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Biomedical subjects

L Deecke

Publications and source records attributed to L Deecke.

At least 163 records · Page 9Linked to original sources
PubMed1991

[Sleep and epilepsy].

The frequency of epileptiform discharges shows a wide intraindividual variability; it is influenced by the sleep-waking cycle and by the different stages of sleep: generalized seizures (tonic-clonic, tonic and myoclonic) are activated in nonrapid eye movement sleep, partial seizures tend to have more complex relationships with sleep states. Generally, sleep stages I and II and transit stages have an activating effect on discharges. Rapid eye movement sleep has an "anticonvulsive" effect and focalizes paroxysmal activity. Sleep recordings are useful for localizing a focus in temporal lobe seizures and for differentiation of epileptic seizures from non-epileptic seizure-like sleep disturbances. EEG after sleep deprivation should be used in patients suspected of suffering from epilepsy whose prior EEGs (including hyperventilation, photic stimulation and short sleep) were normal or yielded borderline abnormalities. Epileptiform discharges can--without clinical seizures--produce arousal reactions and sleep disturbances.

Cerebral Cortex↗
PubMed1991

[Age and whole blood viscoelasticity. A risk factor study].

To assess whether the viscoelastic properties of whole blood might be influenced by age, we measured viscoelasticity of whole blood (VEWB) and plasma at different shear rates in 84 healthy adult subjects. Additionally, we examined the relations between VEWB and gender, cigarette smoking, and oral contraceptive use. VEWB (shear rates 10/s and 50/s, adjusted to a haematocrit of 45%), viscosity of plasma (shear rate 10/s), aggregation index, shear resistance and flexibility index of erythrocytes were measured with an oscillating capillary rheometer and densitymeter. By means of univariate analysis, age was found to increase whole blood elasticity at low shear rates and shear resistance of erythrocytes. Concerning high shear rates, this relationship could only be established in males. The rheologic values of women who had taken oral contraceptives for at least one year were not related to age. Multiple regression analysis demonstrated that whole blood elasticity at low shear rates and shear resistance of erythrocytes were significantly related to age and the intake of oral contraceptives. On the contrary, there was no relationship between age and whole blood and plasma viscosity as well as aggregation and flexibility indices.

Adolescent↗
PubMed1991

[Therapeutic possibilities in spasmodic torticollis].

Spasmodic torticollis is classified as a focal dystonia. It is characterized by involuntary contractions of the muscles of the neck, with consequent deviation of the head from the correct posture. Psychological factors are recognized as important trigger and aggravating mechanisms. The various possibilities of therapeutic management (medical and surgical treatment, psychological methods and psychotherapy) are reviewed. Therapy of spasmodic torticollis should be started with methods such as biofeedback, behaviour therapy, and anticholinergic drugs. If these procedures not successful, local application of botulinum toxin offers a new and highly effective technique. Surgical treatment such as neurotomy, rhizotomy, or stereotaxic operations should be restricted to otherwise intractable cases.

Accessory Nerve↗
PubMed1990

[24-hour blood pressure determination in Shy-Drager syndrome. A case report].

The case history is presented of a 57 year-old male patient suffering from the Shy-Drager syndrome. This syndrome was first described by G. M. Shy and G. A. Drager in 1960. The clinical manifestations are extrapyramidal, with Parkinsonian features, combined with severe orthostatic hypotension and failure of the autonomic nervous system. Apart from the standard clinical investigations in this condition, namely the orthostasis test and polygraphic recording of the EEG, ECG, breathing and blood pressure on the tilting table, additional non-invasive long-term determination of the blood pressure was carried out. This method allows simultaneous measurement of blood pressure and heart rate without appreciably interfering with the patient's daily activities.

Autonomic Nervous System↗
PubMed1990

Supplementary motor area activation while tapping bimanually different rhythms in musicians.

In 15 musicians, cortical DC-potentials were recorded from the scalp before and during the execution of bimanual motor sequences. Subjects (Ss) either tapped with their two index fingers in synchrony (quavers against quavers; "2 against 2") or they tapped quavers against triplets ("2 against 3"). Either the right or the left finger started tapping the quavers (onset time t1), after about 4 s the other finger joined in (t2) either with quavers as well (easy rhythm) or with triplets (difficult rhythm). Ss were free to start the sequences, i.e. to determine the onset times t1 and t2. Shifts of cortical DC potentials were averaged twice; (1) time-locked to t1 and (2) time-locked to t2. When moving in synchrony (easy rhythm) DC-potential shifts and maps of radial current densities across the scalp indicated activations of the two primary motor cortices (MI). When bimanually tapping different rhythms, there was not only an activation of MI cortices, but in addition a very large activation of the mesial, central cortex was observed. It is suggested that this cortical area which mainly contains the supplementary motor area (SMA) has the function of controlling the initiations of movements in the difficult sequence which have to fit into a very precise timing plan. Interestingly, activation of the mesial, central cortex preceded the actual performance of the difficult rhythm by about 4 s. This finding indicates that the preparatory set differs between the two tasks.

Adult↗
PubMed1990

Magnetoencephalography in clinical epileptology and epilepsy research.

