18F-Sodium fluoride positron emission tomography, aortic disease activity and ischaemic stroke risk

Background

Arterial 18F-sodium fluoride (18F-NaF) activity on positron emission tomography (PET) is a marker of active microcalcification and atherosclerosis. Coronary 18F-NaF activity (CMA) predicts coronary artery disease progression and subsequent myocardial infarction.

Objective

To investigate whether aortic 18F-NaF activity (AMA) predicts thoracic aortic atherosclerotic disease progression and subsequent ischaemic stroke or myocardial infarction in patients with established cardiovascular disease.

Methods

In a post-hoc observational cohort study, we evaluated AMA and CMA in patients with stable coronary artery disease (n=239) or aortic stenosis (n=158) who had underwent thoracic 18F-NaF PET and computed tomography (CT). We assessed the associations between AMA or CMA and progression of calcified atherosclerotic plaque in both thoracic aortic and coronary territories on follow up CT, as well as subsequent ischaemic stroke or myocardial infarction.

Results

In 141 and 231 patients with repeat aortic and coronary CT imaging respectively at 12.7±2.7 months, AMA correlated with log progression of thoracic aortic calcium scores (r=0.21, p=0.011), volume (r=0.29, p<0.01) and mass (r=0.29, P<0.01) as well as log coronary calcium score progression (r=0.21, p=0.03). CMA correlated with log coronary (r=0.42, p<0.01), but not log aortic (p>0.80) calcium score progression. In 397 patients, 16 had an ischaemic stroke and 25 had a myocardial infarction after 4.7±1.6 years. After adjusting for clinical risk factors, CMA and calcium scoring, AMA was associated with stroke (hazard ratio, 1.71 [95% confidence interval 1.00–2.90], p=0.048]). AMA was superior to clinical risk and calcium scores in identifying patients with stroke (c-statistic 0.76 versus 0.58 versus 0.63 respectively, p<0.05). Survival analysis demonstrated that AMA was associated with ischaemic stroke (p<0.001) but not myocardial infarction (p=0.45), whereas CMA was associated with myocardial infarction (p<0.001) but not stroke (p=0.39).

Conclusions

In patients with established cardiovascular disease, AMA is associated with progression of aortic atherosclerosis and future ischaemic stroke. Arterial 18F-NaF identifies localised areas of atherosclerotic disease activity that relate to regional atherothrombotic events.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): British Heart Foundation AMA, disease progression and outcomesVariables associated with stroke

Roadmap Consensus on Carotid Artery Plaque Imaging and Impact on Therapy Strategies and Guidelines: An International, Multispecialty, Expert Review and Position Statement

Current guidelines for primary and secondary prevention of stroke in patients with carotid atherosclerosis are based on the quantification of the degree of stenosis and symptom status. Recent publications have demonstrated that plaque morphology and composition, independent of the degree of stenosis, are important in the risk stratification of carotid atherosclerotic disease. This finding raises the question as to whether current guidelines are adequate or if they should be updated with new evidence, including imaging for plaque phenotyping, risk stratification, and clinical decision-making in addition to the degree of stenosis. To further this discussion, this roadmap consensus article defines the limits of luminal imaging and highlights the current evidence supporting the role of plaque imaging. Furthermore, we identify gaps in current knowledge and suggest steps to generate high-quality evidence, to add relevant information to guidelines currently based on the quantification of stenosis.

White matter hyperintensity and stroke lesion segmentation and differentiation using convolutional neural networks

White matter hyperintensities (WMH) are a feature of sporadic small vessel disease also frequently observed in magnetic resonance images (MRI) of healthy elderly subjects. The accurate assessment of WMH burden is of crucial importance for epidemiological studies to determine association between WMHs, cognitive and clinical data; their causes, and the effects of new treatments in randomized trials. The manual delineation of WMHs is a very tedious, costly and time consuming process, that needs to be carried out by an expert annotator (e.g. a trained image analyst or radiologist). The problem of WMH delineation is further complicated by the fact that other pathological features (i.e. stroke lesions) often also appear as hyperintense regions. Recently, several automated methods aiming to tackle the challenges of WMH segmentation have been proposed. Most of these methods have been specifically developed to segment WMH in MRI but cannot differentiate between WMHs and strokes. Other methods, capable of distinguishing between different pathologies in brain MRI, are not designed with simultaneous WMH and stroke segmentation in mind. Therefore, a task specific, reliable, fully automated method that can segment and differentiate between these two pathological manifestations on MRI has not yet been fully identified. In this work we propose to use a convolutional neural network (CNN) that is able to segment hyperintensities and differentiate between WMHs and stroke lesions. Specifically, we aim to distinguish between WMH pathologies from those caused by stroke lesions due to either cortical, large or small subcortical infarcts. The proposed fully convolutional CNN architecture, called uResNet, that comprised an analysis path, that gradually learns low and high level features, followed by a synthesis path, that gradually combines and up-samples the low and high level features into a class likelihood semantic segmentation. Quantitatively, the proposed CNN architecture is shown to outperform other well established and state-of-the-art algorithms in terms of overlap with manual expert annotations. Clinically, the extracted WMH volumes were found to correlate better with the Fazekas visual rating score than competing methods or the expert-annotated volumes. Additionally, a comparison of the associations found between clinical risk-factors and the WMH volumes generated by the proposed method, was found to be in line with the associations found with the expert-annotated volumes.

•

Robust, fully automatic white matter hyperintensity and stroke lesion segmentation and differentiation

•

A novel patch sampling strategy used during CNN training that avoids the introduction of erroneous locality assumptions

•

Improved segmentation accuracy in terms of Dice scores when compared to well established state-of-the-art methods

Cytomegalovirus infection is associated with an increase in systolic blood pressure in older individuals

BACKGROUND

Cytomegalovirus (CMV) is a chronic infection that is widely distributed in the population. CMV infects a range of tissues, including endothelium, and viral replication is suppressed by the host immune system. Infection is associated with increased risk of mortality from vascular disease in older people, but the mechanisms behind this have not been determined.

