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Biomedical subjects

Ralf W Baumgartner

Publications and source records attributed to Ralf W Baumgartner.

At least 19 recordsLinked to original sources
PubMed2006

Spontaneous and endothelial-independent vasodilation are impaired in patients with spontaneous carotid dissection: a case-control study.

BACKGROUND AND PURPOSE: We undertook this case-control study in patients with unilateral spontaneous dissection of the cervical internal carotid artery to investigate spontaneous and endothelium-independent dilation of the nondissected, contralateral carotid arteries and the ipsilateral brachial artery using high-resolution ultrasound. METHODS: Spontaneous and endothelial-independent (nitroglycerin-mediated) absolute and relative dilation were assessed in the internal and common carotid and brachial arteries of 27 patients with unilateral spontaneous dissection of the cervical internal carotid artery and 27 age- and sex-matched healthy controls. RESULTS: Absolute and relative spontaneous and endothelial-independent dilation of the carotid, but not brachial arteries, were significantly lower in patients as compared with controls. CONCLUSIONS: Vasodilation abnormalities may be a predisposing factor for spontaneous dissection of the cervical internal carotid artery.

Adult↗
PubMed2006

Vertebral artery dissection: presenting findings and predictors of outcome.

BACKGROUND AND PURPOSE: Few data exist about clinical, radiologic findings, clinical outcome, and its predictors in patients with spontaneous vertebral artery dissection (sVAD). METHODS: Clinical characteristics, imaging findings, 3-month outcomes, and its predictors were investigated in consecutive patients with sVAD. RESULTS: One hundred sixty-nine patients with 195 sVAD were identified. Brain ischemia occurred in 131 patients (77%; ischemic stroke, n=114, 67%; transient ischemic attack, n=17, 10%). Three patients with ischemic stroke showed also signs of subarachnoid hemorrhage (SAH); 3 (2%) had SAH without ischemia. The 134 patients with brain ischemia or SAH had head and/or neck pain in 118 (88%) and pulsatile tinnitus in seven (5%) patients. The remaining 35 patients (21%) had isolated head and/or neck pain in 21 (12%) cases, asymptomatic sVAD in 13 (8%), and cervical radiculopathy in one case (1%). Location of sVAD was more often in the pars transversaria (V2; 35%) or atlas loop (V3; 34%) than in the prevertebral (V1; 20%) or intracranial (V4; 11%) segment (P=0.0001). Outcome was favorable (modified Rankin scale score 0 or 1) in 88 (82%) of 107 ischemic stroke patients with follow up. Two (2%) patients died. Low baseline National Institutes of Health Stroke Scale score (P<0.0001) and younger age (P=0.007) were independent predictors of favorable outcome. CONCLUSIONS: sVAD is predominantly located in the pars transversaria (V2) or the atlas loop (V3). Most patients show posterior circulation ischemia. Favorable outcome is observed in most ischemic strokes and independently predicted by low National Institutes of Health Stroke Scale score and younger age.

Brain Ischemia↗
PubMed2006

Good outcomes in ischemic stroke patients treated with intravenous thrombolysis despite regressing neurological symptoms.

BACKGROUND AND PURPOSE: We evaluated the clinical course of 19 acute stroke patients with rapid early improvement of neurological deficit within the 3-hour window, treated with intravenous thrombolytics. RESULTS: No patient demonstrated a neurological deterioration during hospitalization. National Institutes of Health Stroke Scale (NIHSS) scores at therapy decision and discharge were 5 (4 to 6) and 0.5 (0 to 1.5), respectively. At 3-month follow-up, 1 patient had died; in remaining patients, NIHSS was 0 (0 to 1) and modified Rankin Scale 0.5 (0 to 1; < or =1 in 15 patients). CONCLUSIONS: Withholding of intravenous thrombolysis because of spontaneous early regression of neurological symptoms may not be justified.

Adult↗
PubMed2006

Sirolimus-eluting stenting of the external carotid artery for the treatment of ocular ischemia.

