摘要:

Background and PurposeDifferent frequencies of asymptomatic Doppler embolic signals have been reported in studies. There has been concern that different criteria for identification may account for some of this variation. A previous reproducibility study between two centers found good agreement, but no studies among large numbers of centers have been performed. We performed an international reproducibility study among nine centers, each of which had published recent studies of embolic signal detection in peer-reviewed journals.MethodsEach center performed blinded analysis of a taped audio Doppler signal composed of transcranial Doppler middle cerebral artery recordings from 6 patients with symptomatic carotid artery stenosis. The exact time of any embolic signal was recorded. Six centers also measured the intensity increase of any embolic signals detected. Interobserver agreement was determined by a method based on the proportion of specific agreement.Results7 dB resulted in a probability of agreement of .902. Intensity measurements made by different centers were usually highly correlated, but this was not always the case, and 3 of the 15 correlations were not significant. The absolute values of the intensities measured varied between centers by as much as 40%.ConclusionsAlthough most centers report similar numbers of embolic signals, some use less specific criteria and report more events. The use of a decibel threshold improves reproducibility. However, intensity thresholds developed by one center cannot be directly transferred without validation to another center; differing methods of measurement are being used, and this results in different intensity values for the same embolic signals, even when the same equipment is used. (Stroke. 1997;28:1307-1310.)

ISSN:0039-2499    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background and PurposeThe occurrence of microembolic signals (MES) in patients with transient ischemic attack (TIA) or stroke has already been described, but the diagnostic and prognostic value of this finding is still debated.MethodsWe evaluated 90 consecutive patients admitted for their first hemispheric TIA or ischemic stroke within 72 hours of onset. All of them underwent 30-minute bilateral transcranial Doppler monitoring of middle cerebral arteries, within 72 hours of onset. The monitoring was repeated after an additional 24 hours and after 7 days. We then classified the episodes in the following etiologic categories: cardioembolic, atherothrombotic, small-vessel disease, mixed cases, unknown origin, and other causes.ResultsWe included 75 patients, with a mean interval of registration of 32.04 +/- 19.39 hours. There were 9 patients with MES (12%). All MES were recorded only on the symptomatic middle cerebral artery, and the majority were recorded during the first or the second registration. No statistically significant difference was found in risk factors and hematologic parameters. Five patients (56%) had atherothrombotic episodes, 3 patients (33%) had cardioembolic episodes, and 1 patient (11%) had a protein S deficit. No patient with MES had small-vessel disease (P=.01).ConclusionsMES are an infrequent finding in patients with TIA or ischemic stroke within 72 hours of onset, but they can be recorded more easily with serial registration. In our patients, MES were found only on the symptomatic middle cerebral artery and were present in atherothrombotic and cardioembolic episodes but not in small-vessel disease. (Stroke. 1997;28:1310-1313.)

ISSN:0039-2499    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background and PurposeWe investigated whether cerebral microembolism as detected by transcranial Doppler ultrasonography (TCD) identifies patients at an increased risk for early, recurrent cerebral or retinal ischemic events.MethodsRecords of consecutive patients examined during a 40-month period in the Neurovascular Laboratory were reviewed for the presence of cerebral microembolism. Of the original 302 patients, 229 with 310 arteries met inclusionary criteria. Follow-up information was obtained from the laboratory's database as well as the hospital records. Microembolus detection studies were performed on TC-2000 or TC-2020 instruments equipped with special software, and criteria established a priori were used for microembolus selection. TCD testing was performed a median interval of 9 days after the initial symptoms of cerebral ischemia. Severity of arterial stenosis was determined by cerebral angiography or noninvasive methods.ResultsMicroembolic signals were detected more frequently in symptomatic (40/140; 28.6%) than asymptomatic (21/170; 12.4%) arteries (P<.001). Ten recurrent ischemic events occurred during a median follow-up of 8 days after TCD examination, all in the territories of symptomatic arteries. Nine events occurred in the territories of microembolic signal-positive arteries (9/61; 14.8%) and one in the territory of a microembolic signal-negative artery (1/249; 0.4%) (P<.001). No association was detected in the subgroup with known cardiac lesions. Microembolic signals were more frequent in arteries with lesions causing 70% or more stenosis or occlusion (26/99; 26.3%) than in those with a degree of stenosis less than 70% (17/126; 13.5%) (P=.016).ConclusionsIn this retrospective study, microembolic signals were more common in the territories of symptomatic arteries and particularly those with severely stenotic lesions. During a short follow-up, recurrent ischemic events were more common along the territories of arteries with TCD-detected microembolism and previous symptoms of cerebral or retinal ischemia. (Stroke. 1997;28:1314-1318.)

ISSN:0039-2499    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background and PurposePower-based transcranial colorcoded 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.MethodsThe 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.ResultsIn 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).ConclusionsTransoccipital 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. (Stroke. 1997;28:1319-1323.)