AIM

We investigated the association between CMV infection and cardiovascular phenotype in a cohort of healthy elderly donors.

DESIGN

CMV serostatus and cardiovascular parameters were determined in the Lothian Birth cohort, which comprises 1091 individuals aged 70 years in whom many environmental, biochemical and radiological correlates of vascular function have been determined.

METHODS

CMV serostatus was determined by enzyme-linked immunosorbant assay and correlated with a range of biochemical and phenotypic measures.

RESULTS

Sixty-five percent of participants were CMV seropositive, which indicates chronic infection. The mean sitting systolic blood pressure (SBP) was 149.2 mmHg in CMV seropositive individuals compared with 146.2 mmHg in CMV seronegative subjects (SD 18.7 vs. 19.7; P < 0.017). This association between CMV infection and SBP was not attenuated after adjustment for a wide range of biological and socio-economic factors.

CONCLUSIONS

These data show that CMV infection is associated with an increase in SBP in individuals at age 70 years. The magnitude is comparable to environmental variables such as obesity, diabetes or high salt intake. This is the first evidence to show that a chronic infection may be an important determinant of blood pressure and could have significant implications for the future management of hypertension.

Do white matter hyperintensities mediate the association between brain iron deposition and cognitive abilities in older people?

BACKGROUND AND PURPOSE

Several studies have reported associations between brain iron deposits (IDs), white matter hyperintensities (WMHs) and cognitive ability in older individuals. Whether the association between brain IDs and cognitive abilities in older people is mediated by or independent of total brain tissue damage represented by WMHs visible on structural magnetic resonance imaging (MRI) was examined.

METHODS

Data from 676 community-dwelling individuals from the Lothian Birth Cohort 1936, with Mini-Mental State Examination scores >24, who underwent detailed cognitive testing and multimodal brain MRI at mean age 72.7 years were analysed. Brain IDs were assessed automatically following manual editing. WMHs were assessed semi-automatically. Brain microbleeds were visually counted. Structural equation modelling was used to test for mediation.

RESULTS

Overall, 72.8% of the sample had IDs with a median total volume of 0.040 ml (i.e. 0.004% of the total brain volume). The total volume of IDs, significantly and negatively associated with general cognitive function (standardized β = -0.17, P < 0.01), was significantly and positively associated with WMH volume (std β = 0.13, P = 0.03). WMH volume had a significant negative association with general cognitive function, independent of IDs (std β = -0.13, P < 0.01). The association between cognition and IDs in the brain stem (and minimally the total brain iron load) was partially and significantly mediated by WMH volume (P = 0.03).

CONCLUSIONS

The negative association between brain IDs and cognitive ability in the elderly is partially mediated by WMHs, with this mediation mainly arising from the iron deposition load in the brain stem. IDs might be an indicator of small vessel disease that predisposes to white matter damage, affecting the neuronal networks underlying higher cognitive functioning.

HydroCoils Are Associated with Lower Angiographic Recurrence Rates Than Are Bare Platinum Coils in Treatment of "Difficult-to-Treat" Aneurysms: A Post Hoc Subgroup Analysis of the HELPS Trial

BACKGROUND AND PURPOSE

The HydroCoil Endovascular Aneurysm Occlusion and Packing Study was a randomized controlled trial that compared HydroCoils to bare platinum coils. Using data from this trial, we performed a subgroup analysis of angiographic and clinical outcomes of patients with "difficult-to-treat" aneurysms, defined as irregularly shaped and/or having a dome-to-neck ratio of <1.5.

MATERIALS AND METHODS

Separate subgroup analyses comparing outcomes of treatment with HydroCoils to that of bare platinum coils were performed for the following: 1) irregularly shaped aneurysms, 2) regularly shaped aneurysms, 3) aneurysms with a dome-to-neck ratio of <1.5, and 4) aneurysms with a dome-to-neck ratio of ≥1.5. For each subgroup analysis, the following outcomes were studied at the last follow-up (3-18 months): 1) any recurrence, 2) major recurrence, 3) re-treatment, and 4) an mRS score of ≤2. Multivariate logistic regression analysis was performed to determine if the HydroCoil was independently associated with improved outcomes in these subgroups.

RESULTS

Among the patients with an irregularly shaped aneurysm, the HydroCoil was associated with lower major recurrence rates than the bare platinum coils (17 of 66 [26%] vs 30 of 69 [44%], respectively; P = .046). Among the patients with an aneurysm with a small dome-to-neck ratio, the HydroCoil was associated with lower major recurrence rates than the bare platinum coils (18 of 73 [24.7%] vs 32 of 76 [42.1%], respectively; P = .02). No difference in major recurrence was seen between HydroCoils and bare platinum coils for regularly shaped aneurysms (42 of 152 [27.6%] vs 52 of 162 [32.1%], respectively; P = .39) or aneurysms with a large dome-to-neck ratio (41 of 145 [28.3%] vs 50 of 155 [32.3%], respectively; P = .53).

CONCLUSIONS

This unplanned post hoc subgroup analysis found that HydroCoils are associated with improved angiographic outcomes in the treatment of irregularly shaped aneurysms and aneurysms with a dome-to-neck ratio of <1.5. Because this was a post hoc analysis, these results are not reliable and absolutely should not alter clinical practice but, rather, may inform the design of future randomized controlled trials.

HydroCoils reduce recurrence rates in recently ruptured medium-sized intracranial aneurysms: a subgroup analysis of the HELPS trial

BACKGROUND AND PURPOSE

The HydroCoil Endovascular Aneurysm Occlusion and Packing Study (HELPS) was a randomized, controlled trial comparing HydroCoils with bare-platinum coils. The purpose of this study was to perform a subgroup analysis of angiographic and clinical outcomes of medium-sized aneurysms in the HELPS trial.