PURPOSE: To present a patient in whom severe external carotid artery (ECA) stenosis causing ocular ischemia was treated with a drug-eluting stent. CASE REPORT: A 55-year-old woman with severe, diffuse atherosclerosis presented with impaired left ocular perfusion and amaurosis fugax. Duplex ultrasonography and angiography documented bilateral occlusion at the origin of the internal carotid arteries, bilateral subtotal ECA stenoses, and subtotal distal left common carotid artery (CCA) restenosis following endarterectomy. Percutaneous revascularization of the left ECA and CCA stenoses was performed using a short coronary balloon-expandable sirolimus-eluting stent and a self-expanding nitinol stent, respectively. The procedure was uneventful, and the ocular symptoms resolved. At 6 months, the patient remained asymptomatic, with angiographically patent stents. CONCLUSION: Drug-eluting stenting may be a novel option to treat symptomatic ECA stenosis.

Alloys↗
PubMed2005

Accuracy of color duplex ultrasound diagnosis of spontaneous carotid dissection causing ischemia.

BACKGROUND AND PURPOSE: Spontaneous dissection of the cervical internal carotid artery (sICAD) is mainly assessed with MRI and magnetic resonance angiography (MRA), which are not always at hand. In contrast, color duplex sonography (CDS) is readily available. We undertook this prospective study to examine the accuracy of CDS to diagnose sICAD in patients with first carotid territory ischemia. METHODS: Consecutive patients with first carotid territory stroke or transient ischemic attack or retinal ischemia underwent clinical and laboratory examinations, ECG, CDS of the cerebral arteries, cranial computed tomography in case of stroke or transient ischemic attack, and echocardiography and 24-hour ECG in selected cases. Patients were included, if they were <65 years of age, CDS showed a probable sICAD (cervical internal carotid artery stenosed or occluded), or had no determined etiology of ischemia. All of the included patients underwent cervical MRI and MRA+/-cerebral catheter angiography. The sonographer was blinded to the results of MRI and angiography studies. RESULTS: We included 177 of 1652 screened patients. Excluded patients (n=1475) were > or =65 years old (n=818), had another determined cause of ischemia (n=1475), and had intracranial hemorrhage (n=58). CDS diagnosed sICAD in 77 of 177 patients, and the etiology of ischemia was undetermined in the remaining 100 patients. Cervical MRI and angiography showed 74 sICAD; there were 6 falsely positive and 3 falsely negative CDS findings. Thus, sensitivity, specificity, and positive and negative predictive values for CDS diagnosis of patients with sICAD causing carotid territory ischemia was 96%, 94%, 92%, and 97%, respectively. CONCLUSIONS: Color duplex ultrasound allows the reliable exclusion of sICAD in patients with carotid territory ischemia, whereas diagnosis of CDS of sICAD must be confirmed with cervical MRI and MRA.

Aged↗
PubMed2005

Lateralization of cerebral hemodynamics during Wisconsin Card Sorting Test: a functional transcranial Doppler sonography study.

OBJECTIVE: Studies on lateralization of cerebral metabolism during Wisconsin Card Sorting Test (WCST), a well-known paradigm of category learning, have shown mixed results. Moreover, sorting dimension (number, color and shape) is a cofounder of laterality in WCST. Functional transcranial Doppler sonography (fTCD) has a high temporal resolution and allows the measurement of mean cerebral blood flow velocity (CBFV) in the middle (MCA) and anterior cerebral arteries (ACA), which supply lateral and medial parts of the frontal and parietal lobes, respectively. We used fTCD to investigate CBFV changes occurring in both MCA and ACA during WCST and different sorting dimensions. METHODS: Twenty-one subjects underwent twice two distinct phases of the WCST, namely maintaining a rule (maintaining set) and searching for a new rule (set shifting), during bilateral fTCD of the MCA and ACA. RESULTS: There was a left-sided dominance of CBFV during maintaining set and set shifting in the MCA. CBFV was not associated with test performance. The sorting dimension number caused the highest CBFV increase in both MCA and ACA during maintaining set, and the sorting dimension shape caused lowest CBFV decrease in both MCA during set shifting. CONCLUSIONS: This study confirms results that cerebral blood flow (CBF) lateralizes to the left side during WCST. The 3 sorting dimensions provoked distinct processing speed during maintaining set and set shifting, but caused no effect on hemispheric lateralization. SIGNIFICANCE: Functional transcranial Doppler sonography can be used to assess CBFV during WCST and different sorting dimensions, and the latter modulate reaction time and cerebral hemodynamics.

Adult↗
PubMed2004

Cerebral hemodynamics and processing speed during category learning.

