PubMed Health⌕ Search

Biomedical subjects

R W Baumgartner

Publications and source records attributed to R W Baumgartner.

At least 73 records · Page 4Linked to original sources
PubMed1996

Transcranial colour-coded duplex sonography of cerebral arteriovenous malformations.

A transcranial colour-coded duplex sonography (TCCD) study was performed to evaluate the sensitivity of detection and the feasibility of visualising details of cerebral arteriovenous malformations (AVMs). We prospectively examined 15 patients with 2 large (> 4 cm), 7 medium-size (2-4 cm) and 6 small (< 2 cm) radiologically proven supratentorial AVMs of the brain using TCCD. A feeding vessel was diagnosed if the velocities and/or the relative interhemisphere velocity difference between feeding and non-feeding anterior, middle and posterior cerebral arteries were more than two standard deviations above the means of 136 age- and sex-matched normals. The sonographer was blinded to the results of cerebral angiography. Using TCCD it was possible to detect all large and medium-size lesions, and 4 of 6 small ones, because 23 of 29 (79%) feeding arteries showed abnormal haemodynamics. In addition, 8 of 46 (17%) feeding branches of cerebral arteries were shown. However, all but 2 large draining veins and sinus were not detected. In view of the availability of MRI, MRA and angiography, TCCD is not the method of choice in screening for cerebral AVMs. However, careful assessment of the velocities in the intracranial arteries permits incidental detection of cerebral AVMs and characterisation of the haemodynamics in the feeding arteries.

Adult↗
PubMed1996

Ultrasonic-pathologic comparison of postangioplasty myointimal hyperplasia and primary atheroma of the superficial femoral artery.

The purpose of this study was to characterize postangioplasty myointimal hyperplasia as compared to primary atheroma of superficial femoral arteries using color-coded duplex sonography (CCD), and to correlate sonographic findings with the histopathology of samples obtained from these lesions by catheter atherectomy (Redha-cut device). Preinterventionally, homogeneity, echogeneity, and the surface of plaques were described using CCD in nine cases with secondary stenoses after percutaneous transluminal angioplasty and in seven cases with primary atheroma. Myointimal hyperplasia of femoral restenoses showed a homogeneous (7 of 9 vs. 1 of 7) and hypoechogenic (7 of 9 vs. 0 of 7) wall thickening compared to primary atheromas (p < 0.05). Primary atherosclerotic plaques showed a rather heterogeneous, hypo- and hyperechogenic ultrasonic appearance with or without echo shadowing in six of seven cases. The surface of restenoses was more often regular than that of primary atherosclerotic lesions, but this finding did not reach statistical significance (6 of 9 vs. 2 of 7, p = 0.14). Thrombotic material appeared homogeneous and hypoechogenic in three of five cases and could not be discriminated from intimal hyperplasia. In summary, postangioplasty intimal hyperplasia is characterised by a hypoechogenic, homogeneous, rather regularly confined vessel wall thickening and can be differentiated from primary atheroma at CCD.

Aged↗
PubMed1996

[Transcranial Doppler and color duplex ultrasound. Familiar and new uses].

Transcranial Doppler and color-coded duplex sonography provide reliable information on cross-flow through the circle of Willis, stenoses, occlusions and vasospasm of the major basal cerebral arteries. The CO2 and acetazolamide tests allow quantitative evaluation of the hemodynamic impact of obstructive cerebrovascular disease. Furthermore, transcranial Doppler sonography is used for detection of enhanced intracranial pressure, confirmation of brain death, detection of cerebral microemboli ("high intensity transient signals" = "HITS"), and patent foramen ovale. In the future, cerebral microemboli may become a marker for embolic activity of both occlusive carotid artery and cardiac disease. Transcranial color-coded duplex sonography identifies intracranial hemorrhage, cerebrovascular malformations, and hydrocephalus, but is inferior to neuroradiological techniques. Transpulmonary contrast agents make the examination of patients with inadequate insonation windows feasible, and increase diagnostic confidence in transcranial ultrasonography. Transcranial power-based color-coded duplex sonography ("power Doppler") may further improve transcranial ultrasonography, and visualize flow in smaller vessels.

Cerebrovascular Disorders↗
PubMed1996

Comparative study of power-based versus mean frequency-based transcranial color-coded duplex sonography in normal adults.

