Intra- and interobsever reliability of sonographic assessment of the optic nerve sheath diameter in healthy adults

BACKGROUND

The use of an ultrasound-based evaluation of the optic nerve sheath diameter (ONSD) has previously been demonstrated for detecting raised intracranial pressure. In order to be feasible in clinical workup, the test qualities of transorbital ultrasonography need to be determined. The aim of this study was therefore to establish normal values and to assess the intra- and interobserver reliability of this method.

METHODS

Using a 9-3 MHz linear array transducer, the ONSD of 40 healthy subjects was independently measured by 2 investigators.

RESULTS

Depicting the optic nerve and its sheath was possible in all individuals. The mean ONSD was 5.4 ± .6 mm with a range of 4.3-7.6 mm. The intraobserver reliability analyzed with Cronbach's Alpha was found to be high with values between .92 and .97. Pearson's correlation coefficient between the 2 investigators was .81 on the right side and .84 on the left. There was no correlation between ONSD and age, body mass index, or gender.

CONCLUSIONS

Transorbital B-mode sonography is a feasible method to assess the ONSD with a high intra- and interobsever reliability. Normal values on ONSD are presented in this study that will be useful in future studies on pathological conditions.

Combined contrast-enhanced ultrasound and rt-PA treatment is safe and improves impaired microcirculation after reperfusion of middle cerebral artery occlusion

In monitoring of recanalization and in sonothrombolysis, contrast-enhanced ultrasound (CEUS) is applied in extended time protocols. As extended use may increase the probability of unwanted effects, careful safety evaluation is required. We investigated the safety profile and beneficial effects of CEUS in a reperfusion model. Wistar rats were subjected to filament occlusion of the right middle cerebral artery (MCA). Reperfusion was established after 90 minutes, followed by recombinant tissue-type plasminogen activator (rt-PA) treatment and randomization to additional CEUS (contrast agent: SonoVue; 60 minutes). Blinded outcome evaluation consisted of magnetic resonance imaging (MRI), neurologic assessment, and histology and, in separate experiments, quantitative 3D nano-computed tomography (CT) angiography (900 nm(3) voxel size). Nano-CT revealed severely compromised microcirculation in untreated animals after MCA reperfusion. The rt-PA partially improved hemispheric perfusion. Impairment was completely reversed in animals receiving rt-PA and CEUS. This combination was more effective than treatment with either CEUS without rt-PA or rt-PA and ultrasound or ultrasound alone. In MRI experiments, CEUS and rt-PA treatment resulted in a significantly reduced ischemic lesion volume and edema formation. No unwanted effects were detected on MRI, histology, and intracranial temperature assessment. This study shows that CEUS and rt-PA is safe in the situation of reperfusion and displays beneficial effects on the level of the microvasculature.

Effect of ApoE epsilon4 allele on visual evoked potentials and resultant flow coupling in patients with Alzheimer

The apolipoprotein E epsilon4 (ApoE epsilon4) allele is a strong susceptibility factor for Alzheimer disease, which promotes neurodegeneration and cerebrovascular dysfunction. To address this issue in more detail, we simultaneously obtained visual evoked potentials and resultant hemodynamic responses in newly diagnosed Alzheimer patients without signs of vascular lesions on a cerebral magnetic resonance imaging (MRI) scan. Patients were grouped according to ApoE genotype (n = 19 ApoE epsilon4 carrier and n = 12 noncarrier). ApoE epsilon4 carrier had significantly longer peak latencies and a trend to higher interpeak latencies of late potential components. Potential amplitudes and hemodynamic responses were similar in both groups. At the incidental stage of disease process, it appears that the ApoE epsilon4 allele mainly promotes neuronal dysfunction rather than aggravates neurovascular dysfunction. Studies with larger patient samples are warranted to corroborate the first findings.

