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Biomedical subjects

R W Baumgartner

Publications and source records attributed to R W Baumgartner.

At least 19 recordsLinked to original sources
PubMed2001

Carotid dissection with and without ischemic events: local symptoms and cerebral artery findings.

OBJECTIVE: To study whether spontaneous dissections of the cervical internal carotid artery dissection (ICAD) with and without ischemia of the brain or retina differ in the prevalence of vascular risk factors, local neurologic signs and symptoms, and stenoses and occlusions of the cerebral arteries. METHODS: The authors prospectively studied 181 consecutive patients with 200 ICAD. Diagnosis was based on ultrasonography and MRI or catheter angiography. Vascular risk factors, presenting local (headache, neck pain, Horner syndrome, pulsatile tinnitus, cranial nerve palsy on the side of the ICAD) and ischemic signs and symptoms, and ultrasonographic findings in the carotid and basal cerebral arteries were evaluated. RESULTS: ICAD with ischemic events (n = 145) had a higher prevalence of hypercholesterolemia (p < 0.05), >80% stenoses and occlusions of the ICA (p < 0.0001), and intracranial obstructions (p < 0.001). ICAD without ischemic events (n = 55) had a higher prevalence of Horner syndrome (p < 0.001), cranial nerve palsy (p < 0.01), and normal ICA findings (p < 0.0001). CONCLUSIONS: These data suggest that ICAD causing high-grade stenosis and occlusion are more likely to lead to intracranial obstructions and cerebral or retinal ischemic events. Conversely, ICAD without luminal narrowing cause more local signs and symptoms.

Adolescent↗
PubMed2001

Stroke in hemoglobin (SD) sickle cell disease with moyamoya: successful hydroxyurea treatment after cerebrovascular bypass surgery.

An 11-year-old boy with hemoglobin sickle disease (HbSD), bilateral stenosis of the intracranial carotid arteries, and moyamoya syndrome had recurrent ischemic strokes with aphasia and right hemiparesis. His parents (Jehovah's Witnesses) refused blood transfusions. After bilateral extracranial-intracranial (EC-IC) bypass surgery, hydroxyurea treatment increased hemoglobin F (HbF) levels to more than 30%. During a follow-up of 28 months, flow velocities in the basal cerebral arteries remained stable, neurologic sequelae regressed, and ischemic events did not recur. This is the first report of successful hydroxyurea treatment after bypass surgery for intracranial cerebral artery obstruction with moyamoya syndrome in sickle cell disease. The patient's religious background contributed to an ethically challenging therapeutic task. (Blood. 2001;97:2165-2167)

Anemia, Sickle Cell↗
PubMed2001

A survey of neuroimaging research in European neurological departments.

In the international neurological literature, neuroimaging research plays an important role. Neuroimaging techniques are also of steadily increasing importance for clinical diagnosis and treatment monitoring. Therefore, neuroimaging research activities were surveyed by a questionnaire, which was completed by 100 neurological centres across Europe. It showed that most groups use magnetic resonance imaging (MRI), fMRI, computerized tomography (CT) and single photon emission computerized tomography (SPECT). Positron emission tomography (PET) and ultrasound are also employed by nearly half of the centres. Neuroimaging research involves co-operation amongst typically five to 10 disciplines. Cerebrovascular disease, dementia, cognitive disorders, epilepsy, movement disorders, brain tumours and multiple sclerosis are frequently being studied. Many groups rely on small budgets, have few full-time scientists and limited access to expensive resources. There is little exchange of scientists amongst laboratories. It was felt that funding and co-operation needed improvement in order to maintain a high standard in neuroimaging research.

Data Collection↗
PubMed2001

Microembolic signal counts increase during hyperbaric exposure in patients with prosthetic heart valves.

BACKGROUND: Patients with prosthetic heart valves have an increased risk of thromboembolic events, and transcranial Doppler sonography reveals microembolic signals. Whereas microembolic signals were initially assumed to be of particulate matter, recent studies suggest that they are partially gaseous in origin. If this is true, alteration of environmental pressure should change microembolic signal counts. We undertook this study to evaluate the influence of hyperbaric exposure on microembolic signal counts in persons with prosthetic heart valves. METHODS AND RESULTS: Microembolic signal counts were monitored by transcranial Doppler sonography of both middle cerebral arteries under normobaria (normobaria 1), 2 subsequent periods of hyperbaria (2.5 and 1.75 bar), and a second period of normobaria (normobaria 2) in 15 patients with prosthetic heart valves. Each monitoring period lasted 30 minutes. Compression and decompression rates were 0.1 bar/min. Microembolic signal counts increased from 20 (12-78) at normobaria 1 to 79 (30-165) at 2.5 bar (P <.01 vs normobaria 1 and 2), decreased to 44 (18-128) at 1.75 bar (P <.01 vs normobaria 1 and 2.5 bar; P <.001 vs normobaria 2), and returned to 20 (8-96) at normobaria 2 (values are medians and 95% confidence intervals). CONCLUSIONS: Our results strongly suggest that gaseous bubbles are underlying material for part of the microembolic signals detected in patients with prosthetic heart valves.

Aortic Valve↗
PubMed2001

Influence of positive end-expiratory pressure on intracranial pressure and cerebral perfusion pressure in patients with acute stroke.

