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Biomedical subjects

G H Wieneke

Publications and source records attributed to G H Wieneke.

At least 37 records · Page 2Linked to original sources
PubMed1999

Decreased transcranial Doppler carbon dioxide reactivity is associated with disordered cerebral metabolism in patients with internal carotid artery stenosis.

PURPOSE: The hemodynamic effect of stenosis of the internal carotid artery (ICA) can be assessed by measuring, with transcranial Doppler (TCD), the carbon dioxide (CO(2)) reactivity of the cerebral vessels. The aim of this study was to determine whether a decreased CO(2) reactivity is associated with a compromised cerebral metabolism, as evaluated with (1)H magnetic resonance spectroscopy (MRS). METHODS: Sixty-six patients with unilateral or bilateral stenosis of the ICA, who were scheduled for carotid endarterectomy (CEA) and who had undergone both a TCD CO(2) reactivity test and a MRS examination, were included in this study. The ICA stenosis on one side (CEA side) was always more than 70%, and the extent of the stenosis on the contralateral side varied. RESULTS: The CO(2) reactivity and the N-acetyl aspartate (NAA)/choline ratio were correlated in both hemispheres (r =.43; P <.001). Patients with an ICA occlusion contralateral to the CEA side are especially at risk for disordered cerebral hemodynamics and metabolism; in the contralateral hemisphere, the mean CO(2) reactivity and NAA/choline ratio were abnormal (18% and 1.52, respectively), and lactate was present in 85% of the patients. Changes indicative of disordered hemodynamics were found more often in symptomatic than in asymptomatic patients. CONCLUSION: A decreased CO(2) reactivity appears to be associated with a disordered cerebral metabolism. Patients with severe bilateral ICA stenosis are at risk for disordered cerebral metabolism and hemodynamics. Therefore, the indication for CEA based on the degree of ICA stenosis and clinical grounds might be refined with an additional test, such as the TCD CO(2) reactivity test.

Aged↗
PubMed1999

Carotid endarterectomy monitoring: patterns of spectral EEG changes due to carotid artery clamping.

OBJECTIVE: The purpose of the study was to make an objective and quantitative analysis of the EEG changes caused by carotid artery clamping during carotid endarterectomy (CEA) monitoring. METHODS: Factor analysis was used to study the intraoperative spectral EEG changes in 94 patients during clamping of the carotid artery. In addition, the relation between the extracted factors and the changes in blood pressure and blood flow velocity in the middle cerebral artery during clamping was studied. RESULTS: Two factors were extracted with factor analysis. The first factor represented a change in power in the alpha and beta frequency ranges in combination with a less pronounced opposite change in power in the delta frequency range. The second factor represented a change in power restricted to the delta and theta frequencies. With the first factor, two types of spectral EEG changes could be distinguished: changes indicative of cerebral ischemia (decrease in fast activity and increase in slow activity) and the opposite changes suggesting cerebral activation (arousal). With the two factors combined, the changes indicative of minor ischemia (decrease in fast activity only) could also be distinguished. CONCLUSION: Further study is required to test whether patients showing the EEG changes indicative of activation or minor ischemia actually require shunting.

Aged↗
PubMed1999

The influence of temperature on nerve conduction in patients with chronic axonal polyneuropathy.

OBJECTIVES: To determine whether the increase in conduction velocity with temperature (deltav/deltaT) is decreased in axonal polyneuropathy and to compare methods to account for low limb temperature in electroneurography. METHODS: Median nerve motor and sensory conduction and tibial nerve motor conduction were measured in 19 patients with chronic idiopathic axonal polyneuropathy at baseline temperature, after warming at 37 degrees C, and after cooling at 25 degrees C. Deltav/deltaT was determined, using the skin temperature difference and the presumed nerve temperature difference of 12 degrees C. The baseline conduction velocity was corrected for 37 degrees C, using mean deltav/deltaT values for normal subjects taken from the literature. RESULTS: Deltav/deltaT was positively correlated with the conduction velocity after warming at 37 degrees C: the lower the conduction velocity, the lower the deltav/deltaT. In nerves with a slow conduction velocity, deltav/deltaT was often zero. As slower conducting nerve fibers have smaller deltav/deltaT values, the decreased deltav/deltaT values in our study are probably related to loss of fast conducting fibers. The corrected conduction velocity was usually faster and considerably less often abnormal than the conduction velocity after warming at 37 degrees C. The latter can be considered the gold standard. CONCLUSION: Deltav/deltaT may be reduced in axonal polyneuropathy. The correction method is, therefore, not suitable to account for low limb temperature, as the conduction velocity is overestimated.