Modeling variance structure of body shape traits of Lipizzan horses

Heterogeneity of variance of growth traits over age is a common issue in estimating genetic parameters and is addressed in this study by selecting appropriate variance structure models for additive genetic and environmental variances. Modeling and partitioning those variances connected with analyzing small data sets were demonstrated on Lipizzan horses. The following traits were analyzed: withers height, chest girth, and cannon bone circumference. The measurements were taken at birth, and at approximately 6, 12, 24, and 36 mo of age of 660 Lipizzan horses born in Croatia between 1948 and 2000. The corresponding pedigree file consisted of 1,458 horses. Sex, age of dam, and stud-year-season interaction were considered fixed effects; additive genetic and permanent environment effects were defined as random. Linear adjustments of age at measuring were done within measuring groups. Maternal effects were included only for measurements taken at birth and at 6 mo. Additive genetic variance structures were modeled by using uniform structures or structures based on polynomial random regression. Environmental variance structures were modeled by using one of the following models: unstructured, exponential, Gaussian, or combinations of identity or diagonal with structures based on polynomial random regression. The parameters were estimated by using REML. Comparison and fits of the models were assessed by using Akaike and Bayesian information criteria, and by checking graphically the adequacy of the shape of the overall (phenotypic) and component (additive genetic and environmental) variance functions. The best overall fit was obtained from models with unstructured error variance. Compared with the model with uniform additive genetic variance, models with structures based on random regression only slightly improved overall fit. Exponential and Gaussian models were generally not suitable because they do not accommodate adequately heterogeneity of variance. Using the unstructured error variance model, the heritability estimates ranged from 0.17 to 0.33 for withers height, 0.07 to 0.27 for chest girth, and 0.14 to 0.30 for cannon bone circumference. This study demonstrated the necessity of accounting for heterogeneity of variances and covariances for body shape traits in Lipizzan horses, and possible difficulties in estimating variance and covariance components when applying more complicated structure models on a small data set. The choice of models depends not only on overall fit but also on the fit of genetic and environmental components.

Active regulation of cerebral venous tone: simultaneous arterial and venous transcranial Doppler sonography during a Valsalva manoeuvre

The aim of this study was to analyse the cerebral venous outflow in relation to the arterial inflow during a Valsalva manoeuvre (VM). In 19 healthy volunteers (mean age 24.1 +/- 2.6 years), the middle cerebral artery (MCA) and the straight sinus (SRS) were insonated by transcranial Doppler sonography. Simultaneously the arterial blood pressure was recorded using a photoplethysmographic method. Two VM of 10 s length were performed per participant. Tracings of the variables were then transformed to equidistantly re-sampled data. Phases of the VM were analysed regarding the increase of the flow velocities and the latency to the peak. The typical four phases of the VM were also found in the SRS signal. The relative flow velocity (FV) increase was significantly higher in the SRS than in the MCA for all phases, particularly that of phase IV (p < 0.01). Comparison of the time latency of the VM phases of the MCA and SRS only showed a significant difference for phase I (p < 0.01). In particular, there was no significant difference for phase IV (15.8 +/- 0.29 vs. 16.0 +/- 0.28 s). Alterations in venous outflow in phase I are best explained by a cross-sectional change of the lumen of the SRS, while phases II and III are compatible with a Starling resistor. However, the significantly lager venous than the arterial overshoot in phase IV may be explained by the active regulation of the venous tone.

Ethnic Influences on Neurovascular Coupling

Background and Purpose— An ethnic extraintracranial difference in atherosclerosis has been well reported, whereas the potential mechanism remains unclear. We aimed to investigate neurovascular coupling in healthy whites and Asians.

Methods — Twenty volunteers of each ethnicity were recruited to perform a functional transcranial Doppler examination with standardized checkerboard patterns as visual stimulation (3×4, 6×8, and 12×16 checks subtending a visual field section of 18°×24°, flicker rate 1 Hz). Hemodynamic responses in both posterior cerebral arteries were evaluated with a control system approach.

