Can We Miniaturize CT Technology for a Successful Mobile Stroke Unit Roll-Out?

Mortality from stroke remains high in Australia, especially for patients located outside the metropolitan cities. This is because they have limited access to specialized stroke facilities for optimal stroke treatment. Mobile stroke units have the capability to take CT scanners out to the patient however current CT commercial scanner designs are large and heavy. As such, this paper aims to design and develop a lightweight CT scanner for use in a mobile stroke unit (either road-based or air-based ambulance) to bring healthcare solution to patients in the rural and remote areas. We used the engineering design optimization approach to redesign and reduce the weight of the existing CT scanner with without compromised it structural performance. We managed to reduce the weight the CT scanner by three-fold while reducing design costs by allowing numerous simulations to be performed using computer software to achieve our design goals. The results are not only useful to optimize CT scanner structure to retrofit on a mobile stroke unit, but also bring the medical device solution to the market and support scalable solution to the larger community. Such an advance will allow for improved equity in healthcare whereby patients can be treated irrespective of location.

ICARUSS, the Integrated Care for the Reduction of Secondary Stroke trial: rationale and design of a randomized controlled trial of a multimodal intervention to prevent recurrent stroke in patients with a recent cerebrovascular event, ACTRN = 12611000264987

BACKGROUND

The majority of strokes, both ischaemic and haemorrhagic, are attributable to a relatively small number of risk factors which are readily manageable in primary care setting. Implementation of best-practice recommendations for risk factor management is calculated to reduce stroke recurrence by around 80%. However, risk factor management in stroke survivors has generally been poor at primary care level. A model of care that supports long-term effective risk factor management is needed.

AIM

To determine whether the model of Integrated Care for the Reduction of Recurrent Stroke (ICARUSS) will, through promotion of implementation of best-practice recommendations for risk factor management reduce the combined incidence of stroke, myocardial infarction and vascular death in patients with recent stroke or transient ischaemic attack (TIA) of the brain or eye.

DESIGN

A prospective, Australian, multicentre, randomized controlled trial.

SETTING

Academic stroke units in Melbourne, Perth and the John Hunter Hospital, New South Wales.

SUBJECTS

1000 stroke survivors recruited as from March 2007 with a recent (<3 months) stroke (ischaemic or haemorrhagic) or a TIA (brain or eye).

RANDOMIZATION

Randomization and data collection are performed by means of a central computer generated telephone system (IVRS).

INTERVENTION

Exposure to the ICARUSS model of integrated care or usual care.

PRIMARY OUTCOME

The composite of stroke, MI or death from any vascular cause, whichever occurs first.

SECONDARY OUTCOMES

Risk factor management in the community, depression, quality of life, disability and dementia.

STATISTICAL POWER

With 1000 patients followed up for a median of one-year, with a recurrence rate of 7-10% per year in patients exposed to usual care, the study will have at least 80% power to detect a significant reduction in primary end-points

CONCLUSION

The ICARUSS study aims to recruit and follow up patients between 2007 and 2013 and demonstrate the effectiveness of exposure to the ICARUSS model in stroke survivors to reduce recurrent stroke or vascular events and promote the implementation of best practice risk factor management at primary care level.

Salvage of the PWI/DWI mismatch up to 48 h from stroke onset leads to favorable clinical outcome

BACKGROUND AND PURPOSE

In acute ischemic stroke perfusion/diffusion-weighted image, mismatch using magnetic resonance imaging approximates the ischemic penumbra. For early time windows, mismatch salvage improves clinical outcomes, but uncertainty exists at later time epochs. We hypothesized that (a) mismatch may exist up to 48 h; (b) the proportion of mismatch salvage is time independent; and (c) when salvaged, it improves clinical outcomes.

METHODS

Magnetic resonance imaging was performed within 48 h of ischemic stroke. Perfusion-weighted image was defined by relative Tmax two-second delay. Perfusion/diffusion-weighted image mismatch was the perfusion-weighted image not overlapped by the diffusion-weighted image when coregistered. Infarct volume and disability (modified Rankin Score) were assessed at three-months. Mismatch salvage was the region not overlapped by final infarction. Favorable outcome was defined as modified Rankin Score 0-1.

RESULTS

Sixty-six patients were studied [mean age 69.9 years (standard deviation 13.1), initial median National Institute of Health Stroke Scale 9.0 (interquartile range 6.0, 18.3)]. There was no relationship between time of stroke onset and the proportion of mismatch salvaged (P = 0.73). Age (adjusted odds ratio = 0.92, 95% confidence interval 0.86-0.98, P = 0.01), initial National Institute of Health Stroke Scale (adjusted odds ratio = 0.80, 95% confidence interval 0.70-0.92, P < 0.01), mismatch volume (adjusted odds ratio = 0.98, 95% confidence interval 0.968-0.1, P = 0.05), and percentage of mismatch salvage (adjusted odds ratio = 1.04, 95% confidence interval 0.99-1.07, P = 0.05) were independently associated with favorable outcome.

CONCLUSION

Using coregistered perfusion/diffusion-weighted image criteria, mismatch persists up to 48 h post stroke. For the whole group, the proportion of mismatch salvage remains independent of time and, although the effect is small, its salvage is independently associated with improved clinical outcomes at three-months. Larger sample sizes are needed to determine the time limit for mismatch salvage.

Atheroma of the aortic arch: the missing link in the secondary prevention of stroke?

Atheroma of the aortic arch is an important risk factor for stroke and for recurrent stroke. Optimal management is not known but these patients should probably receive more powerful antiplatelet treatment than aspirin alone. Whether combination treatment with aspirin plus clopidogrel is more effective than warfarin alone is the subject of the ongoing ARCH study.

Ischemic diffusion lesion reversal is uncommon and rarely alters perfusion-diffusion mismatch

OBJECTIVE

The use of diffusion-weighted imaging (DWI) to define irreversibly damaged infarct core is challenged by data suggesting potential partial reversal of DWI abnormalities. However, previous studies have not considered infarct involution. We investigated the prevalence of DWI lesion reversal in the EPITHET Trial.

METHODS

EPITHET randomized patients 3-6 hours from onset of acute ischemic stroke to tissue plasminogen activator (tPA) or placebo. Pretreatment DWI and day 90 T2-weighted images were coregistered. Apparent reversal of the acute ischemic lesion was defined as DWI lesion not incorporated into the final infarct. Voxels of CSF at follow-up were subtracted from regions of apparent DWI lesion reversal to adjust for infarct atrophy. All cases were visually cross-checked to exclude volume loss and coregistration inaccuracies.

RESULTS

In 60 patients, apparent reversal involved a median 46% of the baseline DWI lesion (median volume 4.9 mL, interquartile range 2.6-9.5 mL) and was associated with less severe baseline hypoperfusion (p < 0.001). Apparent reversal was increased by reperfusion, regardless of the severity of baseline hypoperfusion (p = 0.02). However, the median volume of apparent reversal was reduced by 45% when CSF voxels were subtracted (2.7 mL, interquartile range 1.6-6.2 mL, p < 0.001). Perfusion-diffusion mismatch classification only rarely altered after adjusting the baseline DWI volume for apparent reversal. Visual comparison of acute DWI to subacute DWI or day 90 T2 identified minor regions of true DWI lesion reversal in only 6 of 93 patients.

CONCLUSIONS

True DWI lesion reversal is uncommon in ischemic stroke patients. The volume of apparent lesion reversal is small and would rarely affect treatment decisions based on perfusion-diffusion mismatch.

