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Biomedical subjects

M Hennerici

Publications and source records attributed to M Hennerici.

At least 145 records · Page 8Linked to original sources
PubMed1992

Imaging in cerebrovascular disease.

High-resolution structural imaging of ischemic lesions now enables the assignment of complex ischemic clinical symptoms to cortical and subcortical lesions. Functional imaging shows some new features of cerebral ischemia which can be directly investigated in the individual patient. Vascular imaging is rapidly improving with the introduction of magnetic resonance angiography (MRA). Today its diagnostic value is unsettled but promising, in particular if used in combination with other techniques like ultrasonography and positron emission tomography (PET).

Brain Ischemia↗
PubMed1991

Spontaneous oscillations in cerebral blood flow velocity in normal humans and in patients with carotid artery disease.

Spontaneous oscillations in cerebral blood flow velocity (CBFV) in normals and in patients with stenoses or occlusions of the internal cerebral artery were measured using transcranial Doppler sonography. In normal subjects, large oscillations of up to +/- 30% from the mean CBFV were found with low frequencies between 0.4 and 9 cycles/min. No correlations between CBFV oscillations and systemic circulatory parameters were detected. In patients with carotid artery obstructions the CBFV oscillations were significantly reduced in the middle cerebral artery ipsilaterally to a hemodynamically significant lesion, but not contralaterally. Our results support the hypothesis that spontaneous oscillations (B-waves) of small pial vessels are responsible for the CBFV fluctuations.

Adult↗
PubMed1991

Orthostatic changes of cerebral blood flow velocity in patients with autonomic dysfunction.

Simultaneous registrations of intracranial blood flow velocity parameters achieved by transcranial Doppler sonography and basic cardiovascular parameters were carried out during orthostatic changes in normal controls, diabetic patients and patients with pandysautonomia. Normal subjects had a rapid increase in heart rate at a constant blood pressure and a slight decrease in cerebral blood flow velocities associated with a mild increase of the pulsatility index (PI) after being tilted from a horizontal to a vertical position. Diabetics showed a fixed heart rate reflecting the disturbed autonomic innervation but only minor changes of cerebral blood flow velocity, which is similar to normal cerebrovascular autonomic regulation. Patients with pandysautonomia had a fixed heart rate associated with a decrease of systemic blood pressure but a failure of compensatory cerebral autoregulation to maintain normal flow velocity values after standing up. The results suggest that in diabetics cerebrovascular autonomic regulation is intact in contrast to cardiac autonomic function, while in patients with pandysautonomia both functions are disturbed. Criteria for the interpretation of autonomic regulatory mechanisms involved in cerebrovascular flow measurements are discussed.

Adult↗
PubMed1991

Spectral composition of Doppler signals.

The spectral content of the Doppler signal (as revealed by spectral analysis) provides useful diagnostic information about local hemodynamic conditions. Changes in these conditions are used to diagnose atherosclerotic lesions in arteries accessible to ultrasound. Extremely high frequencies, as found in and distal to a tight stenosis, indicate the presence of a jet, while Doppler signals with a wide bandwidth are related to regions with wide velocity ranges and/or disturbed flow patterns. However, the random interactions of the scatterers, the dimensions of the sample volume, the velocity of the scatterers and the method of signal processing used affect the displayed spectral composition of the Doppler signal. This article reviews the basic mechanisms and cautions the investigator against a quick and superficial interpretation of the results obtained without a proper appreciation of the random fluctuations due to the methods used to record and process the signals.

Humans↗
PubMed1991

Doppler colour flow imaging after carotid endarterectomy.

Sixty-six patients (72 carotid arteries) were examined after carotid endarterectomy (CEA) using Doppler colour flow imaging (DCFI). Examinations were performed 4-18 days (mean: 7 days) after surgery (32 patients, 34 arteries) or between 2 and 100 months (mean: 39 months) after CEA (34 patients, 38 arteries). Minor vessel wall abnormalities were found in 36% in the internal carotid artery (ICA) and in 55% in the common carotid artery (CCA) or bifurcation. One patient had a minor residual ICA stenosis after surgery; two low-grade stenoses and three ICA-occlusions were diagnosed at follow-up. Altered flow patterns occurred most in CCA (90%) and were predominantly located adjacent to the vessel wall and in dilated vascular segments of the CCA. Disturbed haemodynamics in the ICA were less marked (57%) and frequently found in the central vessel lumen or diffusely distributed. We conclude that surgically induced changes of the vessel geometry and residual or recurrent vascular wall abnormalities are often associated with distinct haemodynamic disturbances, which can reliably be detected by DCFI.

Blood Flow Velocity↗
PubMed1991

Regression of carotid plaques during low density lipoprotein cholesterol elimination.

We performed serial prospective ultrasound examinations of four flat and 17 soft carotid plaques during an average of 17 months in seven patients with heterozygous hypercholesterolemia during heparin-induced extracorporeal low density lipoprotein elimination on precipitation from plasma. By means of a specially designed quantitative three-dimensional ultrasound analysis, significant plaque volume reduction could be evaluated in all subjects, along with a marked reduction of total and low density lipoprotein cholesterol and fibrinogen serum levels.

Adult↗
PubMed1991

[The value of duplex sonography in cerebral ischemia].

