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

The study was designed to examine the clinical applicability and use of computer-assisted EEG-analysis in comparison to visual EEG-analysis in patients with minor head injuries. For this in 31 patients the following examinations were performed within the first 24 hours, one, three and eight weeks after traumatization: EEG, neurological examination and standardized evaluation of subjective complaints. The EEG was analysed visually as well as computer-assisted. The results were compared to the neurological findings and subjective complaints. Reversible posttraumatic EEG-changes were observed in 50% of all patients. The results of computer-analysis and visual analysis were equivalent in respect to baseline-activity (as one of the main characteristic EEG-features). Furthermore, based on computer-assisted analysis a discriminant function is provided, which is of diagnostic and prognostic value in the single patient. We conclude that the computer-assisted EEG-analysis can be a useful alternative in EEG-routine diagnosis after minor head injuries.

In 20 healthy volunteers 16-channel surface electromyograms were monopolarly recorded from the right and left masseter muscle during defined functional conditions (force-constant bite, right and left hand side, 196, 333, 530 N chewing force, during a compensation of a load directed from a frontal or a lateral position to the mandible (20, 49, 69 N), during rest position of the mandible). The EMG curves were quantified by the calculation of spectral EMG-parameters (FFT). With respect to the muscle a topographic oriented representation of the myoelectrical activity was realised by a mapping of spectral EMG-parameters. The monopolarly recorded EMG activities significantly differed between the 16 electrode positions (topographic EMG distribution pattern). During the several examination conditions of the masseter muscle different topographic distribution pattern of the myoelectrical activity were found. Moreover, the total EMG power between the muscle functions differed too. The level of the load influenced the spectral EMG power as well as, partly, the topographic EMG distribution pattern.

A computerized EMG analysis system implemented on an MS-DOS computer was developed explicitly for clinical routine usage. It incorporates analysis of interference pattern as well as of motor unit action potentials (MUAPs). Key features of MUAP analysis are the automatic segmentation and parameterization of the EMG signal and the automatic assignment of MUAPs to motor units. Determination of muscle activity is based on threshold detection of the signal's first derivative, leading to the definition of a MUAPs central component. Its parameters (length, amplitude, maximal steepness, area between curve and base-line, area between first derivative and base-line, number of turns etc.) are used when comparing MUAPs. The automatic assignment of MUAPs to motor units was implemented as an iterative procedure. MUAPs are compared to a reference MUAP and eventually assigned to it if their parameters are sufficiently similar. For such a group of MUAPs the most representative MUAP is determined which is then used as new reference MUAP in the next iteration step. Most important for clinical routine usage are simple handling, speed and the clearly arranged presentation of results. The system allows for interactive modification of MUAP assignment as well as start and end points of every MUAP. Analysis results may be displayed on the screen and printed, giving the user a quick impression of the muscle under study. Thus this method meets basic requirements for computer assisted decision making in differential diagnosis.

In 18 healthy persons aged 22-71 years and 17 patients suffering from clinically defined polyneuropathy the NCV of the sural nerve was measured both by antidromic technic recorded by surface electrodes and by orthodromic technique recorded by needle electrodes. Stimulation was done by bipolar surface electrodes in all cases. The skin temperature was warmed up to the minimum of 35 degrees C. The results showed in both groups a highly significant correlation of the NCV measured by antidromic and orthodromic technique. With increasing age the NCV decreased, but this was not significant. In all healthy persons sensory nerve potentials could be recorded with both techniques. In polyneuropathy missing of sensory potentials was higher in patients investigated by the antidromic technique than by orthodromic. For clinical practice measurement of NCV in sural nerve using antidromic technique should be preferred because of its simpler and faster achieving, its lower discomfort for the patient and avoiding risk of infection. However in case of missing nerve potentials, orthodromic investigation using needle electrodes for recording should be added.

In a randomized single-blind cross-over-design the effect of 15 g dextrose was investigated against placebo with 48 healthy subjects at two different days each. The quantitative pharmaco-EEG was recorded occipitocentral at the left side (O1-Cz) under vigilance controlled conditions and then under resting conditions (three minutes each). Having measured its baseline it was repeated six times every 20 minutes starting 10 minutes after the application of the substance. After the administration of dextrose a stabilization of vigilance could be seen in the EEG by the following differences of statistical significance (p < = 0.05) between dextrose and placebo under resting recording conditions: In the first control (14.-16. minute post) there was a significant decrease of the relative power in the delta and in the theta range combined with an increase of alpha 2. In the second control (34.-36. minute post) there was a significant decrease of relative power in the theta range and significant increase in the alpha 1 range. In the third control (54.-56. minute post) and later on no effects of dextrose were left in the pharmaco-EEG. The significant differences in the first and second control have to be interpreted as follows: After the administration of dextrose the level of vigilance was increased compared to the placebo group.