Multidisciplinary approach to carotid stenting

BACKGROUND

Stroke neurologists, vascular surgeons, interventional neuroradiologists and interventional cardiologists have embraced carotid angioplasty and stenting (CAS) because of potential advantages over carotid endarterectomy (CEA). At Austin Health, a multidisciplinary neuro-interventional group was formed to standardise indications and facilitate training. The aims of this study were to describe our organisational model and to determine whether 30-day complications and early outcomes were similar to those of major trials.

METHODS

A clinical protocol was developed to ensure optimal management. CAS was performed on patients with high medical risk for CEA, with technically difficult anatomy for CEA, or who were randomised to CAS in a trial.

RESULTS

From October 2003 to May 2008, 47 patients (34 male, mean age 71.5) underwent CAS of 50 carotid arteries. Forty-three cases had ipsilateral carotid territory symptoms within the previous 12 months. The main indications for CAS were high risk for CEA (n= 17) and randomised to CAS (n= 21). Interventionists were proctored in 27 cases. The procedural success rate was 94% with two cases abandoned because of anatomical problems and one because of on-table angina. Hypotension requiring vasopressor therapy occurred in 12 cases (24%). The duration of follow up was one to 44 months (mean 6.8 months). The 30-day rate of peri-procedural stroke or death was 6% and the one-year rate of peri-procedural stroke or death or subsequent ipsilateral stroke was 10.6%. Restenosis occurred in 13% (all asymptomatic).

CONCLUSION

A multidisciplinary approach is a useful strategy for initiating and sustaining a CAS programme.

The Virtual International Stroke Trials Archive (VISTA): Results and Impact on Future Stroke Trials and Management of Stroke Patients

Background

The Virtual International Stroke Trials Archive was established to improve stroke care and trial design through the collation, categorization and potential access to data sets from clinical trials for the treatment of stroke.

Methods

Virtual International Stroke Trials Archive currently provides access to a combined data set of 29 anonymised acute stroke trials and one acute stroke registry with data on >27 500 patients aged between 18 and 103 (mean 71) years.

Results

Virtual International Stroke Trials Archive has facilitated research across a broad canvas. The prognosis was poor in patients with very high blood pressure at the time of admission or with a wide variability of systolic blood pressure during the acute phase. The late occurrence of hyperthermia following an ischaemic stroke worsens the prognosis. Stroke lateralisation is not an important predictor of cardiac adverse events or 90-day mortality. Haemorrhagic transformation is seen frequently in patients with cardio-embolic strokes and is associated with a poor prognosis when occurring after the acute phase. Virtual International Stroke Trials Archive has allowed various prognostic models for patients with ischaemic or haemorrhagic stroke to be established and validated. More direct outcomes such as lesion volume can be useful in phase II clinical trials for determining whether a phase III trial should be undertaken. New outcome measures such as ‘home time’ may also strengthen future trials. On a worldwide level, the prognosis of stroke patients differs considerably between various countries.

Conclusion

Virtual International Stroke Trials Archive provides an excellent opportunity for analysis of natural history data and prognosis. It has the potential to influence clinical trial design and implementation through exploratory data analyses.

Baseline diabetic status and admission blood glucose were poor prognostic factors in the EPITHET trial

BACKGROUND

Previous data have suggested that diabetes and hyperglycemia predict poor outcome following stroke. We studied the prognostic impact of diabetes and admission blood glucose in the Echoplanar Imaging Thrombolytic Evaluation Trial (EPITHET).

METHODS

EPITHET was a prospective randomized placebo-controlled trial of intravenous tissue plasminogen activator (tPA) in the 3- to 6-hour time window. A preexisting diagnosis of diabetes was noted and baseline serum glucose was measured.

RESULTS

Intravenous tPA attenuated infarct growth in non-diabetics, but not in diabetics (p = 0.029). In the tPA treatment group, admission blood glucose was higher among patients with poor functional outcome (p = 0.002).

CONCLUSIONS

Diabetes and hyperglycemia attenuate the effects of tPA on infarct evolution. Future thrombolytic trials should consider randomizing patients by subgroups based on diabetic status and serum glucose levels.

Hypertension and TIA

Transient ischemic attack is a medical emergency because early stroke risk after transient ischemic attack is high. Hypertension is the most important modifiable risk factor for stroke and transient ischemic attack. The aims of this review are to provide a summary of the current knowledge concerning the relationship between blood pressure and transient ischemic attack, as well as outline issues regarding diurnal variation and the potential of chronotherapy (timing medications to accord with diurnal patterns of blood pressure). There is a strong relationship between hypertension and the incidence of transient ischemic attack and the subsequent short-term risk for stroke. Ambulatory blood pressure monitoring is a reliable diagnostic and monitoring tool for hypertension and provides additional information about diurnal variation in blood pressure. Different diurnal blood pressure patterns may confer variable stroke risk. Patients with stroke commonly have abnormal diurnal blood pressure patterns and this may relate, in part, to autonomic nervous system dysfunction. However, blood pressure patterns have not been systematically studied in patients with transient ischemic attack. Blood pressure remains poorly controlled in a large proportion of patients after transient ischemic attack and under-treatment and poor adherence are important factors. Chronotherapy for blood pressure may result in more effective blood pressure control. More research is needed in this area. Hypertension is strongly associated with transient ischemic attack. Diurnal blood pressure patterns may influence subsequent stroke risk after transient ischemic attack and more evidence is needed to inform clinical practice to improve blood pressure management for transient ischemic attack patients.

Penumbral mismatch is underestimated using standard volumetric methods and this is exacerbated with time

BACKGROUND AND AIMS

The mismatch between perfusion weighted images (PWI) and diffusion weighted images (DWI) using MR is increasingly being applied in patient selection for therapeutic trials. Two approaches to the calculation of the mismatch volume exist--the commonly used volumetric and the more precise co-registration method, the latter of which considers lesion topography. That there are differences in the mismatch volume analysed by each method and that these are time dependent was hypothesised.

METHODS

Patients within 48 h of ischaemic stroke onset had baseline MR PWI/DWI mismatch and T2 outcome volumes at 3 months. Volumetric mismatch volume was defined as PWI minus DWI lesion. Co-registration mismatch volume was defined as the PWI defect lesion not overlapped by the co-registered DWI lesion.

RESULTS

72 patients of median age 74.0 years were studied. Median baseline MR was at 5.9 h (IQR 3.0, 20.4 h) after stroke onset. Consistent underestimation of the mismatch volume occurred using the volumetric method (volumetric median 9.3 ml, IQR 0, 63 ml; co-registration median 20.1 ml, IQR 3.2, 69.8 ml; p<0.0001). This difference increased with time from stroke onset (p = 0.006).

CONCLUSIONS

Volumetric analysis consistently underestimates the PWI/DWI mismatch volume compared with the more precise co-registration method. This effect increases with time.