Doppler color flow imaging (DCFI) is a new ultrasound technique for the assessment of extracranial arterial disease. This system is a further development of conventional duplex systems. The new technique provides a real-time gray-scale echotomogram (B-mode) and simultaneously superimposed color-coded Doppler signals of intravascular blood flow. The advantages of the DCFI are improved identification of vascular structures, faster data acquisition, shorter examination time, better characterization of the surface, structure and extent of plaques with easier detection of ulcerative lesions or thrombotic material. Due to these advantages, the sensitivity for the detection of lesions which may cause arterio-arterial embolisms to the brain, is increased. With DCFI, it is possible to visualize the extracranial portion of the vertebral arteries. This improves the evaluation of the vertebro-basilar circulation. DCFI is a safe and fast method in the follow-up procedure of symptomatic and asymptomatic patients and after carotid endarterectomy. Using DCFI, the interaction between morphology and hemodynamics in the extracranial vessels can be analyzed, which is important particularly for the understanding of the potential risk of different plaque types.

Aortic Dissection↗
PubMed1991

[Cerebrovascular disorders--clinical aspects and follow-up].

The observation of the spontaneous course of the extracranial vascular process as a characteristic cause of cerebral ischemia has shown that vascular changes occur largely independently from the appearance of cerebral functional disturbances in the associated vascular territory. Hemodynamic factors play a minor role; while with the present standard methods available, embolic mechanisms can be insufficiently analyzed. The prospective developmental observations of morphologic and fluid-dynamic aspects and supplemental cell biology and metabolic analysis provide new criteria for an individual risk evaluation of the various mechanisms causing pathologically different cerebral function disturbances, and their analysis has crucial significance for a therapy plan.

Adult↗
PubMed1990

Transcranial Doppler ultrasonography versus arteriography for assessment of the vertebrobasilar circulation.

The investigation of the vertebrobasilar arterial system by transcranial Doppler (TCD) ultrasonography is difficult due to the numerous anatomical variations in the posterior circulation. To test the validity of TCD, we compared topographic measurements from vertebrobasilar angiograms and corresponding TCD findings in 58 patients with cerebrovascular diseases (N = 37, 21 affecting the vertebrobasilar system), brain tumors (N = 8), and other neurological diseases (N = 13). Normal TCD recordings of the vertebrobasilar system were confirmed by the angiograms in 25 patients, although the noninvasive method failed to separate morphologic variants (N = 15). In patients with pathological conditions of the vertebrobasilar system revealed by either method (N = 17), the combined use of both hemodynamic and radiomorphologic methods improved the diagnostic validity in 24%. We conclude that TCD examination of the posterior fossa circulation provides unambiguous results only if used in combination with cerebral arteriography.

Adult↗
PubMed1990

Doppler color flow imaging of common carotid artery dissection.

Sonographic findings are reported in a case of common carotid artery dissection assessed by Doppler color flow imaging and confirmed by angiography. Advantages and clinical relevance of this new ultrasound method for this diagnosis are discussed.

Aortic Dissection↗
PubMed1990

Variability of flow patterns in the normal carotid bifurcation.

One hundred and nine carotid bifurcations of 56 healthy subjects were examined by means of a Doppler color flow imaging (DCFI) system. Flow separation was found in 102 (93.6%) bifurcations. Different patterns of the spatial and temporal distribution of flow separation zones could be distinguished: separated flow was either restricted to the proximal external (5.9%), the internal (34.3%) or both carotid arteries (40.2%). In 11.8% zones of secondary flow extended from the internal into the external carotid artery around the flow divider, and in 7.8% the distribution was diffuse. The maximum of reversed flow signals occurred immediately after the systolic peak (73%) but lasted for highly variable intervals throughout the cardiac cycle. This demonstration of the unexpectedly various spatial and temporal patterns of secondary flow phenomena contrasts with concepts from in vitro flow studies. This information about conditions in vivo must be considered in investigations of early atherosclerosis in the human carotid bifurcation.

Adolescent↗
PubMed1990

Prognosis of asymptomatic carotid occlusion.

Ninety-four asymptomatic patients with internal carotid artery occlusion were followed for a mean of 44 months, 16% suffered strokes and 11.7% reported transient ischemic attacks (TIA). The annual stroke and TIA rates were 4.4% and 3.2%, respectively, the annual mortality was 11.3%. In 27 asymptomatic patients progression of extracranial arterial disease to occlusion was observed: 7.4% of these patients suffered from stroke and 18.5% reported TIA's during that period. Thus the annual stroke rate was lower (1.9%) but the TIA rate higher (4.7%) than post-occlusive rates. These data reflect an increase risk in patients with progressive high-degree carotid stenosis which continues after occlusion. This may favour carotid endarterectomy for selected patients in the pre-occlusive state because medical treatment has not been shown to prevent progression of stenosis to occlusion.

Arterial Occlusive Diseases↗
PubMed1990

New technical and clinical aspects for cerebrovascular applications of ultrasound methods.

Various Doppler-ultrasound methods have been established for the evaluation of both extracranial and intracranial vascular diseases. The validity of the presently used techniques and new aspects of work in progress are demonstrated and discussed in detail because of the increasing clinical interest in detailed vascular information for prospective follow-up investigation.

Cerebrovascular Circulation↗