PubMed Health⌕ Search

Biomedical subjects

R W Baumgartner

Publications and source records attributed to R W Baumgartner.

At least 55 records · Page 3Linked to original sources
PubMed1999

Transcranial color-coded duplex sonography.

Transcranial color-coded duplex sonography (TCCS) enables the reliable assessment of intracranial stenoses, occlusions, and cross-flow through the circle of Willis without using potentially hazardous compression tests. Transpulmonary ultrasound contrast agents (UCAs) increase the number of conclusive TCCS investigations, which suggests that UCAs may provide the conclusive evaluation of intracranial arteries in most patients with ischemic cerebrovascular disease. Further, contrast-enhanced TCCS may become an important tool both for the management of acute ischemic stroke by assessing intracranial hemodynamics and the displacement and diameter changes in supratentorial ventricles. TCCS is useful for the detection and monitoring of intracranial vasospasm, may visualize larger supratentorial hematomas with subcortical location and hemorrhagic transformation of ischemic infarcts, and provides the incidental detection of cerebral aneurysms and arteriovenous malformations. Second-generation UCAs and new ultrasound machines are very likely to further increase the frequency of conclusive TCCS studies. Power-based three-dimensional, contrast-enhanced TCCS is an important further development, which would make the method much less operator dependent. Site-targeted UCAs appear to provide a new and exciting method for ultrasonic diagnosis and management of patients with ischemic cerebrovascular disease.

Arteriovenous Malformations↗
PubMed1999

A validation study on the intraobserver and interobserver reproducibility of renal artery duplex ultrasound.

Aim of the present study was to evaluate intraobserver and interobserver reproducibility of direct renal artery Doppler velocimetry. Healthy volunteers were evaluated by one examiner on three separate occasions and by three different examiners in a single day. Peak systolic velocities of the aorta (PSV.Ao) and proximal renal arteries (PSV.RA) were taken at an optimal angle below 60 degrees. The renal-to-aortic ratio (RAR) was calculated dividing PSV.RA by PSV.Ao. Mean values +/- 2 SD were 85 +/- 34 (49-150) cm/s for the PSV.RA, 38 +/- 20 (0-60 degrees) for the Doppler angle of insonation, 102 +/- 37 (63-153) cm/s for the PSV.Ao, and 0.85 +/- 0.41 (0.49-1.58) for the RAR. Correlation coefficients and coefficient of variation were 0.64-0.82/7.8%-10.1% (PSV.RA), 0.75-0.82/9.9%-13.8% (RAR) for intraobserver evaluations; and 0.79-0.80/7.7%-12.5% (PSV-RA), 0.65-0.78/9.5%-12.3% (RAR) for interobserver evaluations. Reliable results of direct renal artery Doppler velocimetry confirm clinical applicability and suitability for repeated measurements after catheter-based interventions or surveillance of low-grade stenoses.

Adult↗
PubMed1999

Acute mountain sickness is not related to cerebral blood flow: a decompression chamber study.

To evaluate the pathogenetic role of cerebral blood flow (CBF) changes occurring before and during the development of acute mountain sickness (AMS), peak mean middle cerebral artery flow velocities () were assessed by transcranial Doppler sonography in 10 subjects at 490-m altitude, and during three 12-min periods immediately (SA1), 3 (SA2), and 6 (SA3) h after decompression to a simulated altitude of 4,559 m. AMS cerebral scores increased from 0. 16 +/- 0.14 at baseline to 0.44 +/- 0.31 at SA1, 1.11 +/- 0.88 at SA2 (P < 0.05), and 1.43 +/- 1.03 at SA3 (P < 0.01); correspondingly, three, seven, and eight subjects had AMS. Absolute and relative at simulated altitude, expressed as percentages of low-altitude values (%), did not correlate with AMS cerebral scores. Average % remained unchanged, because % increased in three and remained unchanged or decreased in seven subjects at SA2 and SA3. These results suggest that CBF is not important in the pathogenesis of AMS and shows substantial interindividual differences during the first hours at simulated altitude.

Acute Disease↗
PubMed1999

Assessment of >/=50% and <50% intracranial stenoses by transcranial color-coded duplex sonography.