The Wisconsin Card Sorting Test (WCST) is a commonly used paradigm of category learning with two alternating and distinct processes, maintaining set and set shifting that have been characterized by functional transcranial Doppler sonography (fTCD) of the basal cerebral arteries. Further, repeated WCST administrations resulted in improved speed of solution. This study addressed the question of whether optimised speed during maintaining set or set shifting is associated with changes of cerebral hemodynamics as measured by bilateral fTCD. During maintaining set, improved speed was associated with increased peak mean cerebral blood flow velocity (CBFV) of the anterior cerebral arteries. These results suggest a common functional substrate between optimised speed of solution and cerebral hemodynamics during maintaining set.

Adult↗
PubMed2004

Acute mountain sickness: controversies and advances.

This review discusses the impact of recent publications on pathophysiologic concepts and on practical aspects of acute mountain sickness (AMS). Magnetic resonance imaging studies do not provide evidence of total brain volume increase nor edema within the first 6 to 10 h of exposure to hypoxia despite symptoms of AMS. After 16 to 32 h at about 4500 m, brain volume increases by 0.8% to 2.7%, but morphological changes do not clearly correlate with symptoms of AMS, and lumbar cerebrospinal fluid pressure was unchanged from normoxic values in individuals with AMS. These data do not support the prevailing hypothesis that AMS is caused by cerebral edema and increased intracranial pressure. Direct measurement of increased oxygen radicals in hypoxia and a first study reducing AMS when lowering oxygen radicals by antioxidants suggest that oxidative stress is involved in the pathophysiology of AMS. Placebo-controlled trials demonstrate that theophylline significantly attenuates periodic breathing without improving arterial oxygen saturation during sleep. Its effects on AMS are marginal and clearly inferior to acetazolamide. A most recent large trial with Ginkgo biloba clearly showed that this drug does not prevent AMS in a low-risk setting in which acetazolamide in a low dose of 2 x 125 mg was effective. Therefore, acetazolamide remains the drug of choice for prevention and the recommended dose remains 2 x 250 mg daily until a lower dose has been tested in a high-risk setting and larger clinical trials with antioxidants have been performed.

Acetazolamide↗
PubMed2004

Clinical applications of transcranial color-coded duplex sonography.

Transcranial color-coded duplex sonography (TCCS), in contrast to "blind" conventional transcranial Doppler sonography (TCD), enables a sonographer to outline the intracranial bony and parenchymal structures, visualize the basal cerebral arteries in color, and measure angle-corrected blood flow velocities in a specific site of the artery in question. This makes measurements of flow velocity more valid than those obtained with conventional TCD. TCCS is becoming a reliable tool for detecting the occlusion and narrowing of major intracranial arterial trunks. TCCS can image the collateral flow through the anterior and posterior communicating arteries in patients with unilateral, high-grade stenosis or occlusion of the extracranial internal carotid artery, without using potentially dangerous compression tests. Large and medium-sized arteriovenous malformations can also be detected with TCCS. The rapid sonographic assessment of cerebral hemodynamics in a neurosurgical patient with increased intracranial pressure can guide further management. The use of sonographic contrast agents can increase the number of conclusive TCCS studies in patients with insufficient acoustic windows.

Blood Flow Velocity↗
PubMed2004

Progressive occlusive disease of large cerebral arteries and ischemic events in a patient with essential thrombocythemia.

We report a patient with essential thrombocythemia (ET) who developed progressive occlusive cerebrovascular disease accompanied by ischemic events. A 40-year-old woman presented with an ischemic stroke in the territory of the left middle cerebral artery (MCA). Diagnostic work-up disclosed a moderate stenosis of the left carotid siphon and a mildly increased platelet count. Due to aspirin intolerance warfarin was administered. Twelve months later, ischemic strokes in the left MCA territory recurred. A left internal carotid artery occlusion at the origin was diagnosed. Bone marrow biopsy showed an increased number of megakaryocytes. Warfarin was replaced by clopidogrel. Cerebral artery obstructions remained unchanged during the next 3 years (six follow-up examinations); no further ischemic events occurred during that period, while mild thrombocytosis persisted. ET may be associated with progressive obstructions of large cerebral arteries; in our case, clopidogrel was effective in preventing recurrence of ischemic events.

Adult↗
PubMed2004

Doppler microembolic signals during cardiopulmonary bypass: comparison of two membrane oxygenators.