A double-blind, placebo-controlled, randomized, multicenter study to investigate CHInese Medicine Neuroaid Efficacy on Stroke recovery (CHIMES Study)

Rationale Traditional Chinese Medications(TCM) have been reported to have beneficial effects in stroke patients, but were not rigorously evaluated by GCP standards. Aim This study tests the hypothesis that Neuroaid, a TCM widely used in China post-stroke, is superior to placebo in reducing neurological deficit and improving functional outcome in patients with acute cerebral infarction of an intermediate severity. Design This is a multicenter, randomised, double-blind, placebo-controlled study of Neuroaid in ischemic stroke patients with National Institute of Health Stroke Scale(NIHSS) 6-14 treated within 48 h of stroke onset. Neuroaid or placebo is taken (4 capsules) 3 times daily for 3 months. Treatments are assigned using block randomization, stratified for centers, via a central web-randomization system. With a power of 90% and two-sided test of 5% type I error, a sample size is 874. Allowing for a drop-out rate of up to 20%, 1100 individuals should be enrolled in this study. Study Outcomes The primary efficacy endpoint is the modified Rankin Scale(mRS) grades at 3 months. Secondary efficacy endpoints are the NIHSS score at 3 months; difference of NIHSS scores between baseline and 10 days, and between baseline and 3 months; difference of NIHSS sub-scores between baseline and 10 days, and between baseline and 3 months; mRS at 10 days, 1 month, and 3 months; Barthel index at 3 months; Mini Mental State Examination at 10 days and 3 months. Safety outcomes include complete blood count, renal and liver panels, and electrocardiogram.

STUDY REGISTRATION

ClinicalTrials.gov identifier: NCT00554723.

Classification of stroke subtypes

This article reviews published stroke subtype classification systems and offers rules and a basis for a new way to subtype stroke patients. Stroke subtyping can have different purposes, e.g. describing patients' characteristics in a clinical trial, grouping patients in an epidemiological study, careful phenotyping of patients in a genetic study, and classifying patients for therapeutic decision-making in daily practice. The classification should distinguish between ischemic and hemorrhagic stroke, subarachnoid hemorrhage, cerebral venous thrombosis, and spinal cord stroke. Regarding the 4 main categories of etiologies of ischemic stroke (i.e. atherothrombotic, small vessel disease, cardioembolic, and other causes), the classification should reflect the most likely etiology without neglecting the vascular conditions that are also found (e.g. evidence of small vessel disease in the presence of severe large vessel obstructions). Phenotypes of large cohorts can also be characterized by surrogate markers or intermediate phenotypes (e.g. presence of internal carotid artery plaque, intima-media thickness of the common carotid artery, leukoaraiosis, microbleeds, or multiple lacunae). Parallel classifications (i.e. surrogate markers) may serve as within-study abnormalities to support research findings.

New approach to stroke subtyping: the A-S-C-O (phenotypic) classification of stroke

We now propose a new approach to stroke subtyping. The concept is to introduce a complete 'stroke phenotyping' classification (i.e. stroke etiology and the presence of all underlying diseases, divided by grade of severity) as distinguished from past classifications that subtype strokes by characterizing only the most likely cause(s) of stroke. In this phenotype-based classification, every patient is characterized by A-S-C-O: A for atherosclerosis, S for small vessel disease, C for cardiac source, O for other cause. Each of the 4 phenotypes is graded 1, 2, or 3. One for 'definitely a potential cause of the index stroke', 2 for 'causality uncertain', 3 for 'unlikely a direct cause of the index stroke (but disease is present)'. When the disease is completely absent, the grade is 0; when grading is not possible due to insufficient work-up, the grade is 9. For example, a patient with a 70% ipsilateral symptomatic stenosis, leukoaraiosis, atrial fibrillation, and platelet count of 700,000/mm(3) would be classified as A1-S3-C1-O3. The same patient with a 70% ipsilateral stenosis, no brain imaging, normal ECG, and normal cardiac imaging would be identified as A1-S9-C0-O3. By introducing the 'level of diagnostic evidence', this classification recognizes the completeness, the quality, and the timing of the evaluation to grade the underlying diseases. Diagnostic evidence is graded in levels A, B, or C: A for direct demonstration by gold-standard diagnostic tests or criteria, B for indirect evidence or less sensitive or specific tests or criteria, and C for weak evidence in the absence of specific tests or criteria. With this new way of classifying patients, no information is neglected when the diagnosis is made, treatment can be adapted to the observed phenotypes and the most likely etiology (e.g. grade 1 in 1 of the 4 A-S-C-O phenotypes), and analyses in clinical research can be based on 1 of the 4 phenotypes (e.g. for genetic analysis purpose), while clinical trials can focus on 1 or several of these 4 phenotypes (e.g. focus on patients A1-A2-A3).

Improvements in the quality of care and health outcomes with new stroke care units following implementation of a clinician-led, health system redesign programme in New South Wales, Australia

BACKGROUND AND OBJECTIVES

Provision of evidence-based hospital stroke care is limited worldwide. In Australia, about a fifth of public hospitals provide stroke care units (SCUs). In 2001, the New South Wales (NSW) state government funded a clinician-led, health system redesign programme that included inpatient stroke services. Our objective was to determine the effects of this initiative for improving: (i) access to SCUs and care quality and (ii) health outcomes.

DESIGN, SETTING AND PARTICIPANTS

Preintervention-postintervention design (12 months prior and a minimum 6-12 months following SCU implementation). Retrospective, public hospital audit of 50 consecutive medical records per time period of stroke admissions (using International Classification of Diseases (ICD)-10 codes). Combined analyses for 15 hospitals presented.

OUTCOMES

Process of care indicators and patient independence (proportional odds modelling using modified Rankin scale).

RESULTS

Pre-programme cases (n = 703) (mean (SD) age 74 (14) years; female: 51%) and post-programme cases (n = 884) (mean age 74 (14) years; female: 49%) were comparable. Significant post-programme improvements for most process indicators were found, such as more brain imaging within 24 hours. Post-programme, access to SCUs increased 22-fold (95% CI 16.8 to 28.3). Improvement in inpatient independence at post-programme discharge was significant compared with pre-programme outcomes (proportional odds ratio 0.73, 95% CI 0.57 to 0.94; p = 0.013) when adjusted for patient clustering and case mix.

CONCLUSIONS

This distinctive SCU initiative was shown as effective for improving clinical practice and significantly reducing disability following stroke.

Imaging the penumbra - strategies to detect tissue at risk after ischemic stroke

The aim of thrombolytic therapy after acute ischemic stroke is salvage of the ischemic penumbra. Several imaging techniques have been used to identify the penumbra in patients who may benefit from reperfusion beyond the currently narrow 3-hour time-window for thrombolysis. We discuss the advantages and disadvantages of positron emission tomography (PET), single photon emission computed tomography (SPECT), MRI and CT scans. We comment on concepts of clinical-imaging mismatch models and we explore the implications for clinical trials.

Extensive hemispheric cerebral infarction

BACKGROUND AND PURPOSE

Patients with extensive hemispheric cerebral infarction have a high incidence of mortality and serious morbidity. Because of their poor prognosis, they warrant attention; however, in acute stroke therapy trials they do not appear to benefit from treatment. We sought to determine the clinical features, pathophysiological mechanisms, and outcome in a series of cases with radiologically defined extensive hemispheric infarction.

METHODS

Cases of extensive hemispheric infarction were ascretained retrospectively from stroke admissions during a 5-year period. Extensive hemispheric infarction was defined radiologically as infarction involving greater than 75% of the middle cerebral artery territory, with or without involvement of the adjacent anterior or posterior cerebral artery territories. Clinical, risk factor, and stroke mechanism data were compared with that of a control group of ischemic stroke patients admitted during the same period.

