Biomedical subjects

C Baumgartner

Publications and source records attributed to C Baumgartner.

At least 109 records · Page 6Linked to original sources

PubMed1992

Cortical sensory representation of the human hand: size of finger regions and nonoverlapping digit somatotopy.

Findings differ on cortical representation of fingers between human and animal studies, and on digit somatotopy among human studies. To resolve these differences, we mapped cortical sensory representation of each of the five digits and of median and ulnar nerves in three patients, using focal peripheral electrical shock stimuli. We compared locations and sizes of cortical regions among digits and nerves, using the model of a current dipole in a sphere applied to electrocorticography from subdural grids. Cortical representation was larger for the index finger than for the little finger and for the middle finger than for the ring finger, which are similar to findings in the monkey but different from Penfield's classic sensory homunculus. The thumb was larger than the middle finger, as in the homunculus. There was nonoverlapping somatotopy of all digits in each patient. These findings demonstrate a previously unrecognized similarity of cortical sensory organization of the fingers between humans and other primates.

Brain Mapping↗

PubMed1991

Human somatosensory cortical finger representation as studied by combined neuromagnetic and neuroelectric measurements.

We studied somatotopy of human hand somatosensory cortex using evoked responses recorded on magnetoencephalogram (MEG) and scalp-electroencephalogram (EEG) in conjunction with dipole modeling. We found a somatotopic arrangement of cortical digit representations with a sensory sequence from lateral inferior to medial superior in the anatomical order thumb, index finger, middle finger, ring finger, and little finger. MEG alone was able to reproduce this sensory sequence more accurately than scalp-EEG alone. However, the combined information provided by both techniques improved localization accuracy even further. As MEG and scalp-EEG are complementary and confirmatory techniques, this combined approach was useful to get more complete information on the functional organization of human hand somatosensory cortex.

Brain Mapping↗

PubMed1991

[Prognosis after transient ischemic attacks].

Transient ischemic attacks (TIAs) are reversible neurological deficits due to cerebral ischemia in a vascular territory lasting less than 24 hours, usually less than one hour. The natural course of TIAs is variable. One third of the patients suffer from a subsequent completed stroke with lasting disability, one third of the patients continues to experience TIAs and in one third no further symptoms are encountered. TIAs are a warning symptom of a generalized vascular process, myocardial infarction being the most common cause of mortality and ischemic brain infarction being the most common cause of morbidity. Clinical parameters--besides age--seem to be of minor prognostic relevance. Vascular risk factors should be evaluated in all TIA patients; especially, a cardiac work up including 2D-echocardiography and an exercise stress test should be performed. Duplex sonography of craniocervical vessels shows atherosclerotic lesions in a considerable proportion of patients with TIA; however, localization of these lesions does not always correspond to clinical symptomatology. Some angiographic features are of prognostic relevance. Computed tomography (CT) and magnetic resonance imaging (MRI) show ischemic lesions in a considerable proportion of patients, which connects TIAs directly to ischemic brain infarcts. The extent and localization of these lesions are of some prognostic relevance. Blow flow studies on single photon emission computed tomography (SPECT) and studies of brain metabolism on positron emission tomography (PET) are abnormal in many TIA patients for prolonged periods and also have some prognostic impact. TIA patients probably are a heterogeneous group with a common symptom. A detailed diagnostic work-up may have implications on a more specific and efficient therapy.

Aged↗

PubMed1991

[The significance of laboratory findings in long-term antiepileptic therapy].

A retrospective study of 316 patients (173 men, 143 women; mean age 39 [17-87] years) who had taken antiepileptics (phenytoin, phenobarbital, carbamazepine, valproic acid) for at least six months, was carried out to assess the biochemical and haematological changes in relation to the drug used, the therapeutic programme and the drug serum levels. The most frequent change was isolated elevation of gamma-GT (9-89% of cases depending on the drug), followed by elevation of alkaline phosphatase (16-44%). Increases in the transaminases GOT (4-13%) and GPT (4-19%) were infrequent and minor. Changes in the blood picture were very infrequent and never more than minimal. Correlation between all these changes and serum drug levels was poor (r less than 0.15). Correlations between drug serum level and dose were found in the case of phenobarbital (r = 0.6) and valproic acid (r = 0.5). There was hence no evidence of any clear connection between the biochemical findings and the serum concentrations of antiepileptic drugs or their-dosage. The results indicate that undue importance has previously been attached to routine checks of biochemical parameters; abnormal biochemical findings by themselves are not usually enough to necessitate changes in treatment. Determination of biochemical and haematological parameters is necessary only if there are clinical grounds for it such as suspicion of side effects, the occurrence of epileptic attacks despite therapy, or change from one drug to another.