Results— The rate time, that is, the initial speed of flow velocity adaptation, was significantly lower in Asians leading to an approximately 2-second delayed hemodynamic adaptation. The other hemodynamic parameters and the dependency of hemodynamic responses in regard to the complexity degree of the stimulus were similar between groups.

Conclusion— The constellation suggests a greater initial mismatch between functionally increased metabolic demand of neurons and adjusted cerebral blood flow in Asians.

Transcranial sonography for diagnosis of Parkinson's disease

Background

In idiopathic Parkinson's disease (IPD) transcranial sonography (TCS) represents an alternative diagnostic method to verify clinical diagnosis. Although the phenomenon of an increased echogenicity of the Substantia nigra (SN) is well known this method is still not widly used in the diagnostic workup. Until now reliability of this method is still a matter of debate, partly because data only existed from a few laboratories using the same ultrasound machine. Therefore our study was conducted to test the reliability of this method by using a different ultrasound device and examining a large population of control and IPD subjects by two examiners to calculate interobserver reliability.

Method

In this study echogenicity of SN was examined in 199 IPD patients and 201 control subjects. All individuals underwent a neurological assessment including Perdue pegboard test and Webster gait test. Using a Sonos 5500 ultrasound device area of SN was measured, echogenicity of raphe, red nuclei, thalamus, caudate and lenticular nuclei, width of third and lateral ventricle were documented.

Results

We found a highly characteristic enlargement of the SN echogenic signal in IPD. The cut-off value for the SN area was established using a ROC curve with a sensitivity of 95% corresponding to an area of SN of 0.2 cm² and was found to be equivalent to the cut-off values of other studies using different ultrasound devices.

Conclusions

Our study shows that TCS is a reliable and highly sensitive tool for differentiation of IPD patients from individuals without CNS disorders.

Edema formation in the hyperacute phase of ischemic stroke. Laboratory investigation

OBJECT

Brain edema formation is a serious complication of ischemic stroke and can lead to mechanical compression of adjacent brain structures, cerebral herniation, and death. Furthermore, the space-occupying effect of edema impairs regional cerebral blood flow (rCBF), which is particularly important in the penumbra phase of stroke. In the present study, the authors evaluated the natural course of edema formation in the hyperacute phase of focal cerebral ischemia.

METHODS

Middle cerebral artery occlusion (MCAO) or a sham procedure was performed in rats within an MR imaging unit (in-bore occlusion). Both pre- and postischemic images could be compared on a pixel-by-pixel basis. The T2 relaxation time (T2RT), a marker for brain water content, was measured in regions of interest.

RESULTS

A significant increase in the T2RT was detectable as early as 20-45 minutes after MCAO. At this early time point the midline shift (MLS) amounted to 0.214 +/- 0.092 cm in the MCAO group and 0.061 +/- 0.063 cm in the sham group (p < 0.007). The T2RT and MLS increased linearly thereafter. Evans blue dye was intravenously injected in additional animals 20 and 155 minutes after MCAO. Extravasation of the dye was visible in all animals, indicating increased permeability of the blood-brain barrier.

CONCLUSIONS

Vasogenic brain edema occurs much earlier than expected following permanent MCAO and leads to MLS and mechanical compression of adjacent brain structures. Since compression effects can impair rCBF, early edema formation can significantly contribute to infarct formation and thus represents a promising target for neuroprotection.

Consensus recommendations for transcranial color-coded duplex sonography for the assessment of intracranial arteries in clinical trials on acute stroke

BACKGROUND AND PURPOSE

Transcranial color-coded duplex sonography has become a standard diagnostic technique to assess the intracranial arterial status in acute stroke. It is increasingly used for the evaluation of prognosis and the success of revascularization in multicenter trials. The aim of this international consensus procedure was to develop recommendations on the methodology and documentation to be used for assessment of intracranial occlusion and for monitoring of recanalization.

METHODS

Thirty-five experts participated in the consensus process. The presented recommendations were approved during a meeting of the consensus group in October 2008 in Giessen, Germany. The project was an initiative of the German Competence Network Stroke and performed under the auspices of the Neurosonology Research Group of the World Federation of Neurology.