RESULTS

Extensive hemispheric infarction occurred in 53 of 1,440 cases of ischemic stroke (3.7%). Infarction involved the middle cerebral artery territory alone in 79% of cases, and the adjacent anterior or posterior cerebral artery territories as well as 21% of cases. A cardioembolic mechanism was likely in 58% of cases; 42% had atrial fibrillation. When compared with the control group, a cardioembolic mechanism was the only feature more frequently associated with extensive hemispheric infarction. The overall in-hospital mortality rate was 52%; 84% of those discharged from hospital required nursing home care because of severe disability.

CONCLUSION

Although uncommon, extensive hemispheric infarction is an important stroke subtype with dramatic and easily recognizable presenting clinical features, frequent cardio-embolic mechanism, an extremely poor outcome, and failure to benefit from most experimental acute stroke therapies.

Timing of clinically significant microembolism after carotid endarterectomy

PURPOSE

Post-operatively detected transcranial Doppler (TCD) embolic signals (ES) are associated with an increased risk of carotid endarterectomy (CEA) stroke/TIA. The aims here were to quantify this risk and determine the most efficient monitoring protocol.

METHODS

Sequential patients undergoing CEA (enrolled in a randomised, blinded, placebo-controlled trial of peri-operative dextran therapy) had 30-min TCD monitoring in the first post-operative hour. 30-min monitoring was also performed 2-3, 4-6 and 24-36 h post-operatively. First post-operative hour ES counts were correlated with peri-operative ipsilateral carotid stroke/TIA to determine the size of a clinically significant ES load and the magnitude of the associated risk. The exact Cochran-Armitage test for trend in proportions was used to determine when a clinically significant ES load was first detected.

RESULTS

141 patients (mean age 69.3 years, 72% male) were monitored during the first post-operative hour. An ES count >10 per recording was identified as the best overall predictor of ipsilateral stroke/TIA (sensitivity 72%, specificity 89%). 3/119 (2.5%) patients with 0-10 ES had ipsilateral carotid events compared to 8/22 (36.4%) patients with 11-115 ES (OR = 22.1, 95% CI 4.5, 138.4, p < 0.0001). 13/18 (72%) of subjects with >10 ES were identified in the first post-operative hour with no significant increase in the number of new cases over the subsequent 24-36 post-operative h (p = 0.354).

CONCLUSION

Patients with clinically significant post-operative microembolism had an approximately 15 times higher risk of ipsilateral stroke/TIA and most were identified during a 30-min study in the first post-operative hour.

Access to stroke care units in Australian public hospitals: facts and temporal progress

BACKGROUND

There is level I evidence that management of stroke patients in stroke units (SU) improves outcomes (death and institutionalization) by approximately 20%. In Australia, there is uncertainty as to the proportion of incident cases that have access to SU. Recent national and State-based policy initiatives to increase access to SU have been taken. However, objective evidence related to SU implementation progress is lacking. The aims of the study were (i) to determine the number of SU in Australian acute public hospitals in 2004, (ii) to describe hospitals according to national SU policy criteria and (iii) to compare results to the 1999 survey to track progress.

METHODS

The method used in the study was a cross-sectional, postal survey technique. The participants were clinical representatives considered appropriate to describe stroke care within survey hospitals.

RESULTS

The outcome of the study was presence of a SU according to an accepted definition. Response rate was 261/301 (87%). Sixty-one sites (23%) had either a SU and/or a dedicated stroke team. Fifty sites claimed to have a SU (19%). New South Wales with 23 had the most number of SU. Based on policy criteria, up to 64 sites could have a SU. In 1999, there were 35 public hospitals with a SU.

CONCLUSION

Access to SU in Australian public hospitals remains low compared with other countries (Sweden, 70%). Implementation strategies supported by appropriate health policy to improve access are needed.

Carotid endarterectomy for asymptomatic carotid stenosis

BACKGROUND

Carotid endarterectomy (CEA) is of proven benefit in recently-symptomatic patients with severe carotid stenosis. Its role in asymptomatic stenosis is still debated. The Asymptomatic Carotid Surgery Trial (ACST) more than doubled the number of patients randomised to CEA trials. This revised review incorporates the recently published ACST results.

OBJECTIVES

Our objective was to determine the effects of CEA for patients with asymptomatic carotid stenosis.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (searched May 2004), MEDLINE (1966 to May 2004), EMBASE (1980 to June 2004), Current Contents (1995 to January 1997), and reference lists of relevant articles. We contacted researchers in the field to identify additional published and unpublished studies.

SELECTION CRITERIA

All completed randomised trials comparing CEA to medical treatment in patients with asymptomatic carotid stenosis.

DATA COLLECTION AND ANALYSIS

Two reviewers extracted data and assessed trial quality. Attempts were made to contact investigators to obtain missing information.

MAIN RESULTS

Three trials with a total of 5223 patients were included. In these trials, the overall net excess of operation-related perioperative stroke or death was 2.9%. For the primary outcome of perioperative stroke or death or any subsequent stroke, patients undergoing CEA fared better than those treated medically (relative risk (RR) 0.69, 95% confidence interval (CI) 0.57 to 0.83). Similarly, for the outcome of perioperative stroke or death or subsequent ipsilateral stroke, there was benefit for the surgical group (RR 0.71, 95% CI 0.55 to 0.90). For the outcome of any stroke or death, there was a non-significant trend towards fewer events in the surgical group (RR 0.92, 95% CI 0.83 to 1.02). Subgroup analyses were performed for the outcome of perioperative stroke or death or subsequent carotid stroke. CEA appeared more beneficial in men than in women and more beneficial in younger patients than in older patients although the data for age effect were inconclusive. There was no statistically significant difference between the treatment effect estimates in patients with different grades of stenosis but the data were insufficient.

AUTHORS' CONCLUSIONS

Despite about a 3% perioperative stroke or death rate, CEA for asymptomatic carotid stenosis reduces the risk of ipsilateral stroke, and any stroke, by approximately 30% over three years. However, the absolute risk reduction is small (approximately 1% per annum over the first few years of follow up in the two largest and most recent trials) but it could be higher with longer follow up.

Results of a Multicentre, Randomised Controlled Trial of Intra-Arterial Urokinase in the Treatment of Acute Posterior Circulation Ischaemic Stroke

BACKGROUND

Patients with ischaemic stroke due to occlusion of the basilar or vertebral arteries may develop a rapid deterioration in neurological status leading to coma and often to death. While intra-arterial thrombolysis may be used in this context, no randomised controlled data exist to support its safety or efficacy.

METHODS

Randomised controlled trial of intra-arterial urokinase within 24 h of symptom onset in patients with stroke and angiographic evidence of posterior circulation vascular occlusion.

RESULTS

Sixteen patients were randomised, and there was some imbalance between groups, with more severe strokes occurring in the treatment arm. A good outcome was observed in 4 of 8 patients who received intra-arterial urokinase compared with 1 of 8 patients in the control group.

CONCLUSIONS

These results support the need for a large-scale study to establish the efficacy of intra-arterial thrombolysis for acute basilar artery occlusion.

Progressive dementia after first-ever stroke: a community-based follow-up study

OBJECTIVES

To examine the risk and determinants of a progressive dementia syndrome and cognitive impairment not dementia (CIND) in community-based nonaphasic first-ever stroke cases 1 year after stroke, relative to a matched community-based stroke-free group.

METHODS

Matched cohort design, with cognitive tests given on two occasions 9 months apart to 99 mild-to-moderate first-ever stroke patients and 99 age- and sex-matched people without stroke. At follow-up, progressive dementia or CIND were diagnosed, with judges blinded to stroke/nonstroke status.