BACKGROUND AND PURPOSE: Power-based transcranial color-coded duplex sonography (p-TCCD) is a new ultrasonic method that has advantages compared with frequency-based TCCD (f-TCCD), since it is essentially independent of the angle of insonation, not subject to aliasing, and has a better signal-to-noise ratio. The purpose of this study was to evaluate the ability of p-TCCD to visualize flow in cerebral parenchyma and to compare the advantages, limitations, and reliability of velocity measurements of p-TCCD versus f-TCCD in the major basal cerebral arteries of normal subjects. METHODS: Two investigators performed 15 p-TCCD and 15 f-TCCD studies in 30 normal subjects with adequate ultrasonic windows. Each investigator did a p-TCCD or f-TCCD study in every patient, and each was blinded in every case to the results of the other. Peak systolic (Vs) and end-diastolic (Vd) velocities were determined in the anterior, middle, and posterior cerebral, basilar, and vertebral arteries. The reliability of p-TCCD velocimetry was evaluated by calculating both the correlation coefficient (r) of the difference between p-TCCD versus f-TCCD measurements and the coefficient of variation (CV), defined as the difference between the mean values for p-TCCD and f-TCCD divided by the mean values for f-TCCD measurements, expressed as percent. RESULTS: p-TCCD did not display flow in cerebral parenchyma but depicted arteries with a course perpendicular to that of the ultrasound beam and showed good reliability of velocity measurements in all examined arteries: for Vs, r was .84 to .93 (P < .001) and CV was 7.7% to 10.8%; for Vd, r was .87 to .90 (P < .001) and CV was 10.3% to 13.7%. The lack of directional and velocity information and tissue motion artifacts were unimportant limitations in p-TCCD. CONCLUSIONS: Compared with f-TCCD, p-TCCD had no important advantages but had several unimportant limitations in a study of normal adults with adequate ultrasonic windows.

Adult↗
PubMed1996

[Cerebrovascular ultrasound diagnosis].

Introduction of color-coded duplex sonography has further increased diagnostic confidence of neurovascular ultrasound. Thus, reliable and noninvasive preoperative assessment of patients with carotid artery stenoses becomes feasible, preventing potential adverse effects of cerebral angiography. Moreover, reliable diagnosis of subtotal stenoses and occlusions of the carotid arteries is possible. Transcranial ultrasonography provides reliable assessment of cross-flow through the circle of Willis, and stenoses, occlusions and vasospasm of the major basal cerebral arteries. Transcranial color-coded duplex sonography identifies intracranial hemorrhage, cerebrovascular malformations and hydrocephalus but is inferior to neuroradiological techniques. It is likely that power Doppler sonography and transpulmonary contrast agents will provide an additional increase in diagnostic confidence of neurovascular ultrasonography. In the future, cerebral microemboli may become a marker for embolic activity of occlusive carotid artery and cardiac disease.

Carotid Stenosis↗
PubMed1996

Transcranial color-coded duplex sonography in unilateral flow-restrictive extracranial carotid artery disease.

PURPOSE: To provide transcranial color-coded duplex flow-velocity data for the basal cerebral arteries in patients with unilateral flow-restrictive extracranial carotid artery disease, and to compare these data with the flow velocities obtained in healthy control subjects. METHODS: Transcranial color-coded duplex sonography was performed in 78 patients with different patterns of cross flow through the anterior and posterior communicating arteries associated with unilateral obstruction (70% to 100%; 46 stenoses and 32 occlusions) of the internal carotid arteries. Peak systolic, mean, and end diastolic velocities were measured in the anterior, middle, and precommunicating and postcommunicating posterior cerebral arteries. These measurements were compared with the values obtained in 125 age- and sex-matched health control subjects. RESULTS: Patients with anterior communicating artery cross flow to the middle cerebral artery (63%) had increased peak velocity in the anterior cerebral artery and decrease peak velocity in the middle cerebral artery on the obstructed (ipsilateral) side, and increased peak velocity in the anterior cerebral artery on unobstructed (contralateral) side. Patients with anterior communicating artery cross flow to the pericallosal artery (19%) had increased contralateral peak systolic velocity and mean anterior cerebral artery velocities. Patients without anterior communicating artery cross flow (18%) had normal peak velocities in the anterior and middle cerebral arteries. Patients with posterior communicating artery cross flow (42%) had ipsilaterally decreased peak systolic and mean middle cerebral artery velocities and increased peak velocities in the precommunicating posterior cerebral artery. Patients without posterior communicating artery cross flow (58%) had ipsilaterally decreased peak systolic and mean middle cerebral artery velocities. CONCLUSION: Our findings suggest that typical abnormalities of basal cerebral artery flow velocities occur in patients with unilateral 70% to 100% obstruction of the internal carotid arteries resulting in different patterns of cross flow through the circle of Willis.