BACKGROUND AND PURPOSE: A favorable risk-benefit ratio for warfarin compared with aspirin has been reported for the prevention of major vascular events in symptomatic >/=50% intracranial stenoses. Transcranial color-coded duplex sonography (TCCS) criteria providing an accurate detection of >/=50% and <50% stenoses of the anterior, middle, and posterior cerebral arteries and basilar and vertebral arteries were evaluated retrospectively with angiography used as the standard of reference. METHODS: Prospectively collected TCCS, extracranial color-coded duplex sonography, and intra-arterial digital subtraction angiography data of 310 patients were reviewed. The patients had angiography for confirmation of symptomatic extracranial >/=70% carotid stenoses, symptomatic stenoses (peak systolic velocity higher than the corresponding mean value +2 SDs of 104 normal subjects), and occlusions of the middle cerebral or basilar artery previously assessed by ultrasound. The sonographer was not aware of angiographic findings. RESULTS: TCCS would have detected all 31 of >/=50% intracranial stenoses with 1 false-positive and 35 of 38 <50% stenoses with 3 false-positives. One of 69 stenoses (1%) and 280 of 2741 normal arteries (10%) were missed because of inadequate insonation windows. The corresponding peak systolic velocity cutoffs for >/=50%/<50% stenoses were >/=155/>/=120 cm/s (anterior cerebral artery), >/=220/>/=155 cm/s (middle cerebral artery), >/=145/>/=100 cm/s (posterior cerebral artery), >/=140/>/=100 cm/s (basilar artery), and >/=120/>/=90 cm/s (vertebral artery). CONCLUSIONS: TCCS may reliably assess >/=50% and <50% basal cerebral artery narrowing and prove useful for noninvasive management of patients with symptomatic intracranial stenoses.

Adult↗
PubMed1999

Persistent Klüver-Bucy syndrome after bilateral thalamic infarction.

OBJECTIVE: To describe a patient who exhibited a partial Klüver-Bucy syndrome after small bilateral ischemic lesions in the thalami. BACKGROUND: Previously reported patients with Klüver-Bucy syndrome had very large, mostly bilateral lesions in the limbic system and could not provide sufficient information about its anatomo-functional correlate. METHOD: Behavioral assessments and clinical examinations, including magnetic resonance imaging and positron emission tomography, were conducted. RESULTS: The patient was severely amnestic, distractible, hyperoral, and affectively dyscontrolled, and she behaved socially inappropriately. Magnetic resonance imaging showed bilateral infarctions in the territories of both thalamoperforating arteries, and positron emission tomography revealed bilaterally decreased fluorodeoxyglucose uptake in the anterior parts of the ventral thalami and, to a lesser extent, in the fronto-temporal cortices. CONCLUSIONS: This behavioral syndrome has not yet been reported with isolated diencephalic lesions, but it has been observed after bilateral temporal lobe lesions. The authors conjecture that this syndrome resulted from a disruption of the pathways connecting the dorsomedial thalami with the prefrontal cortices and with other limbic areas, systems essential for memory and the regulation of impulses and emotions.

Aged↗
PubMed1998

[Acute therapy of ischemic stroke].

Ischemic stroke is a neurological emergency as transition form reversible to irreversible lesions of the brain may be prevented by starting the therapy within six hours after the onset of the neurological deficits. Intravenous thrombolysis may be administered within the first three hours and intraarterial thrombolysis within the first six hours after considering inclusion and exclusion criteria. Neuroprotective drugs are under investigation and may enlarge the spectrum of acute therapy in the near future. Ischemic strokes that do not qualify for thrombolysis may be treated with unfractionated heparin, aspirin or low-molecular weight heparin. Indications for the administration of antithrombotic drugs are discussed. Blood pressure is frequently elevated in acute ischemic stroke, but rarely needs therapy or careful lowering. Fever, hypo- und hyperglycemia, epileptic seizures and intracranial hypertension should be treated.

Acute Disease↗
PubMed1998

Further evidence of gaseous embolic material in patients with artificial heart valves.

