Event-related brain potentials were recorded in a group of German-speaking (n = 12) and a group of English-speaking subjects (n = 12) while they read sentences containing relative clauses in their respective mother language. These relative clauses were manipulated such that in half of the sentences the subject of the main clause was also the subject of the relative clause, while in the other half it served as the object of the relative clause. ERPs were recorded from 32 channels and were analysed on the word and the sentence level. On the word level the results of the English group replicated the study by King and Kutos [7] with differences at all positions following the relative pronoun. However, the comparision to the German study, which did not reveal any consistent differences, suggests that word-class differences due to the rearrangement of the word-order in the two sentence types was the reason for the differences. On the sentence level, an extended negativity was found onsetting at word 3 of the relative clause for the object-relative clauses in both languages. This is a likely correlate of the different working memory loads posed by the two sentence types. The investigation underscores the utility of sentence level ERPs.
We examined 73 patients on artificial respirators between 2 to 168 hours after cardiopulmonary resuscitation. During that time period, bilateral Medianus SEPs were obtained according to standardized conditions. At the end of the observation period, the neurological outcome was determined and correlated with the obtained SEP results. Statistically significant correlations (p < 0.001) were found for the central conduction time and the amplitude of the N-20 as well as of the P-25 peaks. All patients with no cortical activity either suffered brain death (N=4) or died in a persistant vegetative state (N=6). Patients with pathologically reduced N-20 peaks <0,5 mu V (N=11)also died in a persistant vegetative state. This study emphasizes the value of medianus-SEP diagnostics in the area of neurological, intensive medical care and demonstrates that the proof of a cortical "flat line" during hypoxic coma is coupled with a fatal prognosis. The proof of inconspicuous cortical primary potentials by itself does not always entail a positive prognosis.
Normative data are presented for a standardized transcranial magnetic motor cortex stimulation (focal eightshaped coil, antero-posterior coil currents, 80% of maximal stimulator output, maximal tonic contraction of hand muscles) for different callosally and corticospinally mediated electromyographic effects in the first dorsal interosseus muscle. The data shall serve as a basis for a more widespread use of magnetic cortex stimulation to investigate the function of callosal motor fibres. Parameters of callosally mediated inhibitory effects are the onset latency and duration of transcallosal inhibition and the transcallosal latency time. No significant side differences were found for any of the different parameters, Parameters of corticospinally mediated effects which originate from the same motor cortical area are response threshold, onset latency, central and peripheral latency and the amplitude of excitatory electromyographic responses in contralateral muscles, The duration of postexcitatory inhibition in contralateral muscles is also given as an inhibitory carticospinally mediated effect.
Immunological changes have been stated as one factor in the development of painful radiculopathies. The aim of this study was to determine the effect of cytokineinhibitors on the electrophysiological changes seen in experimentally autoimmune damaged lumbar nerve roots. 18 inbred female Lewis rats were sensitized with homogenates of the peripheral nervous system. Experimental allergic radiculitis (EAR) was triggered by inoculation with 3 mg myelin in 150 mu l normal saline with an equal volume of complete Freund's adjuvant containing 20 mg/ml Mycobacterium tuberculosis. Rats were treated either with Interleukin-1 Receptor Anatagonist Protein, either with high dose prednisolone, or saline injections. For neurophysiological evaluation evoked potential technique was performed. One week after injection controll-animals developed clear clinical and neurophysiological symptoms. The antiinflammatory effect of prednisolone was higher compared to IL- 1 ra, but antiinflammatory effect of IL-l ra was still significantly higher compared to controlls (Fig. 1,2). Our results indicate that IL- 1 plays a role in lumbar radiculitis. Our results also show that cytokineinhibitors have a benefical effect on the clinical and neurophysiological parameters of experimental radiculitis. This is of major importance since there are several natural substances known, which inhibit cytokine effects in vitro. Furthermore regarding efficiency and side effects a genetherapeutical approach is of interest.
The clinical picture of salicylate-poisoning is characterized by neurological symptoms reaching from mental slowing, confusion, hallucinations to convulsions, We describe a patient, who showed EEG abnormalities in the form of mild diffuse slowing with additional intermittent slow activity on repeated admissions, These abnormalities rapidly disappeared together with the clinical symptoms of mental slowing, ataxia, dysarthria and confusion. Eventually, a chronic salicylate intoxication was revealed. It is suggesed that EEG abnormalities serve as an additional diagnostic clue in this potentially fatal condition.