Adult↗
PubMed1995

Transcranial color-coded duplex sonography, magnetic resonance angiography, and computed tomography angiography: methods, applications, advantages, and limitations.

Transcranial color-coded duplex sonography (TCCD), magnetic resonance angiography (MRA), and computed tomography angiography (CTA) are novel noninvasive or minimally invasive techniques for the study of the intracranial circulation. TCCD is relatively inexpensive and permits bedside examination. It improves the accuracy and reliability of conventional transcranial Doppler studies. The main limitation of TCCD are the ultrasonic windows. They restrict the area of insonation to the major cerebral arteries and the proximal part of its branches, lower the spatial resolution, and may prevent transtemporal insonation. Using MRA, both large and small intracranial arteries and veins can be imaged by selecting the appropriate imaging parameters. MRA provides morphologic information about the cerebral vessels, relying on blood flow as the physical basis for generating contrast between stationary tissues and moving spins. MRA is highly sensitive for the detection of occlusive disease in large intracranial arteries. However, with bright blood techniques the degree of stenosis tends to be exaggerated. Flow direction, eg, in collaterals, can be determined by selective or phase-contrast MRA. Perfusion imaging techniques provide information about blood flow at the capillary level. Diffusion imaging depicts molecular motion. TCCD and MRA used in combination or alone may eliminate the need for intra-arterial digital subtraction angiography (DSA) in most patients studied for occlusive cerebrovascular disease. DSA may be reserved for those patients where there is disagreement among the noninvasive techniques, and for the diagnosis of cerebral aneurysms and arteriovenous malformations. CTA relies on spiral CT technology and intravenous contrast injection. To date, intracranial use has been predominantly for the diagnosis of aneurysms. The role of CTA for the detection of nonaneurysmal intracranial vascular disease has yet to be established.

Adult↗
PubMed1995

Cardiac myxomas: a long term study.

From 1980 to 1992 we followed 12 patients with cardiac myxomas for an average of 4.4 years (8 months-11 years). Presenting symptoms were neurological in four patients (hemiparesis, aphasia, visual field deficits, progressive dementia or vertigo), progressive dyspnoea in six, pulmonary embolism in one, and peripheral arterial or renal emboli in three. The diagnosis was suspected clinically in 11 patients. It was confirmed by echocardiography in ten and by thoracic CT in one. All these patients had cardiac surgery. One diagnosis was made at autopsy; the patient died unexpectedly during surgery for emboli to the leg arteries. At follow-up, two additional patients had died, one from myocardial infarction and one from rhabdomyosarcoma. Only one of the nine surviving patients had recurrent symptoms after cardiac surgery. His dementia continued to progress. The patients without new symptoms after cardiac surgery had normal MRI of the brain or residual ischaemic lesions. MRI of the patient with progressive dementia showed multiple cerebral lesions with a bright centre and a dark rim on T1- and T2-weighted spin-echo images. On CT there were many calcified lesions. CT, MR angiography and contrast angiography revealed multiple fusiform aneurysms. The rare occurrence of progressive neurological symptoms after myxoma resection with multiple cerebral lesions and aneurysms should suggest myxoma metastases to the brain.

Adult↗
PubMed1995

Transient cerebral circulatory arrest coincides with fainting in cough syncope.

