten-twenty system using surface electrodes. Investigations carried out employing this methodology demonstrate that the SEP's of the N. tibialis from the N30 to the N70 are clearly measurable in the children. The N30, P40 and N50 could be presented with the smallest standard deviations and side differences. The latencies of N30 and P40 show significant dependencies on the height of the children. Influence of gender could be demonstrated more for the latency of the N30 in from of longer latencies in boys that in girls which were independent of body size.

33 patients with intracerebral hemorrhage were studied and the findings of EEG mapping, routine EEG and CT were compared. It could be shown, that the EEG mapping revealed in 6 patients additional focal changes corresponding with the clinical signs compared to conventional EEG. Identical results of EEG mapping and CT were found in 27 patients. In 5 patients the focal changes were localised contralateral to the hyperdense lesion in CT, and in 1 patient the EEG mapping failed to show any lateralisation. A negative intercorrelation between the size of the hematoma and the frequency, which revealed the focal signs in EEG mapping, could be shown.

Recent research on the relationship between ERP-latencies and reduced information process capabilities with demented subjects has yielded divergent results. In the present study P300-latencies and RT are used in an attempt to differentiate between demented and nondemented subjects. Based on the "feature-integration-theory" of Treisman an experiment was designed in order to investigate more complex cognitive processes. The results showed that both P300-latency and RT may be used as additional diagnostic indices for cognitive capability.

The foreperiod of a motor reaction to an impending stimulus is accompanied by a slow negative wave of the event-related potential, the "contingent negative variation" (CNV), when the imperative stimulus follows at a fixed interval to a warning stimulus. Using similar experimental paradigms, an event-related desynchronization (ERD) in the alpha range occurs indicating cortical activation before and during motor acts. Both EEG-parameters were quantified for four subjects using the following experimental design: One second after a non-informative warning signal (WS) a cue was presented that indicated by which hand the subject had to respond quickly after presentation of a reaction stimulus (RS); subjects were requested to respond by pressing a button with their left or right thumb. EEG-signals were recorded unipolarly from 17 electrodes. Average ERPs and ERD were computed for all electrode sites for trials with left and right hand movements, respectively, and topographically displayed in simultaneous amplitude and ERD-maps. CNV and ERD could be observed simultaneously over similar brain regions, namely central over the motor cortex, frontal with possible location over the supplementary motor area (SMA) and also covering the parietal region. While the CNV had a interindividually different and wide distribution, the ERD calculated for the upper alpha band mapped focally over the electrode sites C3 and C4 overlaying primary sensorimotor structures, with a contralateral dominance. In contrast to the negativity which is terminated following delivery of the response stimulus, the ERD persisted during the motor reaction showing a similar pattern some hundreds of milliseconds before and after movement onset.(ABSTRACT TRUNCATED AT 250 WORDS)

Brainstem auditory evoked potentials (BAEP) were performed in a total of 20 subjects (mean age 33.2 +/- 15.1 years; severe head injury in most cases) with the diagnosis of coma dépassé. The control group consisted of 33 healthy volunteers (mean age 26.9 +/- 5.3 years). The presence, latency and amplitude of the single BAEP-components and the variations of the stimulus artifact were evaluated. The mean amplitudes of the stimulus artifact of the brain dead subjects were calculated (means +/- SD) to be 0.26 +/- 0.12 microV (control group: 0.11 +/- 0.03 microV). Pathological alterations of the mechanics of the inner ear as well as extracerebral changes in conductivity or stimulus related depolarization processes in extracerebral parts of the auditory system were taken into consideration to be possible reasons for this significant (p less than 0.001; t-test) difference.

Parkinsonian patients sometimes have problems to produce really fast motor responses. Often, these are significantly delayed in comparison to those of normal controls. In patients with tremor-at-rest, this delay might be induced by some attraction of the movement execution to the tremor oscillator, according to a hypothesis of Hallet et al. (1977). This study now examined the phase relationship between the on-going tremor and the onset of fast voluntary contractions in Parkinson's disease (PD), quantitatively. Five patients with prominent tremor-at-rest performed rapid isometric index finger abductions under self paced (SP) and reaction time (RT) conditions, and force and surface EMG signals from the FDI muscle were analyzed. In both conditions the SP and the RT, data showed that the onset of the contraction mostly occurs during the descending phase of the tremor oscillation and, accordingly, the phasic EMG burst synchronously with the tremor bursts confirming the above mentioned hypothesis.

This retrospective study comprises 34 patients, who died due to the cerebral damage caused by severe anoxia, who were assessed by EEG and AEP or SEP on the same day and in whom at least one of these electrophysiological methods indicated a fatal prognosis. EEG-findings identified 76% of patients with fatal outcome, whereas SEP reliably predicted the outcome in 93% of patients, who died of the cerebral anoxia. In some patients centrally acting drugs made EEG-based but not SEP-based prognosis impossible. In some cases of fatal brain damage, however, only the EEG-findings as opposed to SEP-findings predicted the fatal outcome. Thus the combined assessment by EEG and SEP appears to be optimal in the assessment of an early prognosis. The BAEP were of less prognostic value than the EEG. BAEP findings indicating a fatal outcome were to be found mainly in final clinical stages with loss of brainstem function, whereas EEG as well as SEP identified a considerable number of fatal cases in spite of comparably favourable clinical findings. The evaluation of early electrophysiological testing done within the first 3 days after the anoxic event results in an identical estimation of the prognostic significance of EEG versus BAEP- or SEP-findings, respectively.

One of the most interesting problems in EEG analysis is the question of the genuine generator of these biosignals. Each spontaneous EEG sampled by surface electrodes looks like a summary of stochastically distributed encephalo-electrical events. But analysing these data depending of the time distance of ECG R-waves we found signals which contain the information about the occurrence of the next ECG R-wave. The results make dubious the discussion about the autonomic character of sinus excitation as the heart pacemaker.

We investigated the spatial distribution of the sural nerve sensory nerve action potential (SNAP) in 25 healthy subjects between 21 and 50 years. Stimulation was achieved through surface electrodes at the lateral malleolus. Recordings were made 15-18 cm proximal to the site of the stimulation from different positions on a line perpendicular to the sural nerve using needle electrodes insulated except for the tip. The amplitude of the SNAP decreased on both sides of the potential of highest amplitude. 10 mm lateral to the potential of highest amplitude the mean amplitude was reduced to 55%. The latency of the first positive phase decreased within increasing distance from the largest SNAP. We explained this with different influence of more distal, earlier depolarized nerve segments on the locally generated SNAP. In 20 subjects we performed an additional recording using an uninsulated needle electrode that was placed 3-4 cm subcutaneously perpendicular to the sural nerve. The latency of the SNAP recorded in this way was similar to the latency of the largest SNAP using the insulated needle electrode; however, the amplitude was smaller by 19%. We recommend for clinical practice to use the uninsulated needle in case the SNAP is smaller than 4 microV.