This article reviews the application of magnetoencephalography (MEG) in clinical epileptology and epilepsy research. MEG recordings of interictal as well as ictal epileptiform discharges helped to improve non-invasive localization of epileptic foci in patients with focal epilepsy. Several studies showed good agreement of the localizations obtained from MEG compared with those from invasive electrical recordings. Thus, MEG may become a potentially useful technique in the pre-surgical evaluation of epilepsy patients. As evidenced from studying the penicillin focus in animals and spike propagation in humans, MEG also may contribute to further understand the basic mechanisms of epilepsy and thus may be useful in epilepsy research. Directions of future research include recording from a large number of channels covering a wide area of the head, long-term recording to study mechanisms involved in the transition of interictal to ictal state, and recording of slow magnetic field shifts associated with interictal and ictal epileptiform discharges.

Epilepsy↗
PubMed1990

Movement-related potentials accompanying unilateral and bilateral finger movements with different inertial loads.

The present study was aimed at investigating the effect of inertial loading on movement-related potentials (MRPs) recorded from the scalps of normal subjects while performing finger movements. Two experiments were performed. Experiment 1. MRPs preceding and accompanying the execution of voluntary, unilateral finger movements were investigated in 8 subjects under the 3 experimental conditions of: no inertial load, small inertial load (250 g), and large inertial load (400 g). A significant effect of the inertial load on Bereitschaftspotential (BP) amplitude was observed for the 100 msec period preceding movement onset (BP -100 to 0) at precentral electrode sites and following movement onset (N0 to 100) at both precentral and parietal electrode sites. Pairwise comparisons revealed that significant effects were due to differences between the loading and non-loading conditions and not for different amounts of loading. No significant differences were observed for BP onset or early BP amplitudes, indicating that scalp negativity immediately prior to, and during, movement onset is primarily influenced by conditions of inertial loading. Experiment 2. This experiment examined the effect of inertial loading on MRPs for bilateral, simultaneous voluntary finger movements in 10 subjects under conditions of: no inertial load, inertial load applied separately to the left and right fingers, and with identical inertial loads applied to both fingers. No significant effect of inertial load on MRP amplitude was observed. These results are contrasted with those of experiment 1 which show significant effects of inertial loading for unilateral movements and are interpreted in terms of the hypothesis that bilateral movement organization involves 'higher' aspects of motor control than those reflecting adjustment to conditions of inertial loading.

Adult↗
PubMed1990

Cerebral correlates of imagining colours, faces and a map--II. Negative cortical DC potentials.

Cortical activation patterns as measured by negative shifts of the scalp-recorded cortical steady potential ("DC shifts") were assessed in 28 normal subjects during imagining colours, faces, and a spatial map. Imaging resulted in sustained negative DC shifts at temporal, parietal and particularly at occipital sites. The topographic distributions of such DC shifts was modulated as a function of whether spatial or visual imagery was performed. During imaging the spatial map, a parietal maximum was observed, as opposed to a distribution in favour of temporal and occipital sites during imagining faces and colours. Results suggest a neuroanatomical dissociation between visual and spatial imagery. Since a similar visual-spatial dichotomy exists in perception, the finding is interpreted as further evidence of a shared cerebral substrate for images and percepts. The results are discussed in conjunction with the joint blood flow study.

Adult↗
PubMed1990

Elaborative strategies in word pair learning--DC-potential correlates of differential frontal and temporal lobe involvement.

Cortical DC potentials were recorded while subjects were learning word pairs. The use of an elaborative mnemonic strategy resulted in a left frontal sustained negative shift. Its amplitude was independent of whether imagery mnemonics or semantic mnemonics were used. By contrast, posterior temporal potentials differed according to strategy: with imagery mnemonics, subjects had more symmetrical potentials over posterior temporal areas whereas with a semantic strategy, there was a left hemispheric preponderance of the DC potential. An interpretation within Stuss and Benson's theory on the frontal lobes is given.

Adult↗
PubMed1990

Negative cortical potentials when classifying familiar and unfamiliar faces.

Event-related potential (ERPs) were recorded while subjects were classifying familiar faces of celebrities according to profession in one task, or unfamiliar faces according to gender in another task. Familiar faces given rise to an enhancement of the late negative ERP component confined to parieto-occipital sites. The finding is considered to reflect parietal and occipital lobe involvement in the activation of memories pertinent to familiar faces. Moreover, the late negative component was more prominent over the right than the left occipital lobe.

Adult↗
PubMed1990

The influence of temperature on somatosensory-evoked potentials during cardiopulmonary bypass.

Somatosensory-evoked potentials (SEPs) after median nerve stimulation were recorded in 10 neurologically normal patients during cardiopulmonary bypass and hypothermia. In all patients the changes of the latencies (spinal N13, cortical N20 and N35) and the central conduction time during cooling, and the decrease in latencies during rewarming was described by a gamma function. The analytic discussion of pooled data of all patients led to another SEP-latency-temperature relationship than the observation of each single patient. In 6 of 10 patients there was found a maximum of latency increase before the minimal temperature was reached. The cooling and the rewarming curve had to be considered separately. Latency changes of SEPs during hypothermia are discussed as a very complex phenomenon influenced by many technical and patient factors. This reduces the value of SEPs as an index of central nervous system integrity during open heart surgery and hypothermia.