RESULTS

Progressive dementia was diagnosed in 12.5% of stroke patients and 15.4% of those without strokes (RR 1.1, 95% CI 0.5 to 2.2, p = 0.85). CIND was diagnosed in 37.5% of stroke patients and 17.6% of participants without strokes (RR 2.1, 95% CI 1.2 to 3.4, p = 0.003). In multivariable regression, age (p = 0.04) and baseline cognition (p < 0.001) were independently associated with dementia whereas stroke (p = 0.002), age (p = 0.05), baseline cognition (p = 0.001), and baseline mood (p = 0.03) were independently associated with CIND at follow-up.

CONCLUSIONS

In this community-based nonaphasic sample, mild-to moderate first-ever stroke was not associated with the presence of progressive dementia 1 year later, but was clearly associated with a greater risk of cognitive impairment not dementia (CIND). Baseline mood impairment remained independently associated with CIND at 1 year after taking into account stroke, age, and baseline cognitive ability.

An unusual disease presenting at an unusual age: Susac’s syndrome

Susac's syndrome is a rare disease of unknown aetiology affecting the small vessels of the retina, brain, and cochlea. We present the case of a 55-year-old female, the oldest patient yet described with the condition, and highlight the syndrome's clinical features.

Neurological manifestations of cardiac myxoma: a review of the literature and report of cases

BACKGROUND AND AIMS

Cardiac myxoma is a rare but important cause of stroke, which affects young people. More recently the diagnosis has been enhanced by the use of echocardiograms. We aimed to review the neurological presentations, including stroke, of cardiac myxoma in this modern era of diagnosis and management.

METHODS

Records of patients with neurological presentations at the Austin and Repatriation Medical Centre and The Northern Hospital were retrieved from 1985 to late 2001, using International Classification of Diseases codes for atrial myxoma. Published literature reports were obtained by using Medline search database. An iterative process of bibliography review was utilised to identify reports not found by primary search. Case demographics, neurological presentations, investigations, treatment and outcome were recorded.

RESULTS

From the Austin and Repatriation Medical Centre and The Northern Hospital, 6 cases were reported in detail and 107 cases from the published literature were analysed. The mean age of all cases was 43 (range 6-82). There was a female to male predominance (3:2). While there were overlapping neurological presentations, the most common presentation was ischaemic stroke (83% of all patients) most often in multiple sites (41%). The other presentations included syncope (28%), psychiatric presentations (23%), headache (15%) and seizures (12%). Commonest means of reaching the diagnosis was by echocardiography. The myxoma was surgically resected in 69% of cases. Of all cases, 24% were autopsy reports, almost all prior to availability of echocardiograms (in mid-1970s).

CONCLUSIONS

Patients who presented with neurological complications of cardiac myxoma were young and stroke was by far the most common single presentation. Importantly, when all clinical manifestations were considered, almost half were potentially reversible. In recent years, echocardiography has made significant contribution to establishing the diagnosis less invasively. There is uncertainty about the role of anticoagulants. The treatment of choice remains surgical excision, although the timing post stroke is debatable. There is a need for large scale collaborative studies to help refine management strategies.

Hypoxic tissue in ischaemic stroke: persistence and clinical consequences of spontaneous survival

In ischaemic stroke, expansion of the infarct core occurs at the expense of surrounding hypoxic, metabolically compromised tissue over a period of 24 h or more in a considerable proportion of patients. It is uncertain whether hypoxic tissue observed at later times after stroke onset retains the potential for survival or whether such survival has an impact on functional outcome. These factors may determine the effectiveness of therapeutic strategies aimed at salvaging this tissue. We tested the hypotheses that metabolically compromised hypoxic tissue observed within 48 h after onset of ischaemic stroke retains the potential for spontaneous survival and that the impact of such survival on functional outcome is time dependent. Consecutive patients presenting within 48 h of ischaemic stroke were studied with [(18)F]fluoromisonidazole, a ligand binding to hypoxic but viable tissue, and PET. Subjects were grouped into two time epochs, </=12 and >12 h, based on the interval from stroke onset to the time of tracer injection, and had infarct volumes measured on CT/MRI at 7 days (n = 60). The total ischaemic volume (TIV) and the proportion of the TIV that spontaneously survived (surviving hypoxic volume ratio, SHVR) were defined from the co-registered CT/MRI images. These volumetric measures were correlated with neurological outcome assessed at day 7-10 by percentage change in the National Institutes of Health Stroke Scale (DeltaNIHSS), and at 3 months by Barthel Index (BI) and modified Rankin Score (mRS). Of 66 patients investigated, hypoxic tissue occurred in 33 and outcome data was available in 27. Hypoxic tissue constituted >20% of the TIV in 60% of studies </=12 h and 16% >12 h. The spontaneously surviving proportion of the TIV (median 6.9%) or hypoxic tissue (median 45.9%) was not significantly different in patient subgroups studied </=12 or >12 h after stroke onset. Spontaneous survival of hypoxic tissue (surviving hypoxic volume ratio) was associated with improved neurological outcome in both time epochs: </=12 h, DeltaNIHSS (r = 0.85, P < 0.01), day 90 BI (r = 0.86, P < 0.01) and day 90 mRS (r = -0.89, P < 0.01); >12 h, DeltaNIHSS (r = 0.59, P < 0.01) and day 90 mRS (r = -0.46, P < 0.05). The finding that similar proportions of hypoxic tissue survived spontaneously within each time epoch suggests that its fate is not predetermined. The favourable neurological outcome associated with spontaneous survival of hypoxic tissue, even 12-48 h after stroke onset, suggests that the volume of hypoxic tissue that progressed to infarction may represent a valuable target for therapeutic intervention.

Topography and Temporal Evolution of Hypoxic Viable Tissue Identified by 18 F-Fluoromisonidazole Positron Emission Tomography in Humans After Ischemic Stroke

Background and Purpose— We sought to characterize the spatial and temporal evolution of human cerebral infarction. Using a novel method of quantitatively mapping the distribution of hypoxic viable tissue identified by 18 F-fluoromisonidazole ( 18 F-FMISO) PET relative to the final infarct, we determined its evolution and spatial topography in human stroke.

Methods— Patients with acute middle cerebral artery territory stroke were imaged with 18 F-FMISO PET (n=19; <6 hours, 4; 6 to 16 hours, 4; 16 to 24 hours, 5; 24 to 48 hours, 6). The hypoxic volume (HV) comprised voxels with significant ( P <0.05; >1 mL) uptake on statistical parametric mapping compared with 15 age-matched controls. Central, peripheral, and external zones of the corresponding infarct on the anatomically coregistered delayed CT were defined according to voxel distance from the infarct center and subdivided into 24 regions by coronal, sagittal, and axial planes. Maps (“penumbragrams”) displaying the percentage of HV in each region were generated for each time epoch.

Results— Higher HV was observed in the central region of the infarct in patients studied within 6 hours of onset (analysis of covariance [ANCOVA]; P <0.05) compared with those studied later, in whom the HV was mainly in the periphery or external to the infarct. HV was maximal in the superior, mesial, and posterior regions of the infarct (ANCOVA; P <0.05).

Conclusions— These observations suggest that infarct expansion occurs at the expense of hypoxic tissue from the center to the periphery of the ischemic region in humans, similar to that seen in experimental animal models. These findings have important pathophysiological and therapeutic implications.