MATERIALS AND METHODS

Patients with medium-sized aneurysms (5-9.9 mm) were selected from the HELPS trial. Outcomes compared between the HydroCoil and bare-platinum groups included the following: 1) any recurrence, 2) major recurrence, 3) retreatment, and 4) mRS score of ≤2. Subgroup analysis by rupture status was performed. Multivariate logistic regression analysis adjusting for aneurysm neck size, shape, use of adjunctive device, and rupture status was performed.

RESULTS

Two hundred eighty-eight patients with medium-sized aneurysms were randomized (144 in each group). At 15-18 months posttreatment, the major recurrence rate was significantly lower in the HydroCoil group than in controls (18.6% versus 30.8%, P = .03, respectively). For patients with recently ruptured aneurysms, the major recurrence rate was significantly lower for the HydroCoil group than for controls (20.3% versus 47.5%, P = .003), while rates were similar between groups for unruptured aneurysms (16.7% versus 14.8%, P = .80). Multivariate analysis of patients with recently ruptured aneurysms demonstrated a lower odds of major recurrence with HydroCoils (OR = 0.27; 95% CI, 0.12-0.58; P = .0007). No difference in retreatment rates or mRS of ≤2 was seen between groups.

CONCLUSIONS

HydroCoils were associated with statistically significant and clinically relevant lower rates of major recurrence for recently ruptured, medium-sized aneurysms in the HELPS trial. Because this was not a prespecified subgroup analysis, these results should not alter clinical practice but, rather, provide insight into the design of future clinical trials comparing bare platinum with second-generation coils.

CRASH-2 (Clinical Randomisation of an Antifibrinolytic in Significant Haemorrhage) intracranial bleeding study: the effect of tranexamic acid in traumatic brain injury--a nested randomised, placebo-controlled trial

BACKGROUND

Tranexamic acid (TXA) has been shown to reduce blood loss in surgical patients and the risk of death in patients with traumatic bleeding, with no apparent increase in vascular occlusive events. These findings raise the possibility that it might also be effective in traumatic brain injury (TBI).

OBJECTIVE

The Clinical Randomisation of an Antifibrinolytic in Significant Haemorrhage Intracranial Bleeding Study (CRASH-2 IBS) was conducted to quantify the effect of an early short course of TXA on intracranial haemorrhage and new focal cerebral ischaemic lesions in patients with TBI.

DESIGN

CRASH-2 IBS was a prospective randomised controlled trial nested within the CRASH-2 trial. Randomisation was balanced by centre, with an allocation sequence based on a block size of eight. We used a local pack system that selected the lowest numbered treatment pack from a box containing eight numbered packs. Apart from the pack number, the treatment packs were identical. The pack number was recorded on the entry form, which was sent to the international trial co-ordinating centre in London, UK. Once the treatment pack number was recorded, the patient was included in the trial whether or not the treatment pack was opened or the allocated treatment started. All site investigators and trial co-ordinating centre staff were masked to treatment allocation.

SETTING

Ten hospitals: (India) Aditya Neuroscience Centre, Sanjivani Hospital, CARE Hospital, Christian Medical College, Medical Trust Hospital, Jeevan Jyoti Hospital and (Colombia) Hospital Universitario San Vicente de Paul, Hospital Pablo Tobón Uribe, Hospital Universitario San José de Popayán and Fundación Valle del Lili.

PARTICIPANTS

The trial was conducted in a subset of 270 CRASH-2 trial participants. Patients eligible for inclusion in the CRASH-2 IBS fulfilled the inclusion criteria for the CRASH-2 trial, and also had TBI [Glasgow Coma Scale score of ≤ 14 and a brain computerised tomography (CT) scan compatible with TBI]. Pregnant women and patients for whom a second brain CT scan was not possible were excluded.

INTERVENTIONS

Participants were randomly allocated to receive either a loading dose of 1 g of TXA infused over 10 minutes followed by an intravenous infusion of 1 g over 8 hours or matching placebo.

MAIN OUTCOME MEASURE

The primary outcome was the increase in size of intracranial haemorrhage growth between a CT scan at hospital admission and a second scan 24-48 hours later.

RESULTS

One hundred and thirty-three patients were allocated to TXA and 137 to placebo, of whom information on the primary (imaging) outcome was available for 123 (92%) and 126 (92%) respectively. The analysis suggested that TXA was likely to be associated with a reduction in haemorrhage growth [adjusted difference -3.8 ml, 95% credibility interval (CrI) -11.5 ml to 3.9 ml], fewer focal ischaemic lesions [adjusted odds ratio (OR) 0.54, 95% CrI 0.20 to 1.46] and fewer deaths (adjusted OR 0.49, 95% CrI 0.22 to 1.06).

CONCLUSIONS

This was the first randomised controlled study to evaluate the effect of TXA in TBI patients and it found that neither moderate benefits nor moderate harmful effects can be excluded. However, although uncertainty remains, our analyses suggest that TXA administration might improve outcome in TBI patients and provide grounds for evaluating this hypothesis in future research.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN86750102.

SOURCE OF FUNDING

This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 16, No. 13. See the HTA programme website for further project information.

Assessing the impact of the requirement for explicit consent in a hospital-based stroke study

BACKGROUND

Increasing regulation of medical research, in particular the requirement for explicit consent, may reduce the quantity and quality of clinical epidemiological research.

AIM

To assess the potential biases arising from the need for explicit consent in our hospital-based stroke research register.

DESIGN

Comparison of patients enrolled into our stroke research register with those included in a concurrent clinical stroke audit that targeted the same population but did not require explicit consent.

METHODS

We obtained the numbers of consenters, refusers and those from whom consent was not sought for various logistical reasons. We compared characteristics of participants (those eventually included in the research register) vs. non-participants.

RESULTS

Of 1228 patients included in the stroke audit during an 18-month period, 1075 (88%) were also included in the research register, with higher participation among outpatients than inpatients. Only 1% of eligible patients refused involvement in any aspect of the research register. By far the largest number of non-participants was those from whom we could not seek consent for practical reasons. Comparison of baseline characteristics showed important differences between participants and non-participants that could affect outcome.