During prolonged coughing, intrathoracic and intra-abdominal pressures are transmitted via the great veins to the intracranial compartment, causing transient elevated intracranial pressure. The resulting reduction of cerebral perfusion pressure may cause a critical impairment of cerebral blood flow (CBF). Obstructive airway disease seems to be a prerequisite to build up the intrathoracic and intracranial pressures to a degree sufficient to compromise CBF and cause cough syncope. Using transcranial Doppler sonography (TCD) monitoring of middle cerebral artery flow velocities, we studied three patients with cough syncope. During coughing, they showed a transient cerebral circulatory arrest, which coincided with loss of consciousness in the two patients who fainted during TCD monitoring. EEG showed slowing, heart rate increased, and systemic arterial BP in one patient was preserved during the syncope. Our findings support the hypothesis that a critical reduction of CBF causes cough syncope.

Cerebral Arteries↗
PubMed1995

Ultrasound findings in carotid artery dissection: analysis of 43 patients.

BACKGROUND AND PURPOSE: To analyze the value of ultrasound for early diagnosis and follow-up of internal carotid artery dissection. METHODS: The carotid arteries were evaluated in 43 consecutive patients using extracranial and transcranial pulsed-wave Doppler and duplex sonography. RESULTS: Ultrasound examination was performed, on average, 7.7 days after the first symptoms. The dissections subsequently were verified by MRI (16 patients), angiography (13 patients), or both (14 patients) on average 4.4 days later. The overall sensitivity of the combined examination was 95% (93% for extracranial Doppler, 86% for transcranial Doppler, and 79% for duplex sonography). All three methods detected occlusions or high-grade stenoses in 100% of patients and moderate- or low-grade stenoses in 80% (combined methods), 70% (extracranial Doppler), 40% (transcranial Doppler), and 20% (duplex) of the patients. The findings in 33 patients with an occlusion or high-grade stenosis according to neuroradiology were as follows: absent flow signal in the internal carotid artery (100%) and biphasic (stump) flow in its bulb (86%), high-resistance flow pattern of the ipsilateral common carotid artery (91%), signs of collateral flow across the circle of Willis (97%), and low flow in the middle cerebral artery (79%) on transcranial insonation. In seven patients, a moderate stenosis of the high cervical carotid segment was found because of a retromandibular high-velocity signal. In five of them this was the only abnormal finding. Duplex examination was helpful because it confirmed absent internal carotid artery flow or stump flow in the case of occlusion or high-grade stenosis (100%) and excluded an atherosclerotic origin by demonstrating a patent bulb (100%) and the absence of plaques (95%). Follow-up studies showed recanalization in 63% of patients, occurring at variable intervals. Occlusion persisted in 37%. CONCLUSIONS: Ultrasound performed within the first weeks can corroborate a clinically suspected carotid dissection in up to 95% of patients. Repetitive follow-up studies in most cases are sufficient to monitor evolution.

Adult↗
PubMed1994

A validation study on the intraobserver reproducibility of transcranial color-coded duplex sonography velocity measurements.

Transcranial color-coded duplex sonography (TCCD) is a new method for the measurement of angle-corrected intracranial blood velocities. The insonation angle represents the most important technical variable affecting Doppler velocimetry. The present study was designed to evaluate the intraobserver reproducibility of TCCD for repeated examinations of blood velocity in the anterior, middle and posterior cerebral, basilar and vertebral arteries. Three examinations were performed by the same examiner in each of 20 healthy volunteers within 10 days, with a minimal interval of 2 days between two subsequent examinations. The observer was blinded to previous results. The reproducibility was evaluated by calculating the correlation coefficient (r) and the coefficient of variance (CV) of the difference between the values obtained from the second and the third examination vs. the first examination. The results showed good reproducibility of TCCD velocity measurements in all examined arteries: for maximal systolic velocity r was 0.80-0.94 (p < 0.001), and CV was 5.5-9.4%; for maximal end-diastolic velocities r was 0.89-0.94 (p < 0.001), and CV was 6.6-12.2%.

Adult↗
PubMed1994

Role of impaired CO2 reactivity in the diagnosis of cerebral low flow infarcts.