We undertook this study to evaluate the dependence of Doppler microembolic signal (MES) counts, detected during cardiopulmonary bypass, on the type of oxygenator used. A total of 90 patients, 71 men and 19 women, aged 60 +/- 10 years (mean +/- SD), undergoing elective cardiac surgery for coronary artery bypass grafting (one vessel, n = 6; two vessels, n = 24; three vessels, n = 33; four vessels, n = 9) or valve replacement (mitral valve, n = 2, aortic valve, n = 15, both valves, n = 1) were monitored with transcranial Doppler sonography during the complete surgical procedure. The surgical and anesthetic techniques were standardized in all patients, except for the type of membrane oxygenator used (COBE CML Duo, n = 55 or DIDECO D 703, n = 35). MES count was expressed as total number of MES detected in both middle cerebral arteries during cardiopulmonary bypass (CPB) and also as total MES number divided by the CPB duration in minutes (MES min(-1)). No significant differences in patients' age or sex and type and duration of operation were noted between the two groups. MES incidence while the patients were on cardiopulmonary bypass was 100%. MES counts during CPB were 309 (236-502) and 143 (86-233) for DIDECO and COBE oxygenators, respectively (p < 0.00001). MES min(-1) were also significantly higher in patients operated with DIDECO, as compared to COBE oxygenators (3.7 (2.4-5.6) versus 1.5 (1-2.4), respectively, p < 0.0001). Inter-observer variability was satisfactory (k = 0.72). Use of a DIDECO D 703 oxygenator resulted in significantly higher MES counts as compared to the COBE CML Duo oxygenator. The clinical relevance of this finding remains to be determined.

Age Factors↗
PubMed2003

Ischemic lacunar stroke in patients with and without potential mechanism other than small-artery disease.

BACKGROUND AND PURPOSE: Autopsy studies found that lacunar strokes differ in the size of the underlying brain infarct and that small lacunes are usually caused by hypertensive small-artery disease (SAD) and larger ones by atheromatous or embolic perforator occlusion. These findings suggest that larger lacunar infarcts might cause more severe neurological deficits and a higher detection rate on brain imaging compared with lacunar strokes caused by SAD. This prospective observational study was performed to investigate whether (1) neurological outcome, (2) prevalence of stroke risk factors, (3) prevalence of clinically asymptomatic occlusive cerebral artery disease, and (4) detection rate of underlying lacunar infarcts at brain imaging differ in ischemic lacunar strokes with (non-SAD) and without potential etiologies other than SAD. METHODS: Consecutive patients with lacunar stroke (n=244), defined by both clinical findings and brain imaging, were studied. Neurological deficit was quantified at presentation with the use of the National Institutes of Health Stroke Scale (NIHSS) and after 3 months with the NIHSS and the modified Rankin Scale (mRS). Cerebral arteries were investigated by ultrasound. RESULTS: Compared with patients with SAD lacunar strokes (n=155; 64%), patients with non-SAD lacunar strokes (n=89; 36%) had (1) higher NIHSS scores at presentation and higher NIHSS and mRS scores after 3 months (P<0.05); a higher prevalence of (2) hypertension (P<0.05), (3) coronary artery disease (P<0.0001), (4) previous transient ischemic attacks (P<0.01), and (5) asymptomatic stenoses of intracranial cerebral (P<0.01 to P<0.0001) and extracranial carotid (30% to 50% narrowing; P<0.01) arteries; and (6) a higher detection rate of the underlying lesion at brain imaging (P<0.01). CONCLUSIONS: Our data suggest that patients with non-SAD lacunar strokes have a worse clinical outcome and a higher prevalence of large cerebral and coronary artery disease than patients with SAD lacunar strokes.

Adolescent↗
PubMed2003

Flunarizine in prevention of headache, ataxia, and memory deficits during decompression to 4559 m.

Our purpose was to study the preventive effect of the calcium channel blocker flunarizine on headache, postural ataxia, and memory deficits occurring during decompression to high altitude in a randomized, placebo-controlled, double-blind study. After 7-day pretreatment with the study drugs, 20 healthy men were investigated at 490 m and 0.5, 2, 4, and 6 h later at a simulated altitude of 4559 m. Headache severity was evaluated on a 4-point scale. Sway path and anteroposterior and lateral sway were recorded with open and closed eyes by static posturography. Short- and long-term memory was studied by testing the recall of verbal and figural material immediately and 2 h after presentation, respectively. Blood pressure (BP) and arterial oxygen saturation (Sa(O2)) were also assessed. Headache scores showed a trend to be lower in the flunarizine group that was significant after 4 and 6 h. Headache scores expressed as difference from baseline values showed a nonsignificant trend to be lower at 4 and 6 h in subjects treated with flunarizine. Postural stance, memory, BP, and Sa(O2) were similar in both treatment groups. Although the low number of investigated subjects may have prevented the detection of a significant therapeutic effect of flunarizine, the present data do not show that flunarizine is effective for prevention of headache, postural ataxia, and neurocognitive deficits occurring at simulated high altitude.