ISSN:0039-2499    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background and PurposeIt remains uncertain whether the annual stroke risk of 7% to 8% in middle cerebral artery (MCA) stenosis is of embolic or hemodynamic origin. Preliminary reports provide evidence of emboli exiting from acute MCA stenoses, detected by transcranial Doppler (TCD) sonography. With multirange monitoring before and after the stenosis, TCD monitoring may help for the first time to differentiate microemboli exiting from the MCA stenosis from those with a source proximal to the MCA stenosis. We searched for microembolic signals (MES) using multigated monitoring in patients with chronic MCA stenoses.MethodsFifty-eight patients with 78 chronic stenoses of the MCA were enrolled in the study. Additional sources of embolism were ruled out by extensive clinical workup. Twenty-four patients were treated with coumarin, whereas 28 patients received aspirin. The remaining 6 patients discontinued their medication after a few weeks. The sample volume of the multirange probe was placed on either side of the stenotic area of the MCA.ResultsTwenty-three (29.5%) of the stenoses were low grade, 18 (23%) were moderate, and 37 (47.5%) were severe. Thirty-seven (47%) of the stenoses were symptomatic and 41 (53%) were asymptomatic before study entry. During follow-up, 2 strokes and 7 transient ischemic attacks occurred. Computer tomography revealed two watershed-type infarcts. Sufficient insonation of the prestenotic and poststenotic segments of the MCA was possible in 70 stenoses (90%). No MES could be detected during a total of 1740 minutes' monitoring time distal to the MCA stenoses, regardless of the patients' medication. MES were also absent in the contralateral MCA.ConclusionsMES are not detectable in patients with chronic MCA stenoses of different degrees. No MES were found in either symptomatic or asymptomatic stenoses, regardless of the patients' medication. These results indicate that chronic MCA stenoses do not represent a significant embolic source. The absence of MES in the prestenotic Doppler sample volume, the watershed-type infarcts during follow-up, and the absence of small-vessel disease on computed tomography suggests that hemodynamic mechanisms are responsible for recurrent cerebral ischemia. (Stroke. 1997;28:1324-1327.)

ISSN:0039-2499    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background and PurposeThe aim of this study was the evaluation of the prevalence and counts of Doppler microembolic signals (MES) in children with prosthetic cardiac valves and their comparison to those obtained in corresponding adult patients.Patients and MethodsNine children and 43 adults with ATS valves implanted in the aortic position were monitored over both middle cerebral arteries with transcranial Doppler ultrasound. MES were identified on-line according to standard criteria. Heart rate and rhythm, valve type, size and duration, patients' height, International Normalized Ratio, and prevalence of neurological complications were obtained from all study participants.ResultsMES prevalence and counts were significantly higher in children compared with adult patients (100% versus 25.5% and 58 [18.5 to 115.5] versus 5.5 [2 to 10.5], median, 95% CI, respectively). No corresponding differences in valve size or duration of valve implant were evident, but children had faster heart rates and were significantly smaller compared with adults. A positive correlation between patients' size, heart rate, and MES counts was noted.ConclusionsMES counts in children with mechanical prosthetic valves are significantly higher compared with those in corresponding adults. We hypothesize that this is due to (1) the shorter distance between aortic valve and middle cerebral artery, since cavitation bubbles have a short life span and are bound to dissolve with time, and (2) the faster heart rate in children, resulting in a higher number of valve closures per minute. (Stroke. 1997;28:1328-1329.)

ISSN:0039-2499    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background and PurposeSeveral recent clinical trials have shown that endarterectomy is efficacious in patients with asymptomatic carotid artery stenosis. The purpose of this study was to evaluate the effectiveness of various test strategies for screening and diagnosing carotid artery disease.MethodsWe constructed a model of the natural history of carotid artery disease using literature-based estimates of the prevalence and incidence of carotid artery stenosis and associated morbidity and mortality. Markov cohort simulation was used to estimate the mean quality-adjusted life years and monetary costs associated with various management strategies.ResultsScreening is cost-effective in the baseline model. Key parameters affecting the efficacy of screening are prevalence of operable lesions, benefit of surgery, surgical complication rates, quality of life with stroke, rate of stenosis progression, and excess morbidity and mortality.Conclusionsor=to20%, the benefits and risks associated with surgery are similar to those observed in the Asymptomatic Carotid Atherosclerosis Study, and the quality of life with stroke is considerably lower than the quality of life without stroke. Ultrasound followed by three-dimensional time-of-flight MR angiography, if indicated, is a promising test strategy. (Stroke. 1997;28:1330-1339.)