Aged↗
PubMed1999

The intrajudge reliability of the perceptual rating of cleft palate speech before and after pharyngeal flap surgery: the effect of judges and speech samples.

OBJECTIVE: In this pilot study, the reliabilities of the perceptual ratings of four types of speech samples by six judges, with and without expertise in evaluating cleft palate speech, were studied. DESIGN: Pre- and postoperative tape recordings of 15 patients with cleft lip and palate who had undergone a superiorly based pharyngeal flap operation were selected. Five speech-language pathologists and one oral and maxillofacial surgeon perceptually rated the following variables on separate 100-mm visual analog scales: hypernasality, audible nasal emission, intelligibility, misarticulations associated with velopharyngeal insufficiency, voice quality, and the presence or absence of hyponasality. These six variables were rated in four types of speech samples: reading of three sentences, repeating after the speech pathologist of three sentences, 10 sentences containing the aforementioned material, and the same 10 sentences in paired comparison. All speech samples were rerated after 3 months by the same judges. RESULTS: Judges differed largely in the range they used in their rating. Intrajudge reliability of .56 to .78 was found for ratings of hypernasality. No significant differences in intrajudge reliability were found for the ratings with the different types of speech samples. The intrajudge reliability of a judge with expertise was not necessarily higher than of a judge without this expertise. CONCLUSIONS: The improvement in speech is most reliably assessed with speech samples in paired comparison. A speech-language pathologist with expertise in evaluating cleft palate speech does not guarantee a high intrajudge reliability of the rating.

Adolescent↗
PubMed1999

Temporary muscle weakness in the early phase of distraction during femoral lengthening. Clinical and electromyographical observations.

Limb lengthening by distraction osteogenesis has a high complication rate. Much of the response of muscle and nerve to distraction is still unknown. Thirteen children, mean age 12.6 yr (8.4-17.3) were surgically treated by the Ilizarov procedure for acquired and congenital femoral limb-length discrepancy. All children showed a decrease in muscle strength in the quadriceps, shortly after the operation, followed by an improvement before distraction started. After an elongation in the early phase of distraction (1 to 2 cm), muscle weakness was again observed and the muscle strength gradually increased after ending of distraction. To provide an explanation for this clinical observation, in one patient (limb lengthening of 4.1 cm) muscle strength measurements were extended with investigations of Hoffman (H) reflex of m. vastus medialis and determination of muscle-fiber conduction velocity of m. vastus lateralis by using the invasive method (IMFCV). The examinations were performed every two weeks during 20 weeks and 12 weeks after removing the cast. A severe decrease in muscle strength of the corrected limb was found after 1.2 cm of distraction with a recovery in muscle strength before lengthening was ended. EMG study showed the same tendency. Denervation was observed as evidence by positive sharp waves and reduced IMFCV findings. Evidence for reinnervation before lengthening was ended, was found by an increased range of velocities consisting of a combination of slow potentials and gradual increase of the velocity of reinnervated fibers (increased Fast/Slow ratio). The latencies of M waves and H-M interval from both legs separated as well after 2.25 cm of distraction. At the end of the follow-up period, the H-M interval reached the preoperative value. It is suggested that these neurogenic changes are an effect of axonal dysfunction and the local effect due to intraoperative trauma and stretching might affect nerve blood flow adversely.

Adolescent↗
PubMed1999

Autonomic function in patients with hereditary motor and sensory neuropathy type I and Lambert-Eaton myasthenic syndrome.

Noninvasive tests of four autonomic organ systems (vasomotor control, baroreceptor reflexes, sudomotor function and pupillary reflexes) were performed on nine patients with hereditary motor and sensory neuropathy (HMSN) type I and three patients with Lambert-Eaton myasthenic syndrome (LEMS). The results were compared with those of 33 control subjects. Autonomic dysfunction was considered present when at least two of the four organ system tests were abnormal. The three patients with LEMS had abnormal results in two or more different systems, whereas only one of the nine patients with HMSN type I had two abnormal test results. This study demonstrates that autonomic dysfunction is not a common finding in patients with HMSN type I and its presence should alert us to find the cause of this autonomic disorder.

Adolescent↗
PubMed1998

Stomach distension increases efferent muscle sympathetic nerve activity and blood pressure in healthy humans.