Adult↗
PubMed2003

Transcranial color duplex sonography in cerebrovascular disease: a systematic review.

Transcranial color-coded duplex sonography (TCCS) enables the reliable assessment of intracranial stenoses (sensitivity 94-100%, specificity 99-100%), occlusions (middle cerebral artery: sensitivity 93-100%, specificity 98-100%) and cross-flow through the anterior (sensitivity 98%, specificity 100%) and posterior (sensitivity 84%, specificity 94%) communicating arteries without using potentially dangerous compression tests, as well as the midline shift in hemispheric infarcts. Ultrasound contrast agents (UCAs) increase the number of conclusive TCCS studies and allow the definite evaluation of intracranial arteries in most patients. TCCS is also useful for diagnosis and monitoring of vasospasm and detection of supratentorial hematomas (sensitivity 94%, specificity 95%) and aneurysms (sensitivity per patient 40-78%, specificity 90-91%), and may identify arteriovenous malformations. New developments are (1) UCAs that may increase the number of conclusive TCCS studies, (2) cerebral perfusion assessment, (3) measurement of arteriovenous cerebral transit time, which might enable the detection of small-vessel disease, and (4) site-targeted UCAs that may improve diagnosis and local drug delivery.

Cerebrovascular Disorders↗
PubMed2003

Postembolic spectral patterns of Doppler microembolic signals.

OBJECTIVES: This study was performed to examine the prevalence of postembolic spectral patterns in patients with prosthetic heart valves and evaluate their potential relation to the underlying embolic material. METHODS: The prevalence of the tail (TS) and lambda (LS) signs was examined in artifact signals and microembolic signals (MES) detected in 10 patients with prosthetic heart valves and 13 further patients with artificial heart valves during normobaria as well as during hyperbaric exposure (2.5 and 1.75 bar). RESULTS: A total of 1,721 MES were detected in the 10 patients; prevalence of TS and LS were 11 and 9.8%, respectively. Hyperbaric exposure in the second group of patients resulted in a significant increase of the prevalence of LS (13.7% at 2.5 bar and 9.2% at 1.75 bar, as compared to 7.7 and 8.2% during normobaria), while the prevalence of TS remained unchanged, ranging between 5 and 6.7%. Neither TS nor LS was observed following artifact signals. CONCLUSIONS: TS and LS showed a high specificity (100%) but low sensitivity (ranging between 7.7 and 11 and 5 and 9.8%, respectively) for the detection of MES. LS appear to be--at least partially--associated with gaseous embolic material.

Adult↗
PubMed2002

Influence of inspiration:expiration ratio on intracranial and cerebral perfusion pressure in acute stroke patients.

OBJECTIVE: We undertook this study to evaluate the influence of the inspiration:expiration (I:E) ratio on intracranial pressure and cerebral perfusion in patients with acute stroke. DESIGN: Ventilated patients with acute stroke were examined under a protocol involving variations of I:E ratio from 1:2 to 1:1 to 1:2 under positive end-expiratory pressure (PEEP) of 5.3 and - subsequently - 10.6 cmH(2)O. Intracranial pressure was monitored with parenchymal or ventricular catheters. Mean arterial blood pressure, intracranial pressure (ICP), heart rate and peak mean flow velocity of the middle cerebral arteries were continuously recorded. SETTING: Neurological intensive care unit. PATIENTS: A total of 45 monitoring sessions were performed in 16 patients (subarachnoid haemorrhage 3, ischemic stroke 13). RESULTS: No significant changes in any of the parameters monitored were evident in association with the I:E ratio variations under either of the PEEP levels applied. It must be noted, though, that ICP exceeded 15 mmHg in only 5/45 monitoring sessions, and never exceeded 20 mmHg. CONCLUSIONS: Our preliminary results suggest that variations of the I:E ratio cause no significant changes in intracranial or cerebral perfusion pressure and, thus, can be safely used in patients with acute stroke without intracranial hypertension. The influence of I:E ratio variations on stroke patients with intracranial hypertension remains to be evaluated.

Adult↗