In this study we interpreted the electroencephalograms of 50 patients, all suffering from a cerebral infarction occurred in the circulation area of A. cerebri posterior with or without involvement of thalamic structures. The diagnosis was established by clinical findings and via CT-examinations. Besides the EEG-findings which always occurred in the occipital region we found alterations which exceeded the above mentioned posterior disorder of the brain function. In most cases these have been bilateral paroxysmal disorders projected into the temporal regions but lateralized to the region of the existing posterior infarction. If we had CT-examinations of cerebral infarctions in the circulation area of A. cerebri posterior without an involvement of thalamic structures, there was no projected activity which exceeded the posterior disorder in EEG. In all cases with the additional affection of thalamic structures in CT the bilateral paroxysmal EEG disorders into the temporal region were found.

A new method for quantitative characterization of myoelectrical masseter activity distribution by mapping of spectral EMG-parameters is described. The surface electromyograms of M. masseter were monopolarly recorded (16 channels). On the basis of registered EMG intervals (512 ms) the spectral EMG power of several frequency bands was calculated (Fast Fourier Transformation). The spectral EMG parameters between the 16 electrode positions were estimated by linear interpolation (4-nearest neighbours algorithm). Afterwards the spectral EMG parameters were fitted in a grey-tone or colour scale with 10 intervals. The so obtained EMG activity maps ("EMG-Maps") permit a quantitative-topographic characterization of myoelectrical masseter activity during different functional load procedures. The frequency range which is to consider in masseter surface-EMG investigations encloses frequencies between 15 and 500 Hz. The topography of EMG activation pattern of M. masseter is only described in a comprehensive manner when the electrode array consists of 16 electrodes and more. During defined motor tasks like clenching with controlled forces the reproducibility of EMG-Maps which respect to the topography of EMG activity pattern is very high. The absolute values of spectral EMG power as well as power changes of selected band ranges during clenching correlate to the extent of chewing forces.

It is still unknown why only few motor units (MUs) generate F-waves in response to supramaximal stimulation of a motor nerve. Therefore we investigated whether the F wave production might depend on MU-size. According to the size principle of Henneman we used the twitch force as indirect measure of MU-size. MU twitch force was determined applying the technique of intramuscular microstimulation of single motor axons. 127 MUs were analysed in 16 normal subjects. F-waves were observed in 35 MUs (27%). It was found that MUs of different sizes produced F-waves with approximately the same probability. Obviously size is not a relevant factor for the capability of a MU to produce F-waves. Only the few very large MUs of a pool may have an increased tendency to produce F-waves because four of five MUs with extremely large twitch forces (> 70 mN) generated F-waves.

EEG and somatosensory evoked potentials were recorded in anesthetized rats before and up to 24 h after 30 min of global forebrain ischemia. Before ischemia, SEP (sweep time 1000 ms) included primary (N25P50) components and late potentials of low amplitude. During ischemia, SEP and EEG were isoelectric. During postischemic recirculation SEP evoked by stimulation at 1.0 Hz remained severely suppressed for 24 h, although long-latency potentials (> 100 ms) recovered. Using a very low stimulation frequency of 0.1 Hz, late components strongly increased in amplitude and the overall evoked activity in the averaged post-stimulus-EEG reached 90% of control. These results demonstrate that the SEP evoked at very low stimulation frequency may serve as an early indicator of functional brain recovery after prolonged cerebro-circulatory arrest.

A coherent EEG-rhythm occurring in the 40 Hz range has been shown to correlate with cognitive processes of attention in a large number of studies. We intended to evaluate whether this frequency is of specific functional significance, and whether it may represent a rhythm of excitability for cognitive processes. The model of a rhythm of excitability assumes the 40 Hz-EEG to be a timer and organizer for information processing. Event-related potentials of 12 healthy normal subjects were recorded in an experiment of attention (auditory click stimulation). In order to evaluate whether the phases of the 40 Hz-EEG represent a rhythm of excitability, responses to stimuli having similar phases at the beginning of the stimulus were selected and averaged. An effect of the different 40 Hz-phases could not be demonstrated on the amplitude and latency of N100 and P200, components of the event-related potential associated with information processing. These findings suggest that a possible timer for cognitive processes of attention is not linked to the phases of the 40 Hz-surface-EEG.