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Biomedical subjects

M Hennerici

Publications and source records attributed to M Hennerici.

At least 163 records · Page 9Linked to original sources
PubMed1990

[Spectrum analysis of Doppler signals].

Doppler signal spectrum analysis contains useful haemodynamic information. Several parameters of the spectrum can be documented in numerics. Random interaction of the reflectors, the size of the ultrasound sample volume and the procedure of signal analysis influence the results and hence may cause misinterpretation of the data selected. Essential mechanisms influencing the clinician's Doppler-spectrum-analysis are discussed on the basis of a series of 59 angiographically and sonographically examined carotid arteries as well as in the light of theoretical considerations and a review of the literature. Peak frequency linked with a battery of spectrum parameters accuracy are useful to differentiate various degrees of lumen narrowing. Identification or exclusion of minor plaques cannot be achieved with sufficient sensitivity and specificity.

Carotid Arteries↗
PubMed1990

Compensatory mechanisms in patients with asymptomatic carotid artery occlusion.

Twelve patients with asymptomatic occlusion of one (n = 8) or both (n = 4) internal carotid arteries were examined by positron emission tomography (PET) and transcranial Doppler ultrasound. PET measurements included the determination of the regional cerebral blood flow (rCBF), oxygen extraction ratio (rOER), cerebral metabolic rate of oxygen (rCMRO2), and cerebral metabolic rate of glucose consumption (rCMRGlc). Transcranial Doppler ultrasound (TCD) was used to determine the pathways and efficacy of collateralization via the circle of Willis and included spectrum analysis of flow velocities within the middle and anterior cerebral arteries as well as vasoreactivity tests. In correspondence with ultrasound evidence of a haemodynamically effective intracranial collateral circulation no significant differences between patients and controls were observed for rOER, rCMRO2 and rCMRGlc, but rCBF was globally reduced. Furthermore, in all patients with unilateral carotid occlusion PET excluded side asymmetries of any parameter studied. In contrast, flow velocity parameters measured by TCD were significantly reduced ipsilateral and significantly increased contralateral to the carotid obstruction. Vasodilative capacities, however, remained preserved even in the territory of the occluded carotid system. These data indicate that patients with asymptomatic carotid occlusion compensate by haemodynamic and not by metabolic mechanisms in contrast to symptomatic patients.

Aged↗
PubMed1990

Cerebral blood flow velocity alterations during obstructive sleep apnea syndrome.

We recorded cerebral blood flow velocity (CBFV) for the assessment of CO2-regulated alterations during apnea by means of transcranial Doppler ultrasound in a patient with obstructive sleep apnea syndrome. CBFV increased up to doubled peak flow values during obstructive apneic phases. The results provide evidence for a normal CO2 regulation of CBFV leading to periodic vascular stress during the night.

Blood Flow Velocity↗
PubMed1990

Carotid artery disease assessed by color Doppler flow imaging: correlation with standard Doppler sonography and angiography.

Carotid artery disease was assessed in 180 patients by means of color Doppler flow imaging. Color Doppler findings in 360 carotid arteries were compared with the results of standard Doppler sonography, and color Doppler findings in 60 bifurcations were compared with the results of intraarterial angiography. The sensitivity of color Doppler for the detection of carotid disease was 100% when compared with angiography. The accuracy of color Doppler in classifying minor (40-60%), moderate (61-80%), and severe (81-90%) stenosis ranged from 91.3% to 97.8% vs standard Doppler sonography, and from 91.7% to 95.8% vs angiography. Whereas all occlusions were identified correctly by both color Doppler and angiography, four pseudoocclusions of the carotid artery were misdiagnosed as occluded. Characteristic features providing reliable criteria of the degree of stenosis are (1) intensity, extent, and duration of color fading; (2) postprocessed systolic peak frequency; (3) plaque extent on serial sonograms; and (4) poststenotic flow patterns. Display of hemodynamic disturbances induced by less pronounced plaques showed highly variable patterns that could not be anticipated from the plaque morphology alone. Thus, color Doppler preserves the advantages of standard Doppler and duplex sonography but provides additional information about otherwise anechoic necrotic and thrombotic material that often causes cerebral embolisms. With atherogenesis, repair mechanisms may be sustained or progression be stopped by reducing the risk factors and instituting medical treatment; thus, the application of this noninvasive technique is important.

Adult↗
PubMed1990

Effect of nimodipine on acute ischemic stroke. Pooled results from five randomized trials.

In a review of pooled data from five double-blind, placebo-controlled studies of nimodipine in acute ischemic stroke, we compared the effect of 120 mg nimodipine given orally with that of placebo. In the five studies, 871 patients were followed, and 781 adhered to entry and inclusion criteria. End points were mortality and outcome at the end of the treatment period (21 or 28 days). Outcome was assessed with Mathew's scale and the physician's clinical judgement. The treatment and control groups were well matched with respect to demographic data, risk factors, and baseline Mathew scores. In the treatment group, 34 patients (7.9%) died during the treatment period, whereas 54 (12.3%) in the control group died, corresponding with a mortality reduction of 36%. Significantly less neurologic impairment at the end of the treatment period was documented under nimodipine treatment, and this impairment improved more in patients with moderate-to-severe stroke (baseline Mathew score less than 66) if administration of nimodipine occurred within 12 hours after stroke onset or if the patient was more than 65 years old. The overall incidence of adverse reactions was relatively modest, and these were of minor severity; only a few appeared to have more than a remote relation to the study medication.

Aged↗
PubMed1989

[Diagnosis and progress of carotid artery dissecting aneurysm].