CONCLUSION

Very few patients refused inclusion in our research register, but the need for explicit consent reduced participation and introduced bias. An opt-out system avoiding the need for explicit patient consent for minimally intrusive clinical epidemiological studies would minimize bias and reduce the considerable time and costs associated with the consent process.

Magnetic resonance perfusion diffusion mismatch and thrombolysis in acute ischaemic stroke: a systematic review of the evidence to date

BACKGROUND

The mismatch between perfusion and diffusion lesions on magnetic resonance perfusion-weighted imaging (PWI)/diffusion-weighted imaging (DWI) may help identify patients for thrombolysis. Evidence underlying this hypothesis was assessed.

METHODS

All papers describing magnetic resonance PWI/DWI findings in patients with acute ischaemic stroke, and their functional and/or radiological outcome at 1 month, with or without thrombolysis were systematically reviewed.

RESULTS

11 papers fulfilled the inclusion criteria. Among these, there were 5 different mismatch definitions and at least 7 different PWI methods. Only 3 papers including 61 patients with and 18 without mismatch provided data on mismatch, outcome and influence of thrombolysis. Mismatch (v no mismatch) without thrombolysis was associated with a non-significant twofold increase in the odds of infarct expansion (odds ratio (OR) 2.2, 95% confidence interval (CI) 0.34 to 14.1), which did not change with thrombolysis (OR 2.0, 95% CI 0.37 to 10.9). Half of the patients without mismatch also had infarct growth (with or without thrombolysis). No data were available on functional outcome.

CONCLUSIONS

Standardised definitions of mismatch and perfusion are needed. Infarct growth may occur even in the absence of mismatch. Currently, data available on mismatch are too limited to guide thrombolysis in routine practice. More data are needed from studies including patients with and without mismatch, and randomised treatment allocation, to determine the role of mismatch.

Anatomical flow phantoms of the nonplanar carotid bifurcation, part I: computer-aided design and fabrication

Doppler ultrasound is widely used in the diagnosis and monitoring of arterial disease. Current clinical measurement systems make use of continuous and pulsed ultrasound to measure blood flow velocity; however, the uncertainty associated with these measurements is great, which has serious implications for the screening of patients for treatment. Because local blood flow dynamics depend to a great extent on the geometry of the affected vessels, there is a need to develop anatomically accurate arterial flow phantoms with which to assess the accuracy of Doppler blood flow measurements made in diseased vessels. In this paper, we describe the computer-aided design and manufacturing (CAD-CAM) techniques that we used to fabricate anatomical flow phantoms based on images acquired by time-of-flight magnetic resonance imaging (TOF-MRI). Three-dimensional CAD models of the carotid bifurcation were generated from data acquired from sequential MRI slice scans, from which solid master patterns were made by means of stereolithography. Thereafter, an investment casting procedure was used to fabricate identical flow phantoms for use in parallel experiments involving both laser and Doppler ultrasound measurement techniques.

Thrombolysis (different doses, routes of administration and agents) for acute ischaemic stroke

BACKGROUND

Thrombolytic therapy is effective for acute myocardial infarction, a disease with some similarities to acute ischaemic stroke. Meta-analyses suggest a net benefit in acute ischaemic stroke.

OBJECTIVES

To assess different thrombolytic agents, and different regimens, in acute ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group trials register (last searched to June 2003), MEDLINE (1966 to July 2003) and EMBASE (1980 to July 2003). We handsearched four Japanese journals, contacted researchers and pharmaceutical companies, and attended relevant conferences.

SELECTION CRITERIA

Randomised and quasi-randomised trials of different doses of a thrombolytic agent, or different agents, or the same agent given by different routes, in people with confirmed acute ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial eligibility and quality, and extracted the data.

MAIN RESULTS

Ten trials involving 1641 patients, 8 conducted in Japan, 1 in China and 1 in the USA, were included. Concealment of allocation was poorly described. Different doses (of tissue plasminogen activator or urokinase) were compared in seven trials (n = 1072 patients). Different agents (tissue plasminogen activator versus urokinase; tissue-cultured urokinase versus conventional urokinase) were compared in three trials (n = 688 patients). One trial compared different routes of administration (intravenous plus intraarterial tissue plasminogen activator versus intraarterial tissue plasminogen activator alone, n = 35 patients). As some trials compared different agents and different doses, some patients contributed to two analyses. A higher dose of thrombolytic therapy was associated with a three-fold increase in fatal intracranial haemorrhages (Odds ratio (OR) 3.25, 95% confidence interval (CI) 1.32 to 7.97) compared with a lower dose of the same agent (based on 16 events among 539 higher-dose patients and 4 events among 533 lower-dose patients in 7 trials). There was no statistically significant difference in early (OR 1.01, 95% CI 0.58 to 1.74) or late (OR 0.94, 95% CI 0.58 to 1.53) deaths between lower and higher doses. Data were inadequate to assess the effect of dose on functional outcome. No statistically significant difference was shown between different thrombolytic agents tested. The data from the pilot trial comparing different routes of administration were inconclusive.

REVIEWERS' CONCLUSIONS

These scant data suggest that higher doses of thrombolytic agents may lead to higher rates of bleeding. However, the evidence is inadequate to conclude whether lower doses of thrombolytic agents are more effective than higher doses, or whether one agent is better than another, or which route of administration is the best, in acute ischaemic stroke.