RESULTS

Recommendations are given on how examinations should be performed in the time-limited situation of acute stroke, including criteria to assess the quality of the acoustic bone window, the use of echo contrast agents, and the evaluation of intracranial vessel status. The important issues of the examiners' training and experience, the documentation, and analysis of study results are addressed. One central aspect was the development of standardized criteria for diagnosis of arterial occlusion. A transcranial color-coded duplex sonography recanalization score based on objective hemodynamic criteria is introduced (consensus on grading intracranial flow obstruction [COGIF] score).

CONCLUSIONS

This work presents consensus statements in an attempt to standardize the application of transcranial color-coded duplex sonography in the setting of acute stroke research, aiming to improve the reliability and reproducibility of the results of future stroke studies.

Severity of coronary artery disease but not degree of coronary stenosis is correlated to cerebrovascular reactivity

BACKGROUND

A decade difference in peak incidences of coronary and cerebral ischemia assumes a protection of the brain vasculature. Therefore, we hypothesize that early indicators of cerebrovascular disease such as parameters of the neurovascular coupling show a higher correlation to coronary artery disease than morphologic parameters.

METHODS

Stenotic degree (%) of coronary arteries (RCA, LCA, LAD, RCX) was determined together with the Gensini score by angiography in 96 patients (80 men; 62 +/- 10 years), which were grouped according to disease severity (sclerosis, 1-vessel disease (VD), 2-VD, 3-VD). Presence of internal carotid artery stenosis and left ventricular ejection fraction (LVEF) were established with duplex sonography. Resting and visually evoked hemodynamic responses were measured with transcranial Doppler ultrasound in both posterior cerebral arteries and expressed in terms of control system parameters. These were gain, natural frequency, attenuation, and rate time. Group differences and correlations between stenosis and parameters of vasoreactivity were tested.

RESULTS

Groups differed in stenotic degree of coronary arteries, Gensini score, LVEF, carotid artery stenosis, resting flow velocity, and evoked responses (gain, p < 0.005; attenuation, p < 0.05). Stenosis of each coronary artery and LVEF were correlated to carotid artery stenosis but no association was found to cerebrovascular parameters. Only severity of coronary artery disease and the Gensini score were associated with disturbed cerebrovascular reactivity. Carotid artery stenosis was associated with decreased cerebrovascular parameters (attenuation, p < 0.05; rate time, p < 0.01).

CONCLUSIONS

Although atherosclerosis is a systemic disease our data support concepts of a heterogeneous distribution of the disease indicating protection of brain vessels.

RNase therapy assessed by magnetic resonance imaging reduces cerebral edema and infarction size in acute stroke

Ischemic stroke causes cell necrosis with the exposure of extracellular ribonucleic acid (RNA) and other intracellular material. As shown recently, extracellular RNA impaired the blood-brain-barrier and contributed to vasogenic edema-formation. Application of ribonuclease 1 (RNase 1) diminished edema-formation and also reduced lesion volume in experimental stroke. Here we investigate whether reduction of lesion volume is due to the reduction of edema or of other neuroprotective means. Neuroprotective and edema protective effects of RNase 1 pretreatment were assessed using a temporary middle cerebral artery occlusion (MCAO) model in rats. Lesion volume was assessed on magnetic resonance imaging (MRI). T2-relaxation-time and midline-shift as well as brain water content (wet-dry-method) were measured to quantify edema formation. The impact of edema formation on infarct volume was evaluated in craniectomized animals. Exogenous RNase 1 was well tolerated and reduced edema-formation and infarct size (26.7% +/- 10.7% vs. 41.0% +/- 10.3%; p<0.01) at an optimal dose of 42 microg/kg as compared to placebo. Craniectomized animals displayed a comparable edema reduction but no reduction in infarct size. The present study introduces a hitherto unrecognized mechanism of ischemic brain damage and a novel neuroprotective approach towards acute stroke treatment.