Although the enteric nervous system is usually described as a separate and independent entity, animal studies show that gastric distension causes a reflex increase in arterial pressure and a sympathetically mediated increase in heart rate and peripheral vascular resistance. To assess the influence of gastric distension on sympathetic outflow and blood pressure, we recorded muscle sympathetic nerve activity (MSNA) from the peroneal nerve by microneurography in eight healthy volunteers. The stomach was distended by means of a barostat, using a single staircase protocol by which pressure was increased by 2 mmHg every 3 min. Gastric sensory function was assessed at each distension step by using a visual analog scale (VAS) for sensations of fullness, nausea and pain. For comparison, we also performed a cold pressor test. The MSNA increased on barostat-induced gastric distension with an almost concomitant elevation of blood pressure. The increase in both was proportional to the intragastric pressure and both decreased towards initial values after the end of distension. Heart rate increased inconsistently and only at higher distension pressures that were associated with high VAS scores. The opposite was found for the cold pressor test. The results of this study confirm the existence of a functional relationship between gastrointestinal distension and cardiovascular function. Decrease in this gastrovascular response may play a role in postprandial hypotension in the elderly, since the MSNA responses to simulated microgravity decrease with age.

Adult↗
PubMed1997

Cold stress provokes sympathoinhibitory presyncope in healthy subjects and hemodialysis patients with low cardiac output.

BACKGROUND: Sudden hypotension in progressive hypovolemia or during hemodialysis is attributed to sudden inhibition of sympathetic activity. Critical ventricular underfilling seems responsible for this paradox, but it is unknown why the transition from sympathoactivation accompanying hypovolemia to sympathoinhibition is so abrupt. We studied whether brief fluctuation of sympathetic activity induced by cold pressor test (CPT) evokes sympathoinhibition if applied during low cardiac output. METHODS AND RESULTS: Fourteen healthy subjects underwent CPT, lower-body negative pressure (LBNP; -45 mm Hg for 60 minutes), or the combination thereof. CPT alone caused vasoconstriction and increased muscle sympathetic nerve activity, followed by uneventful relaxation. When applied during reduced cardiac output, tachycardia, and vasoconstriction induced by prior LBNP for 6 minutes, CPT again caused vasoconstriction, now followed by acute hypotension in 10 subjects, and was associated with vasorelaxation, relative bradycardia, and fall in muscle sympathetic nerve activity. Eight subjects also experienced acute LBNP-induced hypotension in the absence of CPT, but not until 17 +/- 6 minutes of LBNP. We also performed CPT before and in the final phase of hemodialysis in 8 patients. Before dialysis, the patients tolerated CPT uneventfully, but during hemodialysis, CPT provoked acute hypotension in 5 cases, showing similar withdrawal of vasoconstriction. CONCLUSIONS: This is the first study showing that brief cold stress, tolerated well in normal circulatory conditions, can provoke sudden sympathoinhibition and hypotension when applied during decreased cardiac output induced by LBNP or hemodialysis. We suggest that during conditions of a decreased cardiac output, subtle sympathetic relaxation such as follows cold stress triggers self-enhancing relaxation that cannot be controlled.

Adult↗
PubMed1997

The effect of relative humidity of inhaled air on acoustic parameters of voice in normal subjects.

The hypothesis that relative humidity (RH) of air exerts an effect on voice has been widely accepted. The aim of this study has been to assess whether this can be demonstrated. Eight healthy subjects inhaled during ten minutes three different air conditions: dry, standard room, and humidified air. After inhalation, the subjects produced repeatedly a sustained /a/ of controlled pitch and loudness, which was analyzed for perturbation and noise-to-harmonic parameters. Perturbation measures increased after inhalation of dry air. No significant differences existed between standard and humidified air. No significant difference in the noise-to-harmonic ratio was found among the three conditions. We conclude that the human voice is very sensitive to decreases in RH of inhaled air, because even after a short provocation with dry air, a significant increase in perturbation measures was found.

Adult↗
PubMed1997

Clinical relevance of the fractal dimension of F0 perturbations computed by the box-counting method.