Low myo-inositol and high glutamine levels in brain are associated with neuropsychological deterioration after induced hyperammonemia

The neuropsychological effect of hyperammonemia is variable. This study tests the hypothesis that the effect of ammonia on the neuropsychological function in patients with cirrhosis is determined by the ability of the brain to buffer ammonia-induced increase in glutamine within the astrocyte by losing osmolytes like myo-inositol (mI) and not by the magnitude of the induced hyperammonemia. Fourteen cirrhotic patients with no evidence of overt hepatic encephalopathy were given a 75-g amino acid (aa) solution mimicking the hemoglobin molecule to induce hyperammonemia. Measurement of a battery of neuropsychological function tests including immediate memory, ammonia, aa, and short-echo time proton magnetic resonance spectroscopy were performed before and 4 h after administration of the aa solution. Eight patients showed deterioration in the Immediate Memory Test at 4 h. Demographic factors, severity of liver disease, change in plasma ammonia, and aa profiles after the aa solution were similar in those that showed a deterioration compared with those who did not. In patients who showed deterioration in the memory test, the mI-to-creatine ratio (mI/Cr) was significantly lower at baseline than those that did not deteriorate. In contrast, the glutamate/glutamine-to-Cr ratio was significantly greater in the patients that deteriorated. The observation that deterioration in the memory test scores was greater in those with lower mI/Cr supports the hypothesis that the neuropsychological effects of induced hyperammonemia is determined by the capacity of the brain to handle ammonia-induced increase in glutamine.

Fibrinogen depleting agents for acute ischaemic stroke

BACKGROUND

Fibrinogen depleting agents reduce fibrinogen in blood plasma, reduce blood viscosity and hence increase blood flow. This may help remove the blood clot blocking the artery and re-establish blood flow to the affected area of the brain after an ischaemic stroke. The risk of haemorrhage may be less than with thrombolytic agents.

OBJECTIVES

The objective of this review was to assess the effect of fibrinogen depleting agents in patients with acute ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched May 2003). In addition we searched the following electronic databases: EMBASE (1980-October 2001), China Biological Medicine Database (CBM-disc 1981- December 2002), Chinese Stroke Trials Register (1996 - December 2002) and Index of Scientific and Technical Proceedings (Web of Science Proceedings [1990-October 2001]). We handsearched relevant journals and contacted Chinese and Japanese researchers and drug companies.

SELECTION CRITERIA

Randomised and quasi-randomised trials of fibrinogen depleting agents started within 14 days of stroke onset, compared with control in patients with definite or possible ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two reviewers independently applied the inclusion criteria, assessed trial quality and extracted the data.

MAIN RESULTS

Five trials involving 2926 patients were included. A further trial (ESTAT) has not yet been published in full. Four trials tested ancrod and one trial tested defibrase. Allocation concealment was adequate in four trials. Fibrinogen depleting agents moderately reduced the proportion of patients who were dead or disabled at the end of follow up (Relative risk [RR] 0.90, 95% Confidence Interval [CI] 0.82 to 0.98, 2P=0.02). There was no statistically significant difference in death from all causes during the scheduled treatment period (RR 0.71, 95% CI 0.44 to 1.13) and at the end of follow-up (RR 0.98, 95% CI 0.78 to 1.24). There was a non-significant excess of symptomatic intracranial haemorrhages with treatment (RR 2.64, 95%CI 0.96 to 7.30, 2P=0.06).

REVIEWER'S CONCLUSIONS

Fibrinogen depleting agents are promising. However more data, particularly ESTAT data, are needed before more reliable conclusions can be drawn.

Increased blood-brain barrier permeability in type II diabetes demonstrated by gadolinium magnetic resonance imaging

OBJECTIVES

Patients with type II diabetes are at increased risk of cognitive impairment. The retinal and renal complications of diabetes follow microvascular damage permitting small arterioles to leak, hence the cerebral damage might also follow loss of blood-brain barrier (BBB) integrity. Magnetic resonance (MR) brain imaging with intravenous gadolinium (Gd) diethylenetriamine pentaacetic acid (Gd-DTPA) was used to identify increased BBB permeability.

METHODS

Ten well controlled type II diabetic patients aged 65-70 years and 10 controls underwent MR brain imaging with fluid attenuated inversion recovery (FLAIR); T1 weighted (T1W) volumetric imaging before; and T1W volumetric imaging at 5, 15, 30, 45, 60, and 90 minutes after intravenous Gd-DTPA. The T1W image before Gd-DTPA was subtracted from the images at each time point after Gd-DTPA. Net signal intensity was plotted against time for different brain regions. White matter hyperintensities were scored from the FLAIR image.

RESULTS

The signal intensity/time curves showed that brain signal intensity increased more in the diabetic group than controls during the first 15 minutes after Gd-DTPA, particularly in the basal ganglia (p=0.018). Signal intensity in controls peaked at five minutes and diabetics at 15 minutes. Subjects with more white matter hyperintensities had greater signal increase after Gd-DTPA, whether diabetic or not (p=0.001).

CONCLUSIONS

Increased BBB permeability with MR imaging was detected in patients with type II diabetes or white matter hyperintensities. Increased permeability of the BBB might account for some of the cerebral effects of type II diabetes, and so possibly also for the effect of other conditions that affect the microvasculature (like hypertension), on the brain.

Repeatability of long and short echo-time in vivo proton chemical-shift imaging

We carried out long (145 ms) and short (25 ms) echo time spectroscopic imaging of the brain (chemical-shift imaging, CSI) on two occasions 1 week apart on 15 healthy individuals. We found coefficients of variation (CVs) generally in the range 10-25% for long and 15-30% for short echo-time measurements. The CVs of metabolite ratios were higher by about 5-10%. Limits of agreement (defined as mean+/-2 SD of the week 1-week 2 differences) were wider at the shorter echo time. The modest repeatability may be due in part to the difficulty of repositioning spectroscopic voxels at a scale of 1 mm. The generally higher CVs and wider limits of agreement at TE25 ms suggest that the increased spectral complexity more than offsets the theoretical advantage of increased signal at short echo-times. Analysis of variance general linear modelling of metabolites and metabolite ratios showed that, in general, the subject, region of the brain and hemisphere were more important than the occasion in explaining the variability of results. Unless information on short-T2 metabolites is specifically required, better results can probably be achieved with longer echo-times. The magnitude of the CVs needs to be taken into account in the calculation of sample size for cross-sectional or linear studies.

Magnetic resonance brain imaging in people with dizziness: a comparison with non-dizzy people

BACKGROUND

Dizziness is a common symptom affecting about 30% of people over the age of 65.