OBJECTIVE: We undertook this study to evaluate the hypothesis that most microemboli signals in patients with artificial heart valves are gaseous, assuming that microemboli counts in cerebral arteries would progressively decline with increasing distance from the generating heart valve. METHODS: A total of 10 outpatients with CarboMedics (Sulzer Carbomedics Inc., n = 5) and ATS prosthetic heart valves (n = 5) in the aortic (n = 8), mitral (n = 1), or both aortic and mitral positions (n = 1) were recruited. Monitoring was performed simultaneously over the middle and anterior cerebral arteries and the common carotid artery for 30 minutes with the 2 MHZ transducers of a color duplex scanner (common carotid artery) and pulsed-wave Doppler ultrasonography (intracranial arteries). All data were harvested in an eight-channel digital audio tape recorder, and microembolic signal counts were evaluated online by two separate observers. RESULTS: Significantly higher microembolic signal counts were recorded in the common carotid artery (112 [75 to 175]) compared with the middle and anterior cerebral arteries (30 [18 to 36], p < 0.0001). Interobserver variability was satisfactory (k = 0.81). CONCLUSIONS: Our results strongly argue for gaseous underlying embolic material in patients with artificial heart valves because bubbles are bound to implode with time.

Adult↗
PubMed1998

Vasomotor reactivity is exhausted in transient ischaemic attacks with limb shaking.

OBJECTIVES: To investigate cerebral vasomotor reactivity in five patients with limb shaking transient ischaemic attacks by using transcranial Doppler sonography. METHOD: Attacks with transient limb shaking were unilateral in four patients and bilateral in one. Internal carotid arteries on the side opposite the abnormal limb movements showed three 90-95% stenoses and three occlusions as assessed by cerebral angiography in three and magnetic resonance angiography and ultrasound in one case each. Reactivity of cerebral resistance vessels was studied by measuring peak mean velocities in the middle cerebral artery (MCA) before and after the application of CO2 enriched air. Reference values were obtained from 25 normal subjects. RESULTS: During hypercapnia peak mean velocities slightly decreased in five MCAs (steal phenomenon) and remained unchanged in one MCA opposite the abnormal movements, whereas the other MCAs showed normal reactivities. CONCLUSION: The delineation of an exhausted cerebral vasoreactivity in all hemispheres opposite the involuntary limb movements suggests that haemodynamic failure is the cause of transient ischaemic attacks with limb shaking.

Aged↗
PubMed1998

Selective intra-arterial fibrinolysis of acute central retinal artery occlusion.

BACKGROUND AND PURPOSE: Occlusion of the central retinal artery (CRAO) causes a sudden decrease of monocular vision. Because early restoration of blood flow may improve outcome, we attempted to treat CRAO with selective intra-arterial fibrinolysis. METHODS: Intra-arterial fibrinolysis was performed within 6 hours after symptom onset in 17 patients with thromboembolic CRAO. Symptoms were painless, acute and severe decrease of vision. Urokinase (100 000 to 900 000 IU) was given through a microcatheter into the ophthalmic artery over 10 to 90 minutes. For comparison, the history and visual outcome of 15 control patients who did not receive fibrinolytics were evaluated. In both groups some of the patients underwent paracentesis and/or received carboanhydrase inhibitors. RESULTS: Patients who underwent fibrinolysis fared better than control patients (P=0.01). Three patients (17.6%) recovered completely after fibrinolysis and regained visual acuity of 20/20 (n=2) to 25/20 (n=1). Two additional patients (11.8%) showed a marked improvement to a visual acuity of 20/30. In 6 patients (35. 3%) vision improved slightly. They were able to count fingers, detect hand movements, or perceive light. In 6 patients (35.3%), fibrinolytic treatment was without effect. Among control patients, 1 patient (6.7%) showed partial, 4 patients (26.7%) minimal, and 10 (66.7%) no improvement of vision. CONCLUSIONS: A complete or marked improvement of visual acuity was achieved in one third of intra-arterial fibrinolysis patients but in none of the control patients. Intra-arterial fibrinolysis seems to have the potential to "lighten" the spontaneously poor outcome of CRAO.