Adult↗
PubMed1990

[Possibilities and limitations of the automatic analysis of sleep stages using the Oxford system].

34 ambulatory polygraphic sleep-records of young adults were carried out using the Oxford Medilog 9000 recorder. All of the records underwent automatic evaluation by the Oxford Sleep Stager. 10 cases were, in addition, evaluated visually. 4 records could not be analyzed because of artifacts. Thus, 30 subjects were used in the end for establishing standard values of sleep parameters. Automatic versus automatic comparisons and automatic versus visual comparisons of ten polysomnograms were performed epoch-by-epoch. The automatic versus automatic comparison showed agreement in 85.5% of epochs, and the automatic versus visual comparison in 70.4% of epochs. The Sleep Stager showed the best agreement with the visual evaluation in epoch-by-epoch comparison in the REM-stage (93.9%), the worst in stage 1 (32.4%). In calculating the percentages of total night sleep for the respective sleep stages, the automatic analysis showed strongest disagreement with visual evaluation in the REM-stage (plus 7.5%) and in stage 2 (minus 5.2%).

Adult↗
PubMed1990

[The significance of EMG artefacts in isoelectric EEG].

Five potential organ donors showed muscle artefacts during isoelectrical EEG recording. The electromyographic examination revealed MUAP activity occurring as doublets, triplets and quadruplets. All patients had normal blood chemistry except reduced CO2 and increased O2 partial pressures. We assume that the recorded "tetaniform" muscle activity is due to hyperexcitability of the nerve membrane caused by artificial hyperventilation.

Adult↗
PubMed1990

Electrophysiological correlates of movement initiation.

By averaging the electroencephalogram (EEG) or the magnetoencephalogram (MEG) of waking man in a manner time-locked to the onset of self-initiated volitional acts, movement-related potentials (or magnetic fields) can be recorded. In the preparation period, a slowly increasing cortical negatively called the Bereitschaftspotential (BP) or readiness potential, can be recorded. The BP precedes all our self-initiated (i.e. endogenous or willed) movements and actions by 1 sec or more prior to the onset of muscular contraction. The BP has 2 principal components, an early one which is bihemispherically symmetric, even prior to unilateral movements, and a late one which is lateralized towards the contralateral hemisphere. We have provided evidence (which was confirmed by regional cerebral blood flow studies) that the principal cortical generator producing the early component is the so called supplementary motor area ("SMA"), whereas the late asymmetric (contralateral) component is generated by the primary (rolandic) motor area, MI. The early "SMA"-related BP component may have motivational, intentional or timing properties, while the late component is related to synaptic facilitation in the contralateral MI area in preparation for the final pyramidal tract volley. In motor learning, the frontal areas are activated in both DC-potential recordings and emission CT experiments. The complete role of the "SMA" is not yet clear. However, it obviously has to determine the right moment to start a movement including the timing of single movements in motor sequences. It is particularly strongly activated in bimanual tapping of difficult rhythms.

Electroencephalography↗
PubMed1990

Spontaneous subarachnoid hemorrhage. Prognostic factors for social readjustment.

Sixty-seven patients surviving spontaneous subarachnoid haemorrhage (SAH) have been followed up for 2-12 years (mean: 7 years) in order to determine prognostic factors concerning the long-term disability in familial and social functioning. A correlation was found between the severity of the neurological deficit at the time of admission and the degree of familial and social disability at the end of the observation period. In addition, the Barthel-Index on discharge was shown to be of prognostic value for readjustment for social--but not for familial--functioning. Other clinical variables in the acute stage, however, including source of bleeding, sex, age, interval between SAH and admission, level of consciousness, cognitive functions, as well as initial Hunt and Hess grading and Glasgow Coma Scale scoring, did not influence the long-term social prognosis. Furthermore, residual neurological signs, cognitive dysfunctions, and the Glasgow Outcome score on discharge were not related to the extent of social handicap in the long-term outcome. At the end of the observation period, significant correlations were found between the presence of persisting neurological and cognitive deficits but also disability in ADL functions and occupational capacity and the decline in familial and social functioning.

Adolescent↗
PubMed1989

[Use of nicotine--a risk factor for stroke?].

The results of studies on cigarette smoking as a risk factor for stroke are more controversial than for cardiovascular disease. The CO-induced increase in the corpuscular elements of blood (erythrocytes), the influence on other parameters (such as RBC volume, haemoglobin, haematocrit, blood and plasma viscosity, tendency of erythrocytes and platelets to aggregate, fibrinogen level etc.), as well as the increase in catecholamine level are taken to be reversible. On the other hand, the association between cigarette smoking and probably irreversible morphological changes in the craniocervical vessels--possibly via lipid metabolism--is well documented. The following possible explanations for discrepant results in the literature are discussed: different extent of daily cigarette smoking, inhomogeneous populations, difficulties in diagnosing stroke, especially before the introduction of computed tomography and the common failure to consider other risk factors.

Cerebrovascular Disorders↗