OBJECTIVE

To investigate the hypothesis that structural abnormalities of the brain and cervical cord are more common in dizzy than in non-dizzy subjects.

METHODS

A case-control study of subjects over the age of 65 with and without dizziness: 125 dizzy subjects and 86 non-dizzy subjects were recruited from the community through articles in the local press. Magnetic resonance imaging (MRI) of the brain and neck was performed, and was read by a consultant neuroradiologist blind to the clinical details.

RESULTS

All dizzy subjects and all controls had at least one structural abnormality. Cerebral atrophy was found in 86% of dizzy subjects and 85% controls (p = 1.0) At least one white matter lesion was found in 69% of dizzy subjects and 78% controls (p = 0.21). White matter lesions in the midbrain were more common in dizzy than in non-dizzy subjects (22% v 4%, p < 0.001). There were no significant differences in the prevalence of cord compression, cervical subluxation, facet joint degeneration, vertebral artery compression, or vertebral artery occlusion between dizzy and non-dizzy subjects.

CONCLUSIONS

Structural abnormalities of the brain and neck are common in both dizzy and non-dizzy subjects. "Routine" MRI is unlikely to reveal a specific cause for dizziness. The observation of more frequent white matter lesions in the midbrain in dizzy subjects requires further study to determine whether small vessel changes could cause dizziness in older people.

Critical appraisal of the design and reporting of studies of imaging and measurement of carotid stenosis

BACKGROUND AND PURPOSE

Several hundred studies have been published over the last few years on imaging and measurement of carotid stenosis. Despite all this research, there is still no consensus about how best to image and measure stenosis. One possible explanation for this is that many of the studies have not been large enough or methodologically sound enough to allow useful conclusions to be drawn. We aimed to assess the design and methods of a random sample of published studies of imaging and measurement of carotid stenosis using 9 simple criteria.

METHODS

A formal literature search was performed for studies of imaging and measurement of carotid stenosis. Two subsets were randomly selected for detailed assessment: 20 studies published before 1991 and 20 published between 1993 and 1997 (some years after the initial publication of the ECST and NASCET trials). The criteria used to assess the selected studies were as follows: prospective rather than retrospective study design; patient selection based on a consecutive series or a random sample; adequate detail of study population; adequate detail of imaging techniques; inclusion of all investigations, ie, patients with poor-quality imaging were not excluded; blinded assessment of images; adequate detail of derivation of measurement of stenosis from images or data; adequate data on the reproducibility of measurements of stenosis; and study powered according to a sample-size calculation.

RESULTS

There were many basic methodological deficiencies in both subsets of studies, with relatively little evidence of improvement with time. For example, only 33% of studies were prospective, only 45% studied a consecutive or random selection of patients, and only 38% reported any data on the reproducibility of measurements. More than half of the studies satisfied < or =4 of the 9 quality criteria. However, there was considerable variation between studies, with 7 studies satisfying > or = 7 criteria and 10 studies satisfying < or =2. No study was based on a sample-size calculation. The number of patients studied was often small, particularly in the more recent studies: median sample size was 100 in the 1970-1990 studies and 58 in the 1993-1997 studies (P<0.0001).

CONCLUSIONS

The design and reporting of published studies of imaging and measurement of carotid stenosis are poor and have not improved much in recent years. The majority of published studies are not of a sufficient standard to enable the results to be used to inform clinical practice. The utility of future studies could be improved considerably by better adherence to 9 simple methodological guidelines.

What pathological components indicate carotid atheroma activity and can these be identified reliably using ultrasound?

OBJECTIVE

The aim of this project was to determine whether histological features of 'active' plaque as described in the coronary circulation following acute myocardial infarction were similar in the carotid circulation, and whether these factors could be detected ultrasonically.

METHOD

Endarterectomy specimens were prospectively collected, and examined histologically and assessed by two observers for ulceration, inflammation, size of necrotic core, thickness of fibrous cap, haemorrhage and luminal thrombosis. Ultrasound of the plaque obtained preoperatively was similarly coded (blind to pathology) and compared with the pathology.

RESULTS

In 42 endarterectomy specimens, there was a highly significant relationship between a thin fibrous cap and a large necrotic core (P<0.002), irregular plaque contour (P<0.05) and ulceration (P<0.01) and between a large necrotic core (P<0.002) and ulceration and inflammation (P<0.05). Increasing amounts of necrosis were associated with more surface thrombosis (P<0.02). Ultrasound detected the thickness of the fibrous cap and 'any necrosis or haemorrhage' with some reliability (kappas are 0.53 and 0.5, respectively), but not ulceration, necrosis or haemorrhage on their own.

CONCLUSION

Features corresponding to active atheromatous plaque are similar in the carotid and coronary arteries, and some of these, namely lucent areas in the plaque (corresponding to necrosis or haemorrhage) and the thickness of the fibrous cap, can be determined reliably with ultrasound.

Thrombolysis (different doses, routes of administration and agents) for acute ischaemic stroke

BACKGROUND

Thrombolytic therapy is effective for acute myocardial infarction, a vascular disease with some similarities to acute ischaemic stroke.

OBJECTIVES

The objective of this review was to assess the effect of different thrombolytic agents, and different regimens in acute ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group trials register and Embase (1980 to 1997). We handsearched Japanese and Chinese journals. We contacted researchers in the field and pharmaceutical companies.

SELECTION CRITERIA

Randomised and quasi-randomised trials of different doses of a thrombolytic agent, or one thrombolytic agent compared with another, or the same agent given by different routes, in people with confirmed acute ischaemic stroke. Trials were included if treatment was started within 14 days of stroke onset.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed eligibility, trial quality and extracted the data.