The box-counting method for determining the fractal dimension (Dfj) was applied to the fundamental frequency (F0) perturbations in normal and pathological voices in order to assess its clinical value. The upper limit of these Dfj values was similar for both groups, but the distribution for pathological voices extended to lower values than for the normal voices. However, these lower values were most probably the result of one or a few outlying frequency points due to incorrect determination of the vocal period. The Dfj of normal voices were within the range of values found for randomly varying F0 values. It was concluded, that the vocal perturbations in pathological voices are also more or less randomly distributed. So, the Dfj, at that least determined with the box-counting method, do not contain clinically relevant information in addition to the traditional measures for the extent of the vocal period perturbations. An exception is special perturbation types like diplophonia. The result of the computation is very sensitive for voice breaks and vibrato and depends on the number of periods.

Electronic Data Processing↗
PubMed1997

Dipole source analysis may differentiate benign focal epilepsy of childhood with occipital paroxysms from symptomatic occipital lobe epilepsy.

The aim of the study was to distinguish Benign Focal Epilepsy of Childhood with Occipital Paroxysms (BEOP) from its symptomatic counterpart on the basis of the location of the sources of the interictal EEG spikes. Patients were classified into two groups: idiopathic BEOP and symptomatic occipital lobe epilepsy. Source analysis of the averaged occipital spikes was performed using a homogeneously conducting sphere as the volume conductor model. Results showed a statistically significant difference in the eccentricity, i.e., the distance of the occipital spike focus from the centre of the head. The dipole sources of the occipital spikes in the BEOP group were found to be located more superficially than in the symptomatic group, corresponding in six of the nine cases with a source position estimated to be within the cortical layer just below the skull. The eccentricity of the symptomatic occipital spikes suggests a location deeper than the cortical layer. The results were validated in two patients from the symptomatic group. In one patient the estimated deeper dipole source location corresponded with a deeper location of spike activity observed during ECoG; in the other patient's ECoG, spike activity was observed superficially but over an extended area. The discrepancy between estimated and real location may be explained by the method of dipole source analysis used. It is concluded that the finding of a superficial dipole source location of the occipital spikes provides an indication for the diagnosis BEOP (sensitivity: 67%; specificity: 74%).

Adolescent↗
PubMed1997

Seizure semiology of occipital lobe epilepsy in children.

PURPOSE: Occipital lobe epilepsy in children occurs as an idiopathic form, i.e., Benign Epilepsy with Occipital Paroxysms (BEOP), and a symptomatic form. This study attempted to determine whether seizure semiology could distinguish between the two forms. METHODS: Fifty children (34 boys, 16 girls) with clinical seizures and interictal EEGs presenting occipital spikes were included consecutively in the study. Seizure onset was between the ages of 2 months and 15 years. Epilepsy was considered symptomatic when psychomotor retardation and/or abnormalities at neurological and/or neuroradiological examination were found: 17 children were classified as idiopathic, and the remaining 33 children were classified as symptomatic. Seizure semiology was assessed by means of a structured interview of the children and their parents, using a detailed questionnaire. Seizure semiology was determined to comprise motor (versive or other movements of the eyes, versive movements of the head, (hemiconvulsions), visual, other signs (e.g. vomiting and headache), and impairment of consciousness. RESULTS: There were no statistically significant differences in seizure semiology between the two groups. CONCLUSIONS: Seizure semiology cannot distinguish between different forms of occipital lobe epilepsy: Further clinical examination, clinical neurophysiological investigations, and neuroimaging studies are needed for a correct classification.

Adolescent↗
PubMed1997

Bilateral increase in CO2 reactivity after unilateral carotid endarterectomy.

BACKGROUND AND PURPOSE: A low or absent CO2 reactivity is considered indicative of a compromised hemodynamic compensatory capacity in patients with internal carotid artery (ICA) stenosis or occlusion. The aim of the present study was to investigate whether patients with preoperatively decreased or absent CO2 reactivity show an improvement of CO2 reactivity 3 months after carotid endarterectomy (CEA) and whether the preoperative CO2 reactivity is correlated with clinical classification and hemodynamic factors. METHODS: A group of 65 patients with > 70% ICA stenosis was studied. CO2 reactivity was measured by bilateral transcranial Doppler sonography before and 3 months after CEA. RESULTS: The preoperative CO2 reactivity was not significantly different in subgroups formed according to the presenting clinical symptoms. Patients with severe ICA stenosis with contralateral ICA occlusion had mean low preoperative CO2 reactivity on both sides. Furthermore, patients with reversed flow in the ophthalmic artery had low mean preoperative CO2 reactivity on the same side. The CO2 reactivity was not significantly different in the subgroups of patients with signs of collateral blood flow through the anterior or posterior communicating artery. In particular, patients with low preoperative CO2 reactivity (approximately < 30%) showed an evident increase after the operation. Such an inverse correlation was found bilaterally, although it was more pronounced on the CEA side. CONCLUSIONS: CEA can increase CO2 reactivity in both hemispheres. This effect is most pronounced in patients with low (< 30%) preoperative CO2 reactivity. If this group represents patients who would be at risk from low-flow stroke, then testing of CO2 reactivity might help select a subset of patients with an especially high probability of benefit from CEA.