Adolescent↗

PubMed1991

The influence of the presence of collaterals on restenoses after PTCA.

To assess the influence of collaterals on the long-term follow-up after successful percutaneous transluminal coronary arteriography (PTCA), 120 consecutive patients were studied. Of these, 104 (87%) had an adequate reangiogram and were included. At the time of PTCA the collaterals were estimated by a scoring system. In addition, the coronary wedge pressure was measured in 49 patients six months after PTCA, a follow-up angiogram was performed, and the patients were split up into a group with restenoses (stenosis greater than 50%), 34 patients (32.7%); and a group without restenoses (stenosis less than 50%), 70 patients (67.3%). A total of 35 patients (30.7%) had collaterals. A comparison between both groups showed no significant differences in clinical parameters (age, angina duration, vessel involvement, lipids, blood sugar, and blood pressure), and stenoses-related parameters (degree of stenoses, eccentricity, balloon size, inflation pressure, dissection, gradient after dilatation, and residual stenoses). Patients with collaterals had a significantly higher incidence of restenoses than those without collaterals (45.7% vs. 26.1%, p less than 0.05). Patients with wedge pressure of less than 45 mmHg (n = 30) had a significantly lower restenosis rate (23.3%) than patients with a coronary wedge pressure of greater than 45 mmHg (n = 19) (restenosis rate 52.6%). It is concluded that the presence of collaterals indicates a high restenosis rate after PTCA within 6 months.

Adult↗

PubMed1991

Neuromagnetic investigation of somatotopy of human hand somatosensory cortex.

In order to investigate functional topography of human hand somatosensory cortex we recorded somatosensory evoked fields (SEFs) on MEG during the first 40 ms after stimulation of median nerve, ulnar nerve, and the 5 digits. We applied dipole modeling to determine the three-dimensional cortical representations of different peripheral receptive fields. Median nerve and ulnar nerve SEFs exhibited the previously described N20 and P30 components with a magnetic field pattern emerging from the head superior and re-entering the head inferior for the N20 component; the magnetic field pattern of the P30 component was of reversed orientation. Reversals of field direction were oriented along the anterior-posterior axis. SEFs during digit stimulation showed analogous N22 and P32 components and similar magnetic field patterns. Reversals of field direction showed a shift from lateral inferior to medial superior for thumb to little finger. Dipole modeling yielded good fits at these peak latencies accounting for an average of 83% of the data variance. The cortical digit representations were arranged in an orderly somatotopic way from lateral inferior to medial superior in the sequence thumb, index finger, middle finger, ring finger, and little finger. Median nerve cortical representation was lateral inferior to that of ulnar nerve. Isofield maps and dipole locations for these components are consistent with neuronal activity in the posterior bank of central fissure corresponding to area 3b. We conclude that SEFs recorded on MEG in conjunction with source localization techniques are useful to investigate functional topography of human hand somatosensory cortex non-invasively.

Brain Mapping↗

PubMed1991

Functional anatomy of human hand sensorimotor cortex from spatiotemporal analysis of electrocorticography.

We measured chronic electrocorticography (ECoG) of sensorimotor cortex during contralateral median nerve stimulation in 6 patients with partial seizures evaluated for surgery. We analyzed the spatiotemporal structure of the somatosensory evoked response (SER) using multiple source modeling to investigate functional anatomy of its neuronal sources. Two dipole sources in postcentral gyrus explained the large majority of the first 60 msec of the SER, indicating a subregion of hand somatosensory cortex generating this activity. The source locations agreed with normal functional anatomy from cortical stimulations, intraoperative photographs, and postoperative neurological examinations after focal excisions. The time patterns of both sources were biphasic like the previously described N20-P30 and P25-N35 peaks. The spatiotemporal patterns of both sources overlapped. Spatiotemporal analysis with multiple dipole sources appears useful to determine the number, locations, and spatiotemporal field patterns of cortical regions active during peripheral somatosensory stimulation and reveals simplicity in the macroscopic functional anatomy of dynamic human sensorimotor cortex.

Adolescent↗

PubMed1991

Spatiotemporal modeling of cerebral evoked magnetic fields to median nerve stimulation.