Several techniques based on electromyography have been developed to assist the diagnosis and monitoring of movement disorders. Long-latency reflexes (LLR) of hand muscles show a rack of the transcortical reflex in case of lesions within the central transcortical pathway and in Huntington's Disease. Enhanced LLR are found in some movement disorders and are helpful for the differential diagnosis of akinetic-rigid syndromes and the differential diagnosis of myoclonus. Brainstem reflex testing is useful for the diagnosis of lesions within the brainstem or cranial nerves. Paired stimulation techniques allow the evaluation of central excitability of brainstem pathways. The measurement of ephaptic late responses between branches of the facial nerve is the ultimate diagnostic confirmation for hemifacial spasm. Polymyography is a useful tool for the differential diagnosis of ties and myoclonus. It is mandatory for the diagnosis of orthostatic tremor and asterixis and it is sometimes useful for the differential diagnosis of other tremors. Polymyography is meanwhile frequently used to guide the treatment with botulinumtoxin and to monitor the muscles to be injected. This is an important extension of electrophysiological techniques from diagnostic procedures into therapeutic applications.
The BMRC-Scale is most common used to estimate the degree of paresis in clinical routine. However, quantification of muscle strength is crude and detection of discrete paresis and minor changes in the course of the disease are difficult. Therefore we introduced the twitch-interpolation technique to measure peripheral and central paresis in the clinical setting. The method involves the interpolation of electrical elicited twitches on a maintained voluntary contraction (VC). During truly maximal VC no extra force is generated. Residual twitches despite of maximal effort by the patient reveal the inability to recruit all motor units available. The isometric VC is continuously recorded by a dynamometer. After determination of the maximal VC (MVC) patients are instructed to keep their muscle farce at a level specified by a horizontal line on the display of the dynamometer. Subsequently, three electrical stimuli are applied at each level of VC. The changes in twitch parameters at different levels of muscle activation provide information about the extend of motor unit recruitment. In addition to the measurement of the maximal muscle force, the method allows the prediction of true maximal force (TMF) based on the known observation of a linear relationship between decrement in twitch force and increased voluntary force. In patients with central paresis even slight dysfunction is detected by residual twitches. In myopathic diseases the use of the available motoneuron pool can be estimated. Finally the method is recommended to report central and peripheral paresis in patients with amyotrophic lateral sclerosis.
The Austrain Society of EEG arose out of a working group of austrian electroencephalographers. A working association was founded on september 11, 1954 at Bad Ischl during their first meeting in time-relation to the congress of austrian and german neurorurgeons. This working association was conforming to law transformed into a regular society on october 12, 1956 by the motion of the three proponents Hoff, Rohrocher and Bertha. Faithfully adhering to the regulations the society has since regularly held each year at least one annual meeting, often additional spring or autumn meetings, or meetings with neighbouring societies. In 1959 the organization in Badgastein of the first Alpine EEC Meeting, also called "Alpine EEG Ski Meeting" initiated regular cycles of similar annual meetings with Italy, Germany, Switzerland, and France. The evolution of electroencephalography necessitated four amendments of the statutes during the following decades. These included an increase in the number of officers, changes in rules for admission of new members in particular fields of specialities, and the change in the name of the society. This last change perticularly reflects the transition from ancient "Elektrenkephalographie" to modern clinical Neurophysiology. Reviewing all the dates of the austrian EEG history it is clear, that the steep increase in development of policy, organisation, and research was similar to the increase in other european EEG-societies. However, on can see differences in three different fields to other european EEG-societies: - The political situation enables and commits the Austrian EEC-society to offer more options for communication to the eastern and southern neighbours. - The organisation of austrian rules for admission may serve to other european EEG-societies as a model for improvement of quality in the practice of EEG-routine. - In EEG-research the traditional austrian connection with psychology can open a better approach to the problems of psychiatry when based on studies.
Development of force in a muscle occurs via activation of new motor units and by an increase of their firing rates. The electrical activity increases in parallel, because both depend on the number and cross sectional area of activated muscle fibers. Force is futhermore influenced by the metabolic profile of the motor units and by mechanical properties like the initial length of the muscle fibers. Similarly the potential size is determined by the spatial distribution of the fibers within the territory of a motor unit and their orientation to the recording electrode, by the degree of synchronisation, and by the characteristics of the recording technique. The slope of the relationship between force and emg varies physiologically with muscle, species, level of activation and the applied technique. The frequency spectrum, interference analysis and recruitment pattern at a given activation level can preferentially be studied in a whole muscle. Intramuscular microstimulation or the spike triggered averaging method produces contractions of single motor units. The combination with macro emg allows to characterize their electromechanical relationship.
The introduction of transcranial magnetic stimulation has allowed the study of motor functions in lesions of the central nervous system. Pathological central motor conduction times, amplitudes or threshold stimulus intensities have been found in multiple sclerosis, amyotrophic lateral sclerosis, cervical myelopathy and other neurological disorders. Therefore, these parameters are widely used as a diagnostic tool for clinical questions. Some theoretical aspects are also reviewed. They include 1. physiological and pathophysiological function of the corticospinal system investigated with single motor unit studies in healthy subjects and patients with disorders of the central nervous system and 2. spinal and supraspinal excitatory and inhibitory actions.