Acute Disease↗
PubMed1998

MR angiography with ultrashort echo time in cerebral aneurysms treated with Guglielmi detachable coils.

We evaluated a time-of-flight three-dimensional MR angiographic sequence with an ultrashort echo time for its ability to characterize the perfusional state of cerebral aneurysms that had been treated with Guglielmi detachable coils and to depict adjacent cerebral arteries. The results were compared with findings at conventional MR angiography and digital subtraction angiography. Adjacent vessels were seen better in 36% of patients imaged with the new technique. Both MR angiographic methods detected residual cerebral aneurysmal perfusion with a tendency to overestimate the patent portion of the aneurysm.

Adult↗
PubMed1997

Nontraumatic spinal epidural hematomas. MR features.

PURPOSE: Spinal epidural hematoma (SEH) is a rare clinical entity with a bleak outcome. The aim of our study was to establish the value of MR findings in the diagnosis of nontraumatic SEH. MATERIAL AND METHODS: Seven patients with nontraumatic SEH were examined by MR at 1.5 T. Two patients were under anticoagulation therapy with heparin, and 2 others were taking salicylic acid. One patient had lupus erythematodes with a marked thrombocytopenia. One patient had a spinal arteriovenous malformation. RESULTS: MR imaging permitted the accurate localization of extradural intraspinal expansive lesions which exhibited the characteristic signal intensities of blood. Five patients underwent laminectomy and evacuation of the hematoma. In the acute phase, the hematomas appeared isointense when compared with the spinal cord on T1-weighted images and hyperintense on T2-weighted images. Later the hematomas were hyperintense on T1-weighted images and showed signals identical to those of cerebrospinal fluid (CSF) on T2-weighted images. CONCLUSION: MR imaging established the exact diagnosis and localization of SEH in all cases. MR also can provide useful information about the age of the hematomas.

Acute Disease↗
PubMed1997

Contrast-enhanced transcranial color-coded duplex sonography in ischemic cerebrovascular disease.

BACKGROUND AND PURPOSE: Echo contrast agents have been shown to provide conclusive examinations in most patients with insufficient ultrasound penetration through the temporal bone. We investigated the diagnostic value of contrast-enhanced (CE) transcranial color-coded duplex sonography (TCCD) in patients with ischemic cerebrovascular disease and insufficient temporal windows and evaluated TCCD criteria that predict whether CE-TCCD studies may become conclusive. METHODS: Thirty-three patients presenting with ischemic strokes (n = 21) and transient ischemic attacks (n = 12) were investigated. Extracranial color duplex imaging showed normal findings in 24 patients, eight > or = 70% stenoses and one occlusion of the carotid arteries in 8 patients, and severe occlusive disease of both vertebral arteries in 1 patient. Seven carotid stenoses and vertebral artery obstructions were confirmed by angiography. The galactose/palmitic acid-based echo contrast agent was injected intravenously as bolus of 200, 300, or 400 mg/mL in a dosage of 10, 5, and 5 mL, respectively. RESULTS: Thirty-two of the 33 patients were completely examined because 1 patient who felt pain at the injection site declined further investigations. Twenty-one (66%) of 32 CE studies were conclusive and showed cross-flow through three anterior and two posterior communicating arteries, but no stenoses and occlusions. Precontrast identification of any cerebral artery provided an overall accuracy of 97% in predicting a conclusive CE investigation. Precontrast TCCD identified no arterial Doppler signals in patients with inconclusive CE studies. CONCLUSIONS: CE-TCCD provided conclusive examinations in two thirds of patients with ischemic cerebrovascular disease and ultrasound-refractory temporal windows. Precontrast detection of any cerebral artery reliably predicted a conclusive CE investigation.

Adult↗
PubMed1997

Transoccipital power-based color-coded duplex sonography of cerebral sinuses and veins.