BACKGROUND AND PURPOSE: We undertook this study to evaluate the influence of positive end-expiratory pressure (PEEP) on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in patients with acute stroke. METHODS: A total of 20 ventilated patients of a neurological intensive care unit were examined under a protocol entailing variation of PEEP to 4, 8, 12, and 4 mm Hg; mean arterial blood pressure (MAP), ICP, heart rate, and mean velocity of the middle cerebral arteries (V(m) MCA) were recorded. RESULTS: CPP significantly changed depending on the various PEEP levels. No significant differences in remaining parameters were evident. Three distinct reaction patterns of the parameters monitored were observed: (1) All parameters remained stable through the various PEEP levels (15 patients, 40 examinations). (2) Increase in PEEP resulted in a significant decrease of MAP, while V(m) MCA remained unchanged, indicating an intact cerebral autoregulation. A slight (statistically insignificant) increase in ICP, which was significantly related to the MAP changes, was evident (7 patients, 16 examinations). (3) Increase in PEEP resulted in a decrease of MAP and V(m) MCA; ICP remained unchanged or demonstrated a slight decline (3 patients, 6 examinations). CONCLUSIONS: PEEP increase up to 12 mm Hg does not significantly influence ICP. The observed marked changes in CPP are mediated through the MAP. Thus, PEEP application should be safe, provided that MAP is maintained.

Adult↗
PubMed2000

[Carotid stenosis: epidemiology and symptomatology (see comment)].

Risk factors for atherosclerotic carotid stenoses are smoking, arterial hypertension, diabetes mellitus and hypercholesterolaemia. Atherosclerotic carotid artery disease is a risk factor for the development of coronary artery disease (CAD), and in older men the risk of CAD-related death is five times higher than the risk of death related to ischaemic stroke. The prevalence of > 50% carotid stenoses in population-based studies in 6-11% for older men and 5-7% in older women. Diagnosis and differential diagnosis of ischaemia-related ophthalmologic and neurological deficits in the territory of the carotid artery are discussed.

Aged↗
PubMed2000

[Transient ischemic attacks and prolonged reversible ischemic neurologic deficit. Diagnosis, differential diagnosis and treatment].

Cerebral and ocular ischemic events are classified according to their duration and localisation in transient (< 24 hours) or permanent (> or = 24 hours) cerebral (transient ischemic attack (TIA), cerebral infarct) and ocular (amaurosis fugax, retinal infarct) deficits. The terms "Prolonged Reversible Ischemic Neurological Deficit" (PRIND, > or = 24 hours to < or = 7 days) and "Reversible Ischemic Neurological Deficit" (RIND, > or = 24 hours to < or = 3 days) are no longer used. The differential diagnosis of TIAs and ischemic strokes is discussed. Ischemic strokes are an emergency and should be referred within five hours at the latest to a centre, which offers around the clock acute therapies such as fibrinolysis and an organised stroke management. Secondary stroke prevention after TIA or stroke encompasses the treatment of vascular risk factors, carotid endarterectomy, anticoagulation in the presence of cardiac embolism (target international normalised ratio, 2.5; range 2.0-3.0) and the administration of platelet inhibitors. Carotid endarterectomy is indicated, when luminal narrowing is at least 70%, and not indicated when it is less than 50%. The benefit of endarterectomy in 50-69% stenoses decreases, and individual predictors of the operation risk are useful for choosing the appropriate treatment. Patients without indication for carotid endarterectomy or oral anticoagulation are treated with platelet inhibitors. We use the combination dipyridamole-aspirin as first choice drug, because it has been shown to be superior to aspirin and dipyridamole alone. In the presence of adverse effects or contraindications for dipyridamole we prescribe aspirin (100-300 mg daily). We administer clopidogrel (75 mg daily) if dipyridamole and aspirin are not indicated, have caused adverse effects, or did not prevent ocular or cerebral ischemic events.

Aspirin↗
PubMed2000

Comparison of the ECST, CC, and NASCET grading methods and ultrasound for assessing carotid stenosis. European Carotid Surgery Trial. North American Symptomatic Carotid Endarterectomy Trial.

We compared three angiographic methods for grading of carotid stenosis and examined the correlation between angiographic and ultrasound findings. Two observers independently measured 111 carotid stenoses on arteriographic films of 84 patients. The stenoses were graded according to the European Carotid Surgery Trial (ECST), North American Symptomatic Carotid Endarterectomy Trial (NASCET), and Common Carotid (CC) methods. The results obtained by these methods were compared, and the interobserver reproducibility of the measurements was calculated. In addition, all angiographic results were compared to ultrasound findings obtained before angiography. Measurements using the CC method were the most reproducible and those using the NASCET method the least. The NASCET method underestimated the degree of stenosis compared to the other methods. The ECST and CC methods yielded almost identical results (97% agreement). Ultrasound provided an accuracy of 94% compared to ECST and CC methods and 84% compared to the NASCET method. Interobserver reproducibility of angiographic quantification of carotid stenoses was best for the CC and ECST methods and least for the NASCET method. Ultrasound demonstrated better accuracy than the ECST and CC methods.

Adult↗
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↗