Aged↗
PubMed1996

Source modeling of esophageal evoked potentials.

Evoked potentials can be recorded from the scalp after stimulation of the esophagus by balloon distension. The purpose of this study was to estimate the number and localization of sources contributing to the esophageal evoked potential (EEP). The EEP was recorded from 32 scalp electrodes in 5 healthy subjects. Spatio-temporal dipole modeling was performed in the time interval from 185 msec to 525 msec after stimulation (mean values). The EEP was best explained by the combined activity of 1 dipole located relatively high in the midline and 2 lateral dipoles. Given the anatomical projection of esophageal sensory fibers and the location of these dipoles the sources were probably located in the cingulate gyri and insular cortex. There was no evidence that sources in the lower brain-stem contributed to the scalp recorded EEP.

Adult↗
PubMed1996

The impact of repeated short episodes of circulatory arrest on cerebral function. Reassuring electroencephalographic (EEG) findings during defibrillation threshold testing at defibrillator implantation.

The impact of circulatory arrest on EEG features during defibrillation threshold testing for implantation of a cardioverter defibrillator has been disputed. Cumulation of cerebral ischemic effects during threshold testing has been observed, and consequently the advice was given to avoid short intervals between tests and to limit the test number. This study investigated the duration of EEG signs of cerebral ischemia as well as the occurrence of cumulation. EEGs were recorded during standardized general anesthesia. Subsequent tests were performed after recovery of EEG, electrocardiogram, systemic arterial blood pressure, and heart rate. In 36 consecutive survivors of out-of-hospital cardiac arrest 286 episodes of induced circulatory arrest were analyzed. Ischemic EEG changes were present in all episodes of circulatory arrest, consisting of slowing, progressing to absence of activity. The relation between the onset time or recovery time and the test number and test interval was studied. A highly significant correlation between circulatory arrest and recovery time was found (P < 0.001). A significant negative correlation existed between test number and recovery time (P < 0.05). Test interval was not related with either onset or recovery time. We conclude that repeated threshold tests which are monitored by assessment of EEG and hemodynamics are not associated with cumulative EEG changes as a result of ischemia. Our results do not support the advice that the number of tests should be limited.

Adolescent↗
PubMed1996

Fo-perturbation and Fo/loudness dynamics in voices of normal children, with and without education in singing.

Sustained phonations were compared in two groups of children (aged 7-12), one with special artistic voice education and one from a normal school, without voice complaints or problems. The hypothesis of specific (better) biomechanical vocal fold properties in the first group is confronted with the hypothesis of differences solely related to training of voice control. In both groups, Fo-aperiodicity was measured in a sustained phonation at 3 different SPL levels. As a general rule, aperiodicity clearly decreases when the voice becomes louder. Aperiodicity is highly significantly lower, at all SPL-levels, in children with trained singing voices: this implies better mechanical properties of the vocal oscillator. The Fo/SPL relation on a sustained /a:/ does not differ in trained and untrained children's voices: out of singing context, trained children do not spontaneously control the Fo/SPL dynamics differently from untrained children. The higher regularity of vocal fold pulses is not related to the duration of training.

Biomechanical Phenomena↗
PubMed1996

The contribution of conventional and quantitative electroencephalography during monitoring of exposure to hyperbaric oxygen.

In the present study, experimental exposures to hyperbaric oxygen (HBO) were performed (30-min exposure to 2.8 bar pure oxygen). During all phases of the experiment the electroencephalogram (EEG) was recorded continuously for on-line visual monitoring and off-line quantitative analysis. Conventional and quantitative EEG findings are described for a group of 23 subjects during an uncomplicated HBO exposure and for one subject who had a generalized tonic-clinic seizure when exposed to HBO. In the group of subjects who did not show signs of toxicity, EEG changes were minor and were not considered indicative of an adverse effect of HBO on the brain during the HBO exposure. Pre-convulsive EEG changes were detected in the subject with the seizure but were too insignificant for practical monitoring purposes and did not clearly herald clinical signs.

Adult↗