We measured somatosensory evoked magnetic fields during median nerve stimulation in 6 normal subjects. We applied multiple dipole models to study the spatiotemporal structure of early somatosensory evoked magnetic fields (SEFs), as well as the number, 3-dimensional location and time activity of their underlying neuronal sources. Two dipole sources were necessary to model the first 40 msec of SEFs explaining 85% of the data variance. Source 1 was located deeper than source 2, showed primarily a tangential orientation, and accounted for a larger part of the variance; source 2 showed no consistent orientation across subjects. Both sources showed biphasic time activities corresponding to the previously described N20-P30 and P25-N35 components. Spatiotemporal modeling could identify sources which could not be modeled consistently above noise by single moving dipoles (P25 component), revealed small latency differences of the two sources in some subjects suggesting parallel activation of these sources, and allowed separation of sources overlapping considerably both in space and time. We conclude that spatiotemporal modeling of SEFs may be useful to study functional anatomy of human sensorimotor cortex non-invasively.

Electric Stimulation↗

PubMed1991

Vascular-specific expression of the bean GRP 1.8 gene is negatively regulated.

In French bean, the glycine-rich cell wall protein GRP 1.8 is specifically synthesized in the vascular tissue. To identify cis-acting sequences required for cell type-specific synthesis of GRP 1.8, expression patterns of fusion gene constructs were analyzed in transgenic tobacco. In these constructs, the uidA (beta-glucuronidase) gene was placed under control of 5' upstream deletions as well as internal deletions of the GRP 1.8 promoter. Four different cis-acting regulatory regions, SE1 and SE2 (stem elements), a negative regulatory element, and a root-specific element, were found to control the tissue-specific expression. Deletion of the negative regulatory element resulted in expression of the uidA gene in cell types other than vascular cells. The SE1 region was essential for expression in several cell types in the absence of further upstream regulatory sequences. Full-length promoters having insertions between the negative regulatory element and SE1 strongly expressed the gene in nonvascular cell types in stems and leaves. Thus, vascular-specific expression of the GRP 1.8 promoter is controlled by a complex set of positive and negative interactions between cis-acting regulatory regions. The disturbance of these interactions results in expression in additional cell types.

Base Sequence↗

PubMed1991

The sensitivity of transcranial cortical magnetic stimulation in detecting pyramidal tract lesions in clinically definite multiple sclerosis.

We determined central motor conduction time (CMCT) (motor cortex to root C-8 and motor cortex to root S-1) as well as the amplitude of the compound muscle action potentials in the hypothenar and the abductor hallucis muscles on both sides in 44 patients with definite MS. We compared the values with standards obtained from 86 healthy controls and correlated them with the degree of clinical deficit of the limbs examined. Thirty-nine patients (88.6%) showed a prolonged CMCT. By comparison, only 74.4% of patients had abnormal visual evoked potentials.

Action Potentials↗

PubMed1991

Serum concentrations of immunoglobulins and of antibody isotypes in bone marrow transplant recipients treated with high doses of polyspecific immunoglobulin or with cytomegalovirus hyperimmune globulin.

The kinetics of immunoglobulins (Ig) and antibodies were followed in 10 bone marrow transplant recipients who received either high doses (0.5 g/kg body weight) of polyspecific intravenous Ig (HD-IVIG) weekly or cytomegalovirus hyper-Ig (CMV-IVIG, 0.1 g/kg body weight) every 3 weeks. In the HD-IVIG group, the mean total IgG concentration more than tripled and similar significant increases were seen for IgG1 and IgG2. IgG antibodies to CMV showed a marked increase in the HD-IVIG and a less pronounced rise in the CMV-IVIG group. IgM antibodies to CMV were present initially or became detectable in five patients, unrelated to the IVIG preparation. HD-IVIG induced a significant increase of IgG antibodies to streptococcal group A carbohydrate (A-CHO) and to smooth strain lipopolysaccharides (LPS) but not of antibodies against lipid-A. When the Ig treatment was discontinued, levels of total IgG and of IgG antibody to CMV decreased with an apparent half-life of 30 days. Both IVIG preparations were well tolerated and had no negative feedback on total Ig and on specific antibody production or other antimicrobial defence mechanisms. In patient nos. 4 and 10 who developed severe graft-versus-host-disease, transient serum Ig peaks including several Ig isotypes appeared after day 14. In patient no. 10 this peak contained an IgG antibody to H. influenzae type b (Hib), and IgM antibodies to CMV, Hib, A-CHO and LPS. This study clearly shows that serum concentrations of Ig isotypes, subtypes and specific antibodies, depend on at least four factors: total amount and composition of Ig infused, consumption, catabolism and endogenous production.