Previous studies on CO2 reactivity in cerebral low flow infarcts (LFIs) included patients with lesions in the frontoparasagittal area, supraganglionic white matter, and temporoparieto-occipital zone. Supraganglionic white matter LFIs are, however, difficult to separate from non-low flow induced infarcts of the lacunar type, and temporoparieto-occipital LFIs from infarcts in the territory of the inferior stem of the middle cerebral artery. The CO2 reactivity of the middle cerebral artery was studied in 56 patients with high grade stenoses and occlusions of the internal carotid artery and LFIs (n = 9) in the frontoparasagittal border zone, territorial infarcts (n = 26), no infarcts (n = 21), and normal subjects (n = 25) by means of transcranial Doppler sonography. The aim was to investigate whether patients with LFIs have significantly lower CO2 reactivity than patients with territorial infarcts, no infarcts, and normal subjects. Patients with LFIs had the most severely reduced CO2 reactivity on the symptomatic side and CO2 reactivity was significantly lower than on the asymptomatic side. It was also lower than in patients with unilateral and bilateral internal carotid artery obstructions and territorial infarcts, asymptomatic patients, and healthy volunteers. It is concluded that LFIs are associated with significantly reduced CO2 reactivity.

Adult↗
PubMed1994

Transcranial color-coded duplex sonography in cerebral aneurysms.

BACKGROUND AND PURPOSE: Diagnosis and successful therapy before rupture of cerebral aneurysms would be most desirable in view of the high mortality and morbidity rates of aneurysmal subarachnoid hemorrhage. Using transcranial color-coded duplex sonography, we studied radiologically proven cerebral aneurysms to define ultrasonographic criteria and sensitivity for their diagnosis and detection. METHODS: Twenty-nine consecutive patients with 30 radiologically proven cerebral aneurysms were prospectively examined using transcranial color-coded duplex sonography. The sonographer was aware of cerebral computed tomographic and magnetic resonance imaging findings but was blinded to the results of cerebral angiography. RESULTS: Ultrasonographic findings for aneurysms studied were as follows: (1) Scanning planes that transsected approximately mid-aneurysm showed a round or oval mass that was divided by a "separation zone" into red and blue areas. (2) The "separation zone" was characterized by dark or no colors. (3) Peripheral scanning planes showed monochromatic images. (4) No turbulence was found. (5) No spontaneous fluctuations were detected. Twenty-three of 27 (85%) nonthrombosed aneurysms with a diameter of 6 to 25 mm were identified. The walls and three thrombosed and four nonthrombosed aneurysms (mean diameter, 5 mm) were missed. CONCLUSIONS: Transcranial color-coded duplex sonography can provide the diagnosis of nonthrombosed aneurysm using the above-cited criteria because of its capacity to reveal flow phenomena. It is not the method of choice in the search for aneurysms because small and thrombosed aneurysms are missed. Careful visual inspection of the intracranial arteries to permit incidental detection of cerebral aneurysms should be part of every transcranial color-coded duplex examination.

Adolescent↗
PubMed1994

Enhanced cerebral blood flow in acute mountain sickness.

Mean blood flow velocity (v) of both middle cerebral arteries (MCA) was assessed by transcranial Doppler sonography (TCD) in 23 subjects at an altitude of 490 m, as well as after a rapid ascent to a high altitude research laboratory at 4559 m, and daily during a continued 72-h stay at this altitude. Relative changes of mean blood flow velocities (v) of both MCA at high altitude were expressed as percentages of low altitude values and correlated with the development of signs and symptoms of acute mountain sickness (AMS) and changes of arterial PO2, PCO2, and hemoglobin. After ascent to 4559 m, overall MCA-v (mean of all measurements obtained in each subject at high altitude) increased significantly to 148 +/- 16% of baseline values in the subjects with AMS (AMS+) and to 127 +/- 24% in the subjects without AMS (AMS-) (mean +/- SD). This v increase was higher in subjects with AMS and reached statistical significance on day 1 (+50 +/- 19%) and on day 2 (+48 +/- 23%) as compared to the healthy subjects (+27 +/- 24% and +21 +/- 26% on days 1 and 2, respectively). The rise of MCA-v correlated inversely with arterial PO2 on days 2 (r = -0.62, p < 0.005), 3 (r = -0.67, p < 0.025) and 4 (r = -0.69, p < 0.025) and from days 1 to 4 (r = -0.51, p < 0.001). MCA-v did not correlate with blood pressure, arterial PCO2 or hemoglobin. Our results suggest that subjects with AMS have a higher MCA-v increase due to a lower arterial PO2 than healthy subjects.

Acute Disease↗