New techniques permit to study quantitatively action potentials of the motor unit at the single fibre level and at large. With new needle designs, EMC-machines and software it is today also possible to do single fibre-EMG and macro-EMC recordings in all EMC laboratories. Yet, these techniques are usually restricted to solve problems in specific situations. The knowledge of details on recording, technical pitfalls and anatomy, which are discussed here, provide a better and modern understanding of the dynamic changes within the motor unit in its healthy and diseased state.
Oscillatory patterns of electrical activity of nerve cells, well known in the EEC, have recently been observed at the cellular level as well. Measurements of event-related potentials permit, when analyzed in the frequency domain, to measure - in the EEG - oscillations in temporal relation to events. As numerous investigations show, such event-related oscillations have different functional correlates (according to their respective frequencies). With respect to gamma oscillations (30-80 Ht), for example, these investigations indicate a wide spectrum of functional correlates, ranging from primary sensory to cognitive processing (for alpha oscillations, see 72).
With transcranial magnetic stimulation it is possible to stimulate areas in the human brain through the intact skull. In order to influence the speech associated areas during speech production we applied single magnetic stimuli over the left and over the right hemisphere. Healthy right-handed volunteers were asked to read single words as soon as they appear on a computer screen. 120 ms after the presentation of each word, a magnetic stimulus of 1 tesla was applied over the fronto-temporal region. Latency of the verbal reaction and frequency of paraphasias were documented via a microphone-oscilloscope-array. We found no significant speech impairment with single pulses in contrast to repetitive stimulation of the speech associated areas. We assume that polytopic information processing of the "young" brain functions like speech production may contribute to the relative stability against brief electromagnetic impairment.
We performed a Median nerve SEP monitoring on six comatose patients with global cerebral hypoxia after cardiopulmonary resuscitation (kardiopulmonale Reanimation). The purpose of the study was to determine the exact recovery time of the scalp recorded potentials after circulation had stopped. The recordings began 90-180 minuts after kardiopulmonale Reanimation. One patient had an isoelectric SEP at the beginning and during the time period and died after 24 hours with the clinical signs of brain death. In five patients the N20 peak initially was well defined and showed an increase in amplitude of 11,8 % (2-25 %) within 12 and 24 hours. The P25 peak initially also was well defined, but showed an increase in amplitude of 110 % (50 -185 %), and stabilized after about 12 hours. The amplitudes of the N35 peak increased by 218% (60 -464%). The potentials of medium and late latency (P45 and N70 peak) were initially absent in all five patients, but were noticed for the first time 3,5 to 9 hours after onset of the hypoxia. The recovery time of the somatosensory evoked cortical potentials (SEP) by Median nerve stimulation after global cerebral hypoxia can therefore be determined to last about 12 hours.
Repetitive transcranial magnetic stimulation (rTMS) of the brain is a new tool with an expanding range of applications, In this overview, stimulation of the motor cortex is used as a model for an analysis of the transcranially activated cortical mechanisms. The following motor effects of rTMS are analyzed: increment of stimulation effects, afterdischarges of emg-responses, flip-flop of excitatory and inhibitory stimulation effects, cortical stimulus spread. Long term depression (LTD) and long term potentiation (LTP) of cortical excitability may be associated with probable therapeutic effects of rTMS in epilepsy or Parkinson's disease while the basis of beneficial effects in depression is still unknown. The observed changes of cerebral perfusion are associated with neuronal activation. The interference of rTMS with complex brain functions such as speech may be used to detect the speech-competent hemisphere. To elicit an epiletic fit is considered to be the main risk of rTMS, It can be reduced by choosing combinations of stimulus parameters (frequency, intensity, train duration, inter-train-interval, number of trains) within defined limits.
To assess corticospinal tract function in multiple sclerosis, the effect of transcranial magnetic cortex stimulation (TMS) on discharge characteristics of single motor units (SMU) was investigated. SMU-discharges in relaxed hand muscles were evaluated by post-stimulus-time-histograms (PSTH, bin width: 0.2 ms, concentric needle recordings). TMS was performed with threshold intensities. The SMUs activated by TMS in the relaxed muscles were also the first being recruited during slight tonic contraction in the patients and normal subjects. In comparison to normals (12 SMUs), the patients (9 SMUs) showed a higher cortical excitation threshold for the activation of SMUs (59.7 vs. 40.8% of maximal stimulator output), a prolonged latency of the first (36.7 vs. 27.0 ms) and the second discharge peak in the PSTH (42.2 vs. 27.8 ms) and a prolonged inter-peak-interval between these two peaks (2.4 vs. 1.5 ms) whereas the average number of peaks was the same in normal subjects and patients (1.4 peaks). The results hint at an impaired transcranial activation of even the best voluntarily activated SMUs. However, the observed changes of temporo-spatial summation of transcranially elicited descending excitation in multiple sclerosis were not specific when compared with the findings of different authors in other diseases of corticospinal tract neurons.