ISSN:0039-2499    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background and PurposeIf it could be determined whether cerebral blood flow can be maintained (autoregulated) during transient falls in arterial blood pressure, we might be able to identify patients with carotid stenosis who are at risk of stroke. However, conventional methods of determining autoregulation in such patients are invasive and/or expensive.MethodsWe used a new noninvasive method to estimate dynamic cerebral autoregulation in 27 patients with carotid stenosis and 21 age-matched normal controls. After a stepwise fall in arterial blood pressure, we determined the rate of rise of middle cerebral artery blood flow velocity compared with that of arterial blood pressure. We compared the method with a conventional method of determining cerebral hemodynamics, CO2reactivity.ResultsAutoregulatory index (ARI) was significantly reduced in middle cerebral arteries ipsilateral to a stenosed/occluded carotid artery: mean +/- SD 3.3 +/- 2.2 compared with normal controls (6.3 +/- 1.1; P<.0001) and nonstenosed carotid arteries in patients (5.9 +/- 2.1; P<.002). A subgroup of patients with severe impairment was identified. ARI returned to normal after carotid endarterectomy was performed. In a number of cases, ARI was impaired in the presence of CO2reactivity.ConclusionsThis simple technique allows identification of impaired autoregulation in patients with carotid artery disease. It may allow identification of patients at risk from transient falls of blood pressure as may occur at the onset of antihypertensive therapy and during surgery. It may allow a subgroup of patients with asymptomatic carotid stenosis who are at risk of hemodynamic stroke to be identified. (Stroke. 1997;28:1340-1344.)

ISSN:0039-2499    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background and PurposeIntraoperative monitoring of brain function may influence the outcome of carotid endarterectomy (CEA).MethodsWe performed transcranial Doppler (TCD) monitoring of middle cerebral artery blood flow velocities (VMCAs) and eight-channel electroencephalographic (EEG) recording simultaneously in 82 patients undergoing CEA. Thiopental narcosis limited EEG interpretation in 11 patients, thus allowing direct comparison of both methods in 71 patients.ResultsThere was a significant correlation between VMCA decrease and the frequency of EEG changes after carotid clamping (P<.001). Eight patients (11%) showed a VMCA decrease exceeding 60%, accompanied by EEG changes in 7 patients. Altogether, 16 patients (22%) showed severe or moderate EEG changes. Stenosis or occlusion of the contralateral carotid artery led to an increase of abnormal findings with both monitoring methods, which was, however, significant only for TCD (P<.05). Four patients (4.8%) suffered intraoperative transient ischemic attacks. In 3 of these patients, there were no abnormal findings with either of the methods. The events were thus unpredictable and probably of embolic origin. The fourth patient showed VMCA decrease to 0 and severe EEG changes. Nine patients had severe or moderate EEG changes without significant VMCA decrease and without complications. EEG monitoring alone in these would have led to unnecessary use of a shunt with the increased risk of embolism.ConclusionEEG and TCD monitoring are complementary techniques. Their results showed a good overall correlation but with marked differences in the individual patient. TCD monitoring alone was sensitive enough to prevent ischemic intraoperative complications. EEG findings are of limited value when barbiturates are used. (Stroke. 1997;28:1345-1350.)

ISSN:0039-2499    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background and PurposeA number of clinical observations and first in vitro findings indicate that chronic cerebral ischemia influences immunologic status, such as the proliferative response of T lymphocytes. The purpose of the present report was to assess (1) whether changes of immune function are likewise detectable in patients with progressive subcortical vascular encephalopathy (SVE) by investigating the [Ca sup 2+]ihomeostasis of lymphocytes and (2) whether differences exist in calcium regulation between lymphocytes from SVE patients and from Alzheimer's disease (AD) patients. This is of great interest, since specific changes have been reported recently in AD patients.Methods[Ca2+]iwas recorded in 26 patients with SVE, 26 age-matched nondemented control subjects, and 26 age-matched patients with AD. Basal [Ca2+]iand [Ca2+]iafter lymphocyte activation with the mitogen phytohemagglutinin (PHA) were measured with the fura 2 method. In addition, modulation of the Ca2+ signaling by the peptide beta-amyloid and the potassium channel blocker tetraethylammonium was studied.ResultsBasal [Ca2+]iwas not different between patients and control subjects. After stimulation with PHA, however, a significant reduction of the Ca sup 2+ response could be observed in lymphocytes of SVE patients compared with control subjects and with AD patients, providing evidence that the Ca2+ homeostasis of lymphocytes is impaired in SVE. The effect of the peptide beta-amyloid, the major constituent of senile plaques in AD brain, on Ca2+ signaling was similar in SVE patients and nondemented control subjects but typically reduced in cells of AD patients. Potassium channels were not involved in the impaired Ca2+ response of SVE lymphocytes after cell activation.Conclusions[Ca2+]iis not only one of the most important second messengers in signal transduction of many cells but also an early event in the signal cascade of cell proliferation as a reaction to antigen recognition. This mechanism seems to be impaired in SVE. These findings may result in new insights regarding the pathogenesis of this disease and the possible involvement of inflammatory or immunologic disturbances.(Stroke. 1997;28:1351-1356.)

ISSN:0039-2499    

出版商:OVID    

年代:1997

数据来源: OVID