MAIN RESULTS

Eight trials involving 1334 people were included. Concealment of allocation was generally adequate. All the trials were conducted in Japan. Different doses (of tissue plasminogen activator or urokinase) were compared in seven trials. Different agents (tissue plasminogen activator versus urokinase, or tissue-cultured urokinase versus conventional urokinase) were compared in three trials. Few data were available for functional outcomes. A higher dose of thrombolytic therapy was associated with a five-fold increase in fatal intracranial haemorrhages (odds ratio 5.02, 95% confidence interval 1.56 to 16. 18). This was based on 11 events among 369 higher-dose patients and one event among 356 lower-dose patients in six trials. There was a non-significant trend towards more early deaths or clinically significant intracranial haemorrhages. No difference in late deaths or extra-cranial haemorrhages was shown between low and higher doses. However, very few of these events occurred. No difference was shown between the different thrombolytic agents tested.

REVIEWER'S CONCLUSIONS

There is not enough evidence to conclude whether lower doses of thrombolytic agents might be safer or more effective than higher doses in acute ischaemic stroke. It is not possible to conclude whether one agent might be better than another, or which route of administration might be best. No comparative data for streptokinase have been found.

Families of trials: the answers to all our questions?

Many of the important clinical decisions we make on a daily basis in stroke medicine are not supported by adequate evidence. This leads to variations in practice. If practice influences outcome, this must be regarded as unacceptable since it implies that many patients are receiving sub-optimal treatment. Where the advantages of certain treatment policies over others are only moderate, large randomised clinical trials provide the most reliable evidence of effectiveness. However, only a tiny proportion of patients with stroke are randomised in trials. Instead, the majority are exposed to treatments allocated haphazardly, rather than randomly, which serves only to delay the emergence of evidence concerning the relative merits of alternative treatment approaches. We suggest that we might increase the proportion of patients who contribute to advancing our knowledge by developing 'families' of trials. A 'family' would comprise a series of randomised trials into which patients with stroke may be enrolled either simultaneously or sequentially into one or more of the trials which would share common systems for randomisation and follow-up. Such a system would facilitate large, simple, randomised trials, reduce research costs, increase the generalisability of trial results and allow clinicians and patients to contribute to advancing our knowledge whenever they are uncertain about the best treatment. In this article, we discuss the advantages of this approach, some of the problems and their potential solutions.

Dsyembryoplastic neuroepithelial tumour with discrete bilateral multifocality: further evidence for a germinal origin

We report the case of a middle aged woman who developed refractory complex partial seizures in her early twenties. She had a right coloboma and neurological examination was normal. Neuropsychological assessments revealed mild impairments of non-verbal memory, and visuospatial and constructional difficulties. Serial CT and MRI showed multiple nodular abnormalities in her mid-brain, diencephalon, subependymal region and both mesial temporal lobes. EEG recording revealed a right medial temporal focus. She underwent en bloc temporal lobectomy. The surgical pathology revealed mesial temporal dysembryoplastic neuroepithelial tumour (DNET) in association with extensive, contiguous neocortical dysplasia. The proliferation marker MIB-1 revealed up to 2% labelling in tumour areas resembling conventional oligodendroglioma. In the two years since surgery she has been seizure free and the remaining MR brain abnormalities have not changed. The very unusual centripetal MRI pattern of discrete multifocal lesions with the characteristic T1 and T2 features of DNET would support the dysembyroplastic germinal origin that was proposed by Daumas-Duport et al. (1988) in their original description of the lesion. The neuroradiological, neuropathological and clinical features of this case are compared with the two previous cases of multifocal DNET.

Delays in stroke referrals

Assessment of acute stroke by hospital physicians will have to speed up if we are to expect referral to hospital and computed tomography (both previously targets of criticism) to improve.

Atherosclerotic plaque at the carotid bifurcation: CT angiographic appearance with histopathologic correlation

BACKGROUND AND PURPOSE

The likelihood that carotid plaque will give rise to cerebral ischemia probably relates to the degree of arterial stenosis and to plaque morphology. The aim of this study was to assess whether features seen at CT angiography might be used to predict carotid plaque stability by comparing CT angiograms with histopathologic examinations of the carotid artery bifurcation.

METHODS

Nine patients with symptomatic severe carotid stenosis at intraarterial angiography had CT angiography of the carotid bifurcation before carotid endarterectomy. After endarterectomy, multiple sections of the specimens through the carotid bifurcation were examined histologically. Plaque characteristics recorded included the proportion of necrotic/lipid core, presence of hemorrhage, extent of fibrosis, ulceration, calcification, inflammatory cell infiltrate, and fibrous cap thickness. Corresponding CT angiograms were assessed for plaque size, distribution, and radiodensity as well as presence of calcific density and ulceration. Histologic findings and CT angiograms were compared.

RESULTS

Plaque with a large necrotic/lipid core, which was often hemorrhagic, was found in 16 of 23 sections, and in 15 of these this histologic appearance corresponded with patchy or homogeneous low density on CT angiograms. Six of seven predominantly fibrous plaques were of soft-tissue density on CT angiograms. High density consistent with calcification was seen more frequently on CT angiograms than it was detected histologically, but CT angiography depicted plaque ulceration poorly (four ulcers at histology; two false-positive and two false-negative findings at CT angiography).

CONCLUSION

CT angiography is a promising method for assessing the lumen and wall of the carotid artery. The apparent correlation between histologic appearance and plaque density on CT angiograms has important implications for the prediction of plaque stability, even though ulceration is shown inconsistently.

Thrombo-embolic stroke, moya-moya phenomenon and primary oxalosis

We present the clinical, radiological and autopsy findings in a 32-year-old woman with primary oxalosis, who suffered recurrent bilateral carotid territory infarcts. The overall features were those of moya-moya syndrome, with bilateral, ultimately thrombotic, occlusion of the distal internal carotid arteries. Vessel pathology suggests an underlying intimal vasculopathy, the possible relation of which to the patient's metabolic abnormality is discussed.