There is a strong correlation between structural and neurophysiological findings in a wide variety of neuropathies if appropriate sets of diagnostic procedures are employed. Etiologic considerations heavily rely on the dissection of axonal damage and demyelination. Histologically, the work-up of a nerve biopsy should not only focus on transverse sections but should also include teased fibre studies and electron microscopy. Particular emphasis should be put on axon-myelin junctions at paranodal regions. Although critically involved in generating gross neurophysiological nerve dysfunction in primary as well as secondary demyelination, paranodes have long been neglected by morphologists. Neurophysiological studies in patients with neuropathy should be performed as early as possible and repeated in the course of the disease. Routine nerve conduction techniques must be complemented by F-wave studies and by a careful assessment of compound action potential amplitudes. Serial studies not only give a comprehensive view of the current status of nerve function but also provide a valuable prognostic means. There are some pitfalls, however: The diagnosis of nerve conduction block must not be made without taking innervation abnormalities into account and without ensuring supramaximal stimulation. In the first two weeks of inflammatory neuropathies, a very distal conduction block has to be considered if compound muscle action potential amplitudes are low in the absence of denervation potentials in the electromyogram.
EEG mapping and diagrams which reflect the maximum amount of information in a comprehensive overview are generally the most popular and widely-used methods of representation in clinical routine EEG evaluations. The introduction of the analog digital transformation means that it is now possible to reduce the relevant data quantity to single graphic image, in the form of an EEG map, even when there are a large number of channels to be considered. However, this article contains references to the necessity of employing decision aids which determine very clearly-defined contraints. On the basis of a clinical test involving 18 brain infarcted patients, this study shows that doctors who employ the Z Model are provided with a clearly comprehensible and statistically perfect device which can determine whether the patient deviates significantly from a norm group. By means of a control sample, Power Group values were calculated for four frequency bands (alpha 1, alpha 2, theta, delta) in a subsequent stage (Z Model) the values measured for each brain infarcted patient were compared with the values measured for the control group. In this way, the Z Model directly indicates the points where a patient shows significant deviations from the control group.
Stimulation of the ear by loud elicits evokes a potential which can be averaged out of the EMG-activity from contracted sternocleidomastoid muscle. This phenomenon has been called vestibulo-collic reflex because of a presumed disynaptic pathway from the vestibular organ via the vestibular nuclei to the motoneurons of cervical muscles. In order to test this suggested pathway, we examined the vestibulo-collic reflex in 20 healthy volunteers and seven patients with topologically defined lesions of the brain stem (four patients with Wallenberg's syndrome of the dorsolateral medulla, one patient with a lesion in mesencephalon and two patients with tumors in the cerebello-pontine angle). Clicks were delivered unilaterally via a pair of headphones. EMC activity was collected over 100 ms by surface electrodes placed on sternocleidomastoid belly and averaged. Muscle was maintained in tonic contraction during the examination by elevation of the head. In the healthy subjects, a biphasic potential with initial positive deflection and short latency could be recorded on the side of the stimulation (fig. 2). In the two patients with tumors in the cerebello-pontine-angle and in two patients with Wallenberg's syndrome, the potential was abolished on the affected side (fig. 4). One of these patients, who showed a loss of the potential four days after the stroke, was examined a second time fifteen days later, and now the reflex had reappeared. In the other two patients with Wallenberg's syndrome, the reflex was normal. But in these two persons, the ischemic lesion was already older (>10 days). Our results support the suggested pathway of the vestibulocollic reflex from the vestibular nuclei to the motoneurons of the sternocleidomastoid muscle in the dorsolateral medulla.
Urinary stress incontinence after radical prostatectomy could be cured by physiotherapy in a high percentage. We developed an investigation procedure for description of myoelectrical activity of pelvic floor with 8 surface electrodes (4-channel, bipolar montage). Ten patients were studied one day before, ten days and six months after radical prostatectomy. Significant changes of amplitude and frequency characteristics could not be found in rest and during the stationary intervals of maximal contraction. But after the operation in all patients changed the activation pattern within the interval of increasing muscle contraction. The mean and median frequency decreased (Friedman-test, p<0.001). Changes were interpreted as a problem of intramuscular coordination. After physiotherapy urinary incontinence was cured or improved. The typical activation pattern of dyscoordination was not more evident after six months.