Macrophages and Microglia Produce Local Trophic Gradients That Stimulate Axonal Sprouting Toward but Not beyond the Wound Edge

Following injury to the mammalian CNS, axons sprout in the vicinity of the wound margin. Growth then ceases and axons fail to cross the lesion site. In this study, using dopaminergic sprouting in the injured striatum as a model system, we have examined the relationship of periwound sprouting fibers to reactive glia and macrophages. In the first week after injury we find that sprouting fibers form intimate relationships with activated microglia as they traverse toward the wound edge. Once at the wound edge, complicated plexuses of fibers form around individual macrophages. Axons, however, fail to grow further into the interior of the wound despite the presence of many macrophages in this location. We find that the expression of BDNF by activated microglia progressively increases as the wound edge is approached, while GDNF expression by macrophages is highest at the immediate wound margin. In contrast, the expression of both factors is substantially reduced within the macrophage-filled interior of the wound. Our data suggest that periwound sprouting fibers grow toward the wound margin along an increasing trophic gradient generated by progressively microglial and macrophage activation. Once at the wound edge, sprouting ceases over macrophages at the point of maximal neurotrophic factor expression and further axonal growth into the relatively poor trophic environment of the wound core fails to occur.

Reemergence of activation with poststroke somatosensory recovery: a serial fMRI case study

The authors demonstrate the potential for poststroke return of activation in regions normally involved in touch discrimination in a serial, whole-brain fMRI study of a patient with marked sensory loss followed by good recovery. A return of activation in ipsilesional primary and bilateral secondary somatosensory cortices was observed at 3 months after stroke and was maintained at 6 months, indicating a reemergence of activation after the interval of somatosensory recovery. There was little evidence of neural plastic changes early after stroke (2 weeks), when sensory loss was severe.

Baseline blood pressure but not early computed tomography changes predicts major hemorrhage after streptokinase in acute ischemic stroke

BACKGROUND AND PURPOSE

Intracerebral hemorrhage is the most serious complication of thrombolytic therapy for stroke. We explored factors associated with this complication in the Australian Streptokinase Trial.

METHODS

The initial CT scans (< or =4 hours after stroke) of 270 patients were reviewed retrospectively by an expert panel for early signs of ischemia and classified into the following 3 categories: no signs or < or =1/3 or >1/3 of the vascular territory. Hemorrhage on late CT scans was categorized as major or minor on the basis of location and mass effect. Stepwise, backward elimination, multivariate logistic regression analysis was used to identify risk factors for each hemorrhage category.

RESULTS

Major hemorrhage occurred in 21% of streptokinase (SK) and 4% of placebo patients. Predictors of major hemorrhage were SK treatment (odds ratio [OR], 6.40; 95% CI, 2.50 to 16.36) and elevated systolic blood pressure before therapy (OR, 1.03; 95% CI, 1.01 to 1.05). Baseline systolic blood pressure >165 mm Hg in SK-treated patients resulted in a >25% risk of major secondary hemorrhage. Early ischemic CT changes, either < or =1/3 or >1/3, were not associated with major hemorrhage (OR, 1.58; 95% CI, 0.65 to 3.83; and OR, 1.11; 95% CI, 0.45 to 2.76, respectively). Minor hemorrhage occurred in 30% of the SK and 26% of the placebo group. Predictors of minor hemorrhage were male sex, severe stroke, early CT changes, and SK treatment. Ninety-one percent of patients with major hemorrhage deteriorated clinically compared with 23% with minor hemorrhage.

CONCLUSIONS

SK increased the risk of both minor and major hemorrhage. Major hemorrhage was also more likely in patients with elevated baseline systolic blood pressure. However, early CT changes did not predict major hemorrhage. Results from this study highlight the importance of baseline systolic blood pressure as a potential cause of hemorrhage in patients undergoing thrombolysis.

Statistical parametric mapping of hypoxic tissue identified by [(18)F]fluoromisonidazole and positron emission tomography following acute ischemic stroke

Positron emission tomography (PET) and the ligand [(18)F]fluoromisonidazole ((18)F-FMISO) have been used to image hypoxic tissue in the brain following acute stroke. Existing region of interest (ROI)-based methods of analysis are time consuming and operator-dependent. We describe and validate a method of statistical parametric mapping to identify regions of increased (18)F-FMISO uptake. The (18)F-FMISO PET images were transformed into a standardized coordinate space and intensity normalized. Then t statistic maps were created using a pooled estimate of variance. Statistical inference was based on the theory of Gaussian Random Fields. We examined the homogeneity of variance in normal subjects and the influence of normalization by mean whole brain activity versus mean activity in the contralateral hemisphere. Validity of the distributional assumptions inherent in parametric analysis was tested by comparison with a non-parametric method. The results of parametric analysis were also compared with those obtained with the existing ROI-based method. Variance in uptake at each voxel in normal subjects was homogeneous and not affected by mean voxel activity or distance from the centre of the image. The method of normalization influenced results significantly. Normalization by whole brain mean activity resulted in a smaller volume of tissue being classified as hypoxic compared to normalisation by mean activity in the contralateral hemisphere. The ROI-based method was subject to interobserver variability with a coefficient of variability of 16%. The volumes of hypoxic tissue identified by parametric and nonparametric methods were highly correlated (r = 0.99). These findings suggest that using a pooled variance and contralateral hemisphere normalisation, statistical parametric mapping can be used to objectively identify regions of increased (18)F-FMISO uptake following acute stroke in individual subjects.

Informal care for stroke survivors: results from the North East Melbourne Stroke Incidence Study (NEMESIS)

BACKGROUND AND PURPOSE

Informal caregivers play an important role in the lives of stroke patients, but the cost of providing this care has not been estimated. The purpose of this study was to determine the nature and amount of informal care provided to stroke patients and to estimate the economic cost of that care.

METHODS

The primary caregivers of stroke patients registered in the North East Melbourne Stroke Incidence Study (NEMESIS) were interviewed at 3, 6, and 12 months after stroke, and the nature and amount of informal care provided were documented. The opportunity and replacement costs of informal care for all first-ever-in-a-lifetime strokes (excluding subarachnoid hemorrhages) that occurred in 1997 in Australia were estimated.

RESULTS

Among 3-month stroke survivors, 74% required assistance with activities of daily living and received informal care from family or friends. Two thirds of primary caregivers were women, and most primary caregivers (>90%) provided care during family or leisure time. Total first-year caregiver time costs for all first-ever-in-a-lifetime strokes were estimated to be A$21.7 million (opportunity cost approach) or A$42.5 million (replacement cost approach), and the present values of lifetime caregiver time costs were estimated to be A$171.4 million (opportunity cost approach) or A$331.8 million (replacement cost approach).

CONCLUSIONS

Informal care for stroke survivors represents a significant hidden cost to Australian society. Because our community is rapidly aging, this informal care burden may increase significantly in the future.