BACKGROUND AND PURPOSE: Power-based transcranial color-coded duplex sonography is a new development for cerebrovascular imaging that is suited for detection of slow velocities. The purpose of this study was to evaluate the ability of this technique to detect cerebral sinuses and veins by means of the occipital window and to provide reference data. METHODS: The straight and inferior sagittal sinuses, great and internal cerebral veins, and basal veins were insonated in 120 normal subjects. The number of identified vessels, peak systolic (PSV) and end-diastolic (PDV) velocities, and resistance indices were determined. RESULTS: In subjects aged 20 to 59 years, straight sinuses were identified in 81% and great and internal cerebral veins in 34%. In subjects aged 60 to 79 years, straight sinuses were detected in 50%, great cerebral veins in 20%, and internal cerebral veins in 13%. All insonated inferior sagittal sinuses and basal veins were missed. Velocities were highest in straight sinuses (PSV, 35 [7 to 64] cm/s; PDV, 23 [2 to 43] cm/s), slower in great cerebral veins (PSV, 23 [12 to 34] cm/s; PDV, 16 [7 to 26] cm/s), and slowest in internal cerebral veins (PSV, 14 [10 to 18] cm/s; PDV, 10 [5 to 15] cm/s) (mean with 95% confidence intervals [CIs]). Straight sinus velocities decreased with age for PSV (20 to 39 years, 40 [7 to 73] cm/s; 60 to 79 years, 28 [9 to 46] cm/s; P < .01) and PDV values (20 to 39 years, 28 [4 to 52] cm/s; 60 to 79 years, 16 [5 to 26] cm/s; P < .001) (mean with 95% CIs) and were higher in women than men in the group aged 20 to 39 years. (P < .05). Resistance indices increased with age in the straight sinus (20 to 39 years, 0.30 [0.18 to 0.42]; 60 to 79 years, 0.42 [0.31 to 0.53]; P < .001) (mean with 95% CIs). CONCLUSIONS: Transoccipital power-based color-coded duplex sonography enabled imaging and velocity measurements in the straight sinus of subjects aged 20 to 59 years. In elder subjects detection rate of the straight sinus decreased, and it was low for deep cerebral veins in all age groups.

Adult↗
PubMed1997

Transcranial color-coded duplex sonography in the evaluation of collateral flow through the circle of Willis.

PURPOSE: To determine the sensitivity, specificity, and positive and negative predictive values of transcranial color-coded duplex sonographic (TCCD) evaluation of cross flow through the anterior (ACoA) and posterior (PCoA) communicating arteries in patients with occlusive cerebrovascular disease. METHODS: We studied prospectively 132 patients (37 women, 95 men; mean age, 60 years) with stenoses of more than 69% reduction in vessel diameter (n = 93) and occlusions (n = 52) of the internal carotid artery, and three occlusions of the basilar artery. The sonographer was aware of extracranial sonographic findings but was blinded to the results of cerebral angiography. RESULTS: Nine patients (7%) with thick bones preventing transtemporal insonation and three patients (3%) with occlusions of the middle (n = 3) and anterior (n = 1) cerebral arteries were excluded. Sensitivity of TCCD for detection of collateral flow through the ACoA in patients with occlusive carotid artery disease was 98%, specificity was 100%, positive predictive value was 100%, and negative predictive value was 98%. The corresponding values for the PCoA were 84%, 94%, 94%, and 84%, respectively. All three functional PCoAs were identified in patients with occluded basilar arteries. CONCLUSION: TCCD is a valuable method for noninvasive evaluation of cross flow through the ACoA in patients with adequate sonographic windows. However, TCCD evaluation of cross flow through the PCoA is less reliable, because hemodynamic criteria may cause falsely positive and falsely negative results.

Adult↗
PubMed1997

[History of neurovascular ultrasonography].