A flow model of cerebral aneurysms for use with power Doppler studies

It has recently been observed using power Doppler that cerebral aneurysms appear to change size through the cardiac cycle. The purpose of this study was to develop a pulsatile flow model of cerebral aneurysm expansion and to investigate whether the observations of pulsation could be confirmed using the model. The model consisted of a latex bubble glued onto the side of a latex tube. A computer controlled pump was used to generate pulsatile flow. The degree of bubble expansion was adjusted by the use of flow restrictor placed in the downstream section of the flow rig. Ultrasound images were acquired using an Acuson 128 XP/10V colour flow scanner. True expansion (maximum area/minimum area) was measured from the B-scan image using a 7 MHz probe. Three observers measured expansion of the simulated aneurysm from the power Doppler images using a 2 MHz probe. Expansion measured with the power Doppler decreased as the colour gain setting increased, and decreased as the persistence increased. The true expansion of 1.43 was comparable with the colour gain set optimally for a persistence value of 3. The model allows simple investigations of the relationship between true aneurysm expansion and that measured from the power Doppler images. Colour gain and persistence settings must be standardized in clinical studies.

A systematic review of randomized evidence for fibrinogen-depleting agents in acute ischemic stroke

OBJECTIVE

To assess the efficacy and safety of fibrinogen-depleting agents (snake venom extracts) in the treatment of acute ischemic stroke.

METHODS

A systematic review of all the relevant randomized controlled trials (RCTs) was performed. RCTs were identified from the Cochrane Stroke Group's Specialized Trial Register, additional electronic and hand searching, and personal contact with pharmaceutical companies. We included all completed and unconfounded truly or quasi-randomized trials in patients with ischemic stroke comparing fibrinogen depleting agents with control started within 14 days of the stroke onset. The Peto method was used for analysis.

RESULTS

Eight completed and two ongoing RCTs have been identified so far. Only three trials using ancrod (182 patients) met the inclusion criteria. Ancrod was associated with a significant reduction in early deaths (5.6% v 16%; odds ratio [OR], 0.33; 95% confidence interval [CI], 0.13 to 0.85; 2P=.02) suggesting that treatment of 100 patients would avoid about 10 early deaths. The frequency of asymptomatic intracranial hemorrhage shown by computed tomography was similar between ancrod-treated and control groups (7.6% v 9.6%; OR, 0.78; 95% CI, 0.26 to 2.33; 2P=.65). No major intracranial or extracranial hemorrhages or recurrent ischemic strokes occurred in the ancrod-allocated patients. There were nonsignificant trends in favor of ancrod in death from any cause (OR, 0.57; 95% CI, 0.27 to 1.23; 2P=.15) and death or disability (OR, 0.52; 95% CI, 0.26 to 1.03; 2P=.06) at the end of trial follow-up.

CONCLUSIONS

There were too few patients and outcome events to draw reliable conclusions from the present data. Although ancrod-like agents appeared promising, their routine use cannot be recommended at the moment. Two ongoing trials (including about 1,000 patients in total) will provide more data. Future trials should test simpler fixed-dose regimens to allow better generalizability.

The drug trials that have influenced our clinical practice in acute ischaemic stroke

With the possible exception of aspirin, there are still no drug treatments which have been found to be so effective in randomised controlled trials, and meta-analyses of such trials, that they should be used routinely in acute ischaemic stroke. The evidence on thrombolysis is tantalising but with only about 3500 randomised patients in all the trials put together it is too early to say how, and for whom, this promising treatment should be used, particularly bearing in mind the risk of intracranial haemorrhage; the evidence so far is enough to persuade us to enter our patients into further large trials of thrombolysis but it is not enough to justify this treatment in our routine clinical practice.

Reproducibility of metabolite peak areas in 1H MRS of brain

We studied the reproducibility of metabolite signals (from N-acetyl aspartate [NAA], choline, and creatine) measured with a standard single-voxel proton magnetic resonance spectroscopy technique (PRESS, TE = 135 ms, 8 ml VOI) in vitro and in two groups of normal volunteers. Spectral peak areas were quantified both by integration and by curve-fitting. In the in vitro study, the "between-days" variability (coefficient of variation [CV]) of measurements ranged from 0.9% to 2.3%. In the first group of volunteers (n = 12), single voxel spectroscopic measurements (8 ml VOI, 256 acquisitions [ACQs]) were made from mirror-image parts of the right and left hemispheres on 2 separate days. The "between-days" CV of measurements ranged from 9% to 18% for metabolite areas, and from 10% to 26% for metabolite area ratios. There were no significant differences between quantification method or hemisphere. After checking and optimising the MR scanner performance (in fact, it was virtually optimal), the second group (n = 4) each had six sequential single voxel spectroscopic measurements (each of 64 ACQs) from the right hemisphere (without moving the voxel) on each of 4 separate days. Even when the metabolites were measured from the same place in the same hemisphere sequentially six times in a 20-min period, the "within-run" CVs ranged from 4.4% to 17.2% for metabolite areas and from 9.7% to 17.0% for metabolite area ratios. The between-days CVs for the subjects ranged from 7.7% to 25.8% (metabolite areas) and from 10.1% to 22.6% (metabolite area ratios). The variability is due to a combination of random noise, subject motion, baseline artefacts in the spectra, and uncertainties in repositioning the VOIs. It is likely to represent the best reproducibility possible with 8-ml VOIs in cooperative, healthy volunteers carefully positioned on each occasion in a standard clinical scanner. Changes in metabolite levels in individuals must therefore be of the order of 20-40% before we can be reasonably confident of measuring them. Reproducibility in patients, who may be less cooperative, will probably be no better, and this must be taken into account in the interpretation of MRS studies in patients with brain pathology; for example, stroke, head injury, and tumours.

Panhypopituitarism after cavernous sinus thrombosis

Images

Antiplatelet, anticoagulant and fibrinolytic agents in acute ischaemic stroke and TIA

In acute ischaemic stroke and transient ischaemic attacks both platelets and coagulation factors are activated. This is the rationale for the use of antiplatelet and anticoagulant agents in the prevention of acute ischaemic stroke. Evidence also suggests that antiplatelet agents anticoagulants and dissolution of a thrombus occluding a major cerebral vessel (by means of fibrinolytic agents) may be beneficial as therapy for the acute phase of ischaemic stroke.