Periwound dopaminergic sprouting is dependent on numbers of wound macrophages

Injury to many regions of the central nervous system, including the striatum, results in a periwound or 'abortive' sprouting response. In order to directly evaluate whether macrophages play an important role in stimulating periwound sprouting, osteopetrotic (op/op) mice, which when young are deficient in a variety of macrophage subtypes, were given striatal wounds and the degree of dopaminergic sprouting subsequently assessed. Two weeks postinjury, significantly fewer wound macrophages were present in the striata of op/op mice compared with controls (144 +/- 30.1 in op/op mice vs. 416.6 +/- 82.3 in controls, P < 0.005, analysis performed on a section transecting the middle of the wound). Dopamine transporter immunohistochemistry revealed a marked decrease in the intensity of periwound sprouting in the op/op group of animals. Quantification of this effect using [H3]-mazindol autoradiography confirmed that periwound sprouting was reduced significantly in the op/op mice compared with controls (71.4 +/- 21.7 fmol/mg protein in op/op mice vs. 210.7 +/- 27.1 fmol/mg protein in controls, P < 0.0005). In the two groups of animals the magnitude of the sprouting response in individuals was closely correlated with the number of wound macrophages (R = 0.83, R2 = 0.69). Our findings provide strong support for the crucial involvement of macrophages in inducing dopaminergic sprouting after striatal injury.

Lacunar stroke: transoesophageal echocardiographic factors influencing long-term prognosis

OBJECTIVE

Since little is known concerning factors which may influence long-term prognosis of patients presenting with lacunar stroke, we conducted a longitudinal study of this stroke subtype. Variables likely to affect outcome were assessed at baseline, including those from transoesophageal echocardiographic studies.

METHODS

Consecutive patients presenting with first-ever lacunar stroke underwent diagnostic workup that included brain CT or MRI, carotid duplex, and transthoracic and transoesophageal echocardiography. An assessment of patients was planned at entry (baseline), and thereafter every 12 months (clinic visit or telephone call), drop-out, or endpoint. The primary endpoint was nonfatal or fatal stroke. Secondary endpoint was death due to any cause.

RESULTS

Among 60 consecutive lacunar patients with the mean follow-up period of 3.9 years, 12 patients (20%) had stroke recurrence. The mean annual rate for stroke was 5.2%, and for death 2.8%. For multivariate Cox proportional hazards analysis, the following three variables with the values of p < 0.1 after univariate testing were chosen: age (p = 0.095); aortic atheroma (p = 0.066); and any source of embolism from heart (p = 0.007). Any source of embolism from heart was the only factor which significantly enhanced the risk of stroke recurrence (p = 0.015). Using Kaplan-Meier life table analysis, the curves of percent free of recurrent stroke were significantly different (log rank test p = 0.002).

CONCLUSIONS

Until the mechanism of lacunar stroke is better understood, it is reasonable to suggest that its investigation and prevention should be directed at all potential causes of future strokes including cardioembolism.

Cost of stroke in Australia from a societal perspective: results from the North East Melbourne Stroke Incidence Study (NEMESIS)

BACKGROUND AND PURPOSE

Accurate information about resource use and costs of stroke is necessary for informed health service planning. The purpose of this study was to determine the patterns of resource use among stroke patients and to estimate the total costs (direct service use and indirect production losses) of stroke (excluding SAH) in Australia for 1997.

METHODS

An incidence-based cost-of-illness model was developed, incorporating data obtained from the North East Melbourne Stroke Incidence Study (NEMESIS). The costs of stroke during the first year after stroke and the present value of total lifetime costs of stroke were estimated.

RESULTS

The total first-year costs of all first-ever-in-a lifetime strokes (SAH excluded) that occurred in Australia during 1997 were estimated to be A$555 million (US$420 million), and the present value of lifetime costs was estimated to be A$1.3 billion (US$985 million). The average cost per case during the first 12 months and over a lifetime was A$18 956 (US$14 361) and A$44 428 (US$33 658), respectively. The most important categories of cost during the first year were acute hospitalization (A$154 million), inpatient rehabilitation (A$150 million), and nursing home care (A$63 million). The present value of lifetime indirect costs was estimated to be A$34 million.

CONCLUSIONS

Similar to other studies, hospital and nursing home costs contributed most to the total cost of stroke (excluding SAH) in Australia. Inpatient rehabilitation accounts for approximately 27% of total first-year costs. Given the magnitude of these costs, investigation of the cost-effectiveness of rehabilitation services should become a priority in this community.

Dextran reduces embolic signals after carotid endarterectomy

One hundred fifty patients undergoing carotid endarterectomy were randomly assigned to receive intravenous 10% dextran 40 or placebo. Transcranial Doppler monitoring of the ipsilateral middle cerebral artery 0 to 1 hour postoperatively detected embolic signals in 57% of placebo and 42% of dextran patients, with overall embolic signal counts 46% less for dextran (p = 0.052). Two to 3 hours postoperatively, embolic signals were present in 45% of placebo and 27% of dextran patients, with embolic signal counts 64% less for dextran (p = 0.040). We conclude that dextran reduces embolic signals within 3 hours of CEA.

Incidence of the major stroke subtypes: initial findings from the North East Melbourne stroke incidence study (NEMESIS)

BACKGROUND AND PURPOSE

Population-based stroke incidence studies are the only accurate way to determine the number of strokes that occur in a given society. Because the major stroke subtypes have different patterns of incidence and outcome, information on the natural history of stroke subtypes is essential. The purpose of the present study was to determine the incidence and case-fatality rate of the major stroke subtypes in a geographically defined region of Melbourne, Australia.

METHODS

All suspected strokes that occurred among 133 816 residents of suburbs north and east of Melbourne, Australia, during a 12-month period of 1996 and 1997 were identified and assessed. Multiple overlapping sources were used to ascertain cases, and standard criteria for stroke and case-fatality were used. Stroke subtypes were defined by CT, MRI, and autopsy.

RESULTS

Three hundred eighty-one strokes occurred among 353 persons during the study period, with 276 (72%) being first-ever-in-a-lifetime strokes. Of these, 72.5% (95% CI 67.2% to 77.7%) were cerebral infarction, 14.5% (95% CI 10.3% to 18.6%) were intracerebral hemorrhage, 4.3% (95% CI 1.9% to 6.8%) were subarachnoid hemorrhage, and 8.7% (95% CI 5.4% to 12.0%) were stroke of undetermined type. The 28-day case-fatality rate was 12% (95% CI 7% to 16%) for cerebral infarction, 45% (95% CI 30% to 60%) for intracerebral hemorrhage, 50% (95% CI 22% to 78%) for subarachnoid hemorrhage, and 38% (95% CI 18% to 57%) for stroke of undetermined type.

CONCLUSIONS

The overall distribution of stroke subtypes and 28-day case-fatality rates are not significantly different from those of most European countries or the United States. There may, however, be some differences in the incidence of subtypes within Australia.

Prediction of the final infarct volume within 6 h of stroke using single photon emission computed tomography with technetium-99m hexamethylpropylene amine oxime

BACKGROUND

A simple method to predict the final infarct volume within 6 h of onset of hemispheric ischemic stroke based on the measurement of cerebral blood flow (CBF) using single photon emission computed tomography (SPECT) with techneticum-99m hexamethylpropylene amine oxime ((99m)Tc-HMPAO) was investigated in a clinical model involving patients without definite early reperfusion or clinical recovery.

METHODS

A group of 16 patients (group 1) was used to establish the methodology, which was then validated in a second group of 14 patients (group 2). The final infarct volume was defined using computed tomography (CT) performed at least 7 days after stroke. The relative CBF threshold value, expressed as a percentage of the mean contralateral hemispheric value, which most closely estimated the final infarct size on coregistered CT was established for each patient.

RESULTS

The mean threshold CBF value for group 1 was 63.7%. When this value was used to predict infarct size in group 2, a close correlation was observed between the actual and the estimated sizes (r = 0.973, p < 0.0001). This value was not time dependent.