History of diagnostic ultrasound begins with the Austrian physicist Christian Doppler, who described in 1842 the Doppler principle. 40 years later, the Curies discovered the reverse piezoelectric effect that produces ultrasound. The first ultrasonic devices were designed at the beginning of the 20th century and were used among other things for detection of submarines. Development during World War II permitted the construction of the first transcranial (1940) and extracranial (1949) ultrasound imaging units. Continuous-wave Doppler sonography was introduced in clinical practice 20 to 30 years later. Due to its high validity, this technique has become the standard method for evaluation of extracranial occlusive cerebrovascular disease. Further ultrasonic developments like duplex and color duplex sonography have increased the diagnostic possibilities but did not replace continuous-wave sonography in many European ultrasound laboratories. Transcranial ultrasound studies are performed by means of pulsed-wave Doppler or color duplex sonography. It is likely that power Doppler and transpulmonary contrast agents will further increase diagnostic confidence in neurovascular ultrasound. The search for a source of arterio-arterial embolism in case of ocular and cerebral ischemia remains the main indication for neurovascular ultrasonography. Additional indications are repetitive studies in dissection, vasospasm, endovascularly treated vascular malformations and stenoses, intracranial pressure monitoring, examination of cerebrovascular reactivity in suspicion of hemodynamic ischemia, and diagnostic work-up of cough syncope, pulsatile tinnitus and cardiac right-left shunt.

Central Nervous System↗
PubMed1997

Transtemporal power- and frequency-based color-coded duplex sonography of cerebral veins and sinuses.

PURPOSE: To determine the ability of transtemporal power- and frequency-based transcranial color-coded duplex sonography to aid in the assessment of cerebral veins and sinuses, as well as to provide reference data for flow direction and velocity. METHODS: Using a color duplex device equipped with a 2.0/2.5-MHz sector scan, we insonated 120 healthy volunteers and three patients with cerebral venous thrombosis. RESULTS: In subjects 20 to 59 years old, deep middle cerebral veins were identified in 88%, basal veins in 97%, straight sinuses in 60%, and transverse sinuses in 42%. The corresponding values for subjects 60 to 79 years old were 53%, 86%, 23%, and 20%, respectively. Velocities were highest in transverse and straight sinuses, slower in basal veins, and slowest in deep middle cerebral veins. Flow was directed lateromedially in the deep middle cerebral vein, rostrocaudally in the basal vein and straight sinus, and mediolaterally in the transverse sinus. Two patients with straight sinus thromboses showed reversed flow direction in the basal veins, and one patient with superior sagittal sinus thrombosis showed elevated velocities in a deep middle cerebral vein. CONCLUSION: Transtemporal power- and frequency-based color-coded duplex sonography enabled imaging and velocity measurements in deep cerebral veins in subjects 20 to 59 years old, but detection of the straight and transverse sinuses was low. In older subjects, only the basal vein was regularly assessed.

Adult↗
PubMed1996

Diagnostic criteria for transcranial colour-coded duplex sonography evaluation of cross-flow through the circle of Willis in unilateral obstructive carotid artery disease.

A transcranial colour-coded duplex sonography (TCCD) study was performed to establish reliable criteria for the assessment of collateral flow through the anterior (ACoA) and posterior (PCoA) communicating artery without using compression tests. We studied 86 patients with angiographically evaluated unilateral > 69% stenosis (n = 53) and occlusion (n = 33) of the carotid artery. The following TCCD criteria were evaluated: for diagnosis of cross-flow through the ACoA, detection of reversed flow in the anterior cerebral artery (ACA) on the obstructed (ipsilateral) side. For the diagnosis of cross-flow through the PCoA: (A) identification of the PCoA; (B) peak systolic velocity in P1 posterior cerebral artery (PCA) higher than the mean value + 2 SD of normals; (C) ratio of ipsilateral peak systolic P1 PCA velocity to peak systolic P1 PCA velocity to peak systolic P2 PCA velocity higher than the mean ratio + 2 SD of normals; (D) ratio of ipsilateral peak systolic P1 PCA velocity to contralateral peak systolic P1 PCA velocity higher than the mean ratio + 2 SD of normals; (E) peak systolic basilar artery velocity higher than the mean value + 2 SD of normals. Eight patients (9%) with inadequate temporal ultrasonic windows were excluded. The sensitivity and specificity for TCCD evaluation of ACoA cross-flow were 100%. Using criteria A and B the corresponding values for the PCoA were 85 and 98%, respectively. Criteria C-E were not useful owing to lower sensitivity. In conclusion, we delineated TCCD criteria that make it possible to assess reliably the cross-flow through the circle of Willis in patients with adequate ultrasonic windows.

Adult↗