Adult↗

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↗

PubMed1990

Laminar interactions in rat motor cortex during cyclical excitability changes of the penicillin focus.

Laminar interactions between neurons in rat motor cortex during cyclical seizure episodes in the penicillin focus were studied using a combination of current source-density (CSD) and principal component analysis (PCA), combined with computer-based physical modeling. These data suggest that all phases of cyclical seizure phenomena are produced by interactions between two distinct populations of neurons, the same neuronal circuits previously reported to give rise to the direct cortical response (DCR) and electrically evoked interictal penicillin spikes (EIIS). The first population consists of small pyramidal cells in the supragranular layer, and the second population consists of larger pyramidal cells in the infragranular layers with apical dendrites extending to the cortical surface. The supragranular cells serve as a trigger zone for initiating both spontaneous interictal spikes (IIS) and polyspike bursts (PSB) during seizures. Fast activity in the supragranular cells is typically followed by a hyperpolarizing slow wave that may be the result of Ca2+-activated K+ currents. This slow wave increases during seizures, possibly reflecting changes in extracellular Ca2+ associated with seizure onset and termination. The monophasic response of infragranular cells is similar for both IIS and PSB and consists of a large depolarizing shift followed by a rapid but partial repolarization period and a subsequent gradual repolarization period lasting several hundred milliseconds. The infragranular response is similar in polarity and morphology to the intracellularly recorded paroxysmal depolarization shift (PDS) and may indicate that these deeper neurons are mainly responsible for this phenomena in neocortex. Finally, there is a marked postictal slow oscillation between the supra- and infragranular layers. This oscillation appears first and largest in the supragranular cells and may reflect a disturbance in excitatory feedback in these cells produced by the disinhibitory effect of penicillin, a disturbance capable of pathologically synchronizing the epileptic neuronal aggregate sufficiently for activation of the spike-generating mechanism and subsequent seizures.

Animals↗

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

Laminar analysis of extracellular field potentials in rat vibrissa/barrel cortex.

1. A 16-channel electrode array was used to record simultaneously extracellular laminar field potentials evoked by displacement of contralateral vibrissa from vibrissa/barrel cortex in five rats. Current source-density (CSD) analysis combined with principal component analysis (PCA) was used to determine the time course of laminar-specific transmembrane currents during the evoked response. 2. The potential complex consisted of biphasic fast components followed by long-lasting slow waves. It began with activity in supragranular cells consisting of a source in layers I-II and a sink in layers IV-V; this was followed by activation of the infragranular cells with a paired sink and source in layers I-IV and V-VI, respectively. The slow-wave sequences also began in the supragranular cells followed by infragranular neurons. 3. We propose that the fast components reflect sequential intralaminar depolarization processes, and the slow waves, hyper- or repolarization processes. These results suggest that a basic neuronal circuit, consisting of sequential activation of the supragranular and then the infragranular pyramidal cells, gives rise to the field potentials evoked by physiological stimulation. This is consistent with our previous studies of direct cortical responses (DCR) and pathological discharges of the penicillin focus.

Animals↗

PubMed1990

Focal functional anatomy of dorsolateral frontocentral seizures.

We compared 6 patients with dorsolateral frontocentral seizures to 7 patients with temporal lobe seizures. We determined general seizure location by structural lesions in 7 patients, bilateral depth electrodes in 4, and EEG and semiology in 2. We then mapped seizure cortex and essential cortex using chronic ECoG arrays. Two ECoG patterns were similar in frontal and temporal seizures. Focal patterns were near lesions and resections. Regional patterns were distant from lesions but not associated with worse surgical outcome. "Dipolar" seizure patterns occurred in one-half of frontal patients with maps like somatosensory evoked responses, consistent with focal seizure anatomy and involvement of sensorimotor cortex. Dipole location estimates were near centers of seizure cortex determined by lesions, semiology, and outcome. Six temporal patients had focal excisions that gave significant seizure reduction in all. All frontocentral patients had focal excisions that significantly reduced seizures except in 1 patient with progressive disease. We conclude that dorsolateral frontocentral seizures have focal functional anatomy that can be predicted by ictal ECoG.

Adult↗

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↗