CONCLUSIONS

If no significant early reperfusion or clinical recovery occurs, a CBF threshold value of 63.7% on (99m)Tc-HMPAO SPECT performed within 6 h of stroke onset will reliably predict the final infarct size.

Newer antiplatelet therapies in stroke prevention

BACKGROUND

Aspirin has been the mainstay of antiplatelet therapy in stroke prevention for 30 years. In the past decade, a number of new antiplatelet strategies have been shown in clinical trials to provide some benefits over aspirin therapy. These new compounds include ticlopidine, clopidogrel and the combination of aspirin with dipyridamole.

OBJECTIVES

To review the efficacy and dosage of aspirin in stroke prevention, and to review the benefits and risks of the newer strategies, compared with aspirin. Based on the evidence from randomised, controlled clinical trials and systematic overviews, to present practical clinical guidelines for the use of aspirin and the newer antiplatelet drugs.

DISCUSSION

For most patients aspirin monotherapy is still recommended as the first line antiplatelet strategy. However, some stroke clinicians are now recommending the combination of aspirin plus dipyridamole as a first line approach. For patients who are allergic to aspirin, clopidogrel is the drug of first choice and has largely replaced ticlopidine. For aspirin failures, either combined aspirin plus dipyridamole, or clopidogrel, are recommended. The combination of aspirin plus clopidogrel has theoretical appeal, is valuable in prevention of coronary stent thrombosis and is undergoing clinical trial in stroke prevention. Other novel approaches, such as oral platelet Gp IIb/IIIa antagonists are also being evaluated.

Reduced BDNF mRNA expression in the Parkinson's disease substantia nigra

Brain-derived neurotrophic factor (BDNF) has potent effects on survival and morphology of dopaminergic neurons and thus its loss could contribute to death of these cells in Parkinson's disease (PD). In situ hybridization revealed that BDNF mRNA is strongly expressed by dopaminergic neurons in control substantia nigra pars compacta (SNpc). In clinically and neuropathologically typical PD, SNpc BDNF mRNA expression is reduced by 70% (P = 0.001). This reduction is due, in part, to loss of dopaminergic neurons which express BDNF. However, surviving dopaminergic neurons in the PD SNpc also expressed less BDNF mRNA (20%, P = 0.02) than their normal counterparts. Moreover, while 15% of control neurons had BDNF mRNA expression >1 SD below the control mean, twice as many (28%) of the surviving PD SNpc dopaminergic neurons had BDNF mRNA expression below this value. This 13% difference in proportions (95% CI 8-17%, P < or = 0.000001) indicates the presence of a subset of neurons in PD with particularly low BDNF mRNA expression. Moreover, both control and PD neurons displayed a direct relationship between the density of BDNF mRNA expression per square micrometer of cell surface and neuronal size (r(2) = 0.93, P </= 0.00001) which was lost only in PD neurons expressing the lowest levels of BDNF mRNA. If BDNF is an autocrine/paracrine factor for SNpc dopaminergic neurons, loss of BDNF-expressing neurons may compromise the well-being of their surviving neighbors. Moreover, neurons expressing particularly low levels of BDNF mRNA may be those at greatest risk of injury in PD and possibly the trigger for the degeneration itself.

Inhibition of brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor expression reduces dopaminergic sprouting in the injured striatum

After striatal injury, sprouting dopaminergic fibres grow towards and intimately surround wound macrophages which, together with microglia, express the dopaminergic neurotrophic factors glial cell line-derived neurotrophic factor (GDNF) and brain derived neurotrophic factor (BDNF). To evaluate the importance of these endogenously secreted neurotrophic factors in generating striatal peri-wound dopaminergic sprouting, the peri-wound expression of BDNF or GDNF was inhibited by intrastriatal infusion of antisense oligonucleotides for 2 weeks in mice. Knock-down of both BDNF and GDNF mRNA and protein levels in the wounded striatum were confirmed by in situ hybridization and enzyme-linked immunosorbent assay, respectively. Dopamine transporter immunohisto-chemistry revealed that inhibition of either BDNF or GDNF expression resulted in a marked decrease in the intensity of peri-wound sprouting. Quantification of this effect using [H3]-mazindol autoradiography confirmed that peri-wound sprouting was significantly reduced in mice receiving BDNF or GDNF antisense infusions whilst control infusions of buffered saline or sense oligonucleotides resulted in the pronounced peri-wound sprouting response normally associated with striatal injury. BDNF and GDNF thus appear to be important neurotrophic factors inducing dopaminergic sprouting after striatal injury.

Stroke incidence on the east coast of Australia: the North East Melbourne Stroke Incidence Study (NEMESIS)

BACKGROUND AND PURPOSE

Community-based stroke incidence studies are the most accurate way of explaining mortality trends and developing public health policy. The purpose of this study was to determine the incidence of stroke in a geographically defined region of Melbourne, Australia.

METHODS

All suspected strokes occurring in a population of 133 816 residents in suburbs north and east of Melbourne, Australia, during a 12-month period of 1996 and 1997 were found and assessed. Multiple overlapping sources were used to ascertain cases, and standard definitions and criteria for stroke and case fatality were used.

RESULTS

A total of 381 strokes occurred among 353 people during the study period, 276 (72%) of which were first-ever-in-a-lifetime strokes. The crude annual incidence rate (first-ever strokes) was 206 (95% CI, 182 to 231) per 100 000 per year overall, 195 (95% CI, 161 to 229) for males, and 217 (95% CI, 182 to 252) for females. The corresponding rates adjusted to the "world" population were 100 (95% CI, 80 to 119) overall, 113 (95% CI, 92 to 134) for males, and 89 (95% CI, 70 to 107) for females. The 28-day case fatality rate for first-ever strokes was 20% (95% CI, 16% to 25%).

CONCLUSIONS

The incidence rate of stroke in our population-based study is similar to that of many European studies but is significantly higher than that observed on the west coast of Australia.

The fate of hypoxic tissue on 18F-fluoromisonidazole positron emission tomography after ischemic stroke

We studied 24 patients up to 51 hours after ischemic stroke using 18F-fluoromisonidazole positron emission tomography to determine the fate of hypoxic tissue likely to represent the ischemic penumbra. Areas of hypoxic tissue were detected on positron emission tomography in 15 patients, and computed tomography was available in 12 patients, allowing comparison with the infarct volume to determine the proportions of the hypoxic tissue volume that infarcted and survived. The proportion of patients with hypoxic tissue and the amount of hypoxic tissue detected declined with time. On average, 45% of the total hypoxic tissue volume survived and 55% infarcted. Up to 68% (mean, 17.5%) of the infarct volume was initially hypoxic. Most of the tissue "initially affected" proceeded to infarction. We correlated hypoxic tissue volumes with neurological and functional outcome assessed using the National Institutes of Health Stroke Scale, Barthel Index, and Rankin Score. Initial stroke severity correlated significantly with the "initially affected" volume, neurological deterioration during the first week after stroke with the proportion of the "initially affected" volume that infarcted, and functional outcome with the infarct volume. Significant reductions in the size of the infarct and improved clinical outcomes might be achieved if hypoxic tissue can be rescued.

New dopaminergic neurons in Parkinson's disease striatum

A new population of dopaminergic neurons has been identified in Parkinson's disease striatum. These neurons are sufficiently numerous to have an important effect on dopaminergic function in the striatum.