33 patients with angiographically confirmed dissection of the internal carotid artery (ICA) were followed prospectively. Cardinal symptoms were: 1) focal disturbances of the cerebral circulation (n = 28); 2) unilateral headache or neck pain (n = 20); 3) incomplete Horner's syndrome (n = 9). Neurological deficits without pain or sympathetic nerve damage developed in 11 patients. All patients had abnormal Doppler ultrasound findings over the ICA; in 22 there were markedly reduced flow velocities and retrograde flow components ("to- and- fro" phenomenon), typical of carotid artery dissection. During a mean observation time of 6.9 +/- 5.7 months serial Doppler ultrasound and angiographic examinations demonstrated recanalization in 73% after an average of 56 days. Angiographically different types (long segments in 13; pseudo-occlusions in 7; pseudoaneurysms in 5; and distal stenoses in 6; others in 2) are interpreted as expressions of different stages in the development of dissection up to complete recanalization.

Adolescent↗
PubMed1989

High-resistance Doppler flow pattern in extracranial carotid dissection.

Internal carotid artery dissection is an increasingly recognized cause of cerebrovascular events. The diagnosis is conventionally established on the basis of characteristic clinical symptoms and arteriographic findings. However, the presence of characteristic hemodynamic features detected by ultrasound may already suggest the diagnosis, even in atypical cases. This is demonstrated in 16 (76%) of 22 patients with internal carotid artery dissection. An intense systolic low-frequency Doppler signal of alternating flow direction accessible in the neck, either along the extent of a luminal tapering stenosis or proximal to a severe obstruction at the skullbase, indicated this diagnosis. Resolution or decreasing stenosis may similarly be diagnosed noninvasively, as shown by results from subsequent arteriograms in 14 patients (64%). This occurred suddenly during sequential follow-up between 2 days and 30 weeks (mean, 6 weeks) after the diagnosis was made.

Adolescent↗
PubMed1989

[Duplex sonography of the internal jugular vein].

Based on defined diagnostic criteria high-resolution Duplex sonography allows the accurate evaluation of normal and pathological jugular vein. Compared to examinations with only the B-mode the diagnostic accuracy is higher with the duplex system with additional display of venous flow signals. Normal findings and results of duplex sonography in patients with venous inflow congestion, thrombosis and aneurysm of the jugular vein are presented, and their clinical relevance of the method discussed.

Aneurysm↗
PubMed1989

Long-term follow-up of carotid disease: clinical and ultrasound aspects.

Various non-invasive techniques were used to study clinical and ultrasound aspects of extracranial arterial disease. cw Doppler was used prospectively to study the natural history of asymptomatic extracranial arterial disease (greater than 50% carotid stenosis, subclavian steal phenomena) in 401 patients. Whereas the cumulative death rate was high (44%) at 8 years, the stroke rate was low (6%). Progression of the vascular processes during follow-up correlated with later cerebrovascular events. Transcranial PW Doppler was used to study the intracranial collaterlisation in 151 asymptomatic patients with significant extracranial lesions. The majority of patients showed excellent collateralisation. The natural history of non-stenotic plaques (less than 30% carotid stenosis) was studied by means of high-resolution (10 MHz) duplex system analysis. Whilst most plaques remained constant during the subsequent follow-up period progression was seen in 24% and regression in 10%.

Carotid Artery Diseases↗
PubMed1989

Flow pattern and structural changes at carotid bifurcation in hypertensive cynomolgus monkeys.

Blood flow pattern and morphological changes within the extracranial carotid system were studied in M. fascicularis before, immediately after, and at various intervals (4 hours, 4 days, 10 days, and 4 weeks) after the introduction of systemic hypertension by surgical coarctation of the thoracic aorta. Intra-arterial hemodynamics were assessed by means of both continuous-wave Doppler signal spectrum analysis and multigate pulsed-wave Doppler flow velocity profile processing. Diminished peak frequencies throughout the carotid system and enlargement of the lumen diameter in the common carotid artery and the carotid bulb were major findings and were suspected to be due to cerebral autoregulation at high levels of intracranial vascular resistance. In the internal carotid artery of pure muscular type, the lumen diameter was diminished so the carotid bulb became an area of structural and hemodynamic transition. As a consequence, flow irregularities already observed in this region before surgery considerably increased during hypertension. In addition, endothelial disarray and leucocytic adherence and activation were associated with these hemodynamic alterations within the carotid bulb. Their mutual role in early atherogenesis is discussed.

Animals↗
PubMed1989

Doppler color flow imaging of carotid body tumors.

Doppler color flow imaging is a new ultrasound method for the simultaneous spatial display of tissue and vessel morphology (B-mode echotomograms) and of color-coded blood flow velocity information (Doppler-mode analysis). This new method is particularly useful in the neck, not only for the assessment of brain arteries but also for the safe and valid identification of carotid paragangliomas compared with other neck tumors. Early clinical detection of carotid paragangliomas is difficult since these lesions often occur sporadically and the patients remain symptom-free until the tumor becomes noticeable. Doppler color flow imaging allows the diagnosis of even small paragangliomas, which may improve management because of existing complications of surgical therapy.

Adult↗
PubMed1988

Familial multiple sclerosis.

Siblings of patients with multiple sclerosis have an increased risk of developing the disease. In this report we describe 3 families with multiple affected members, representing the largest published aggregation of cases in first degree relatives. In the 2 families in which HLA tissue-typing was performed the affected individuals shared part of the haplotype HLA-DR2 (+ HLA-DQW1), BfS (+ C2C), C4A3, C4B1. The implications of these findings for the aetiology of multiple sclerosis are discussed.

Adolescent↗