The prognostic significance of changes in X-ray attenuation on CT in established cerebral infarcts

CT angiography and CT perfusion improve prediction of infarct volume in patients with anterior circulation stroke

Introduction

We investigated whether baseline CT angiography (CTA) and CT perfusion (CTP) in acute ischemic stroke could improve prediction of infarct presence and infarct volume on follow-up imaging.

Methods

We analyzed 906 patients with suspected anterior circulation stroke from the prospective multicenter Dutch acute stroke study (DUST). All patients underwent baseline non-contrast CT, CTA, and CTP and follow-up non-contrast CT/MRI after 3 days. Multivariable regression models were developed including patient characteristics and non-contrast CT, and subsequently, CTA and CTP measures were added. The increase in area under the curve (AUC) and R² was assessed to determine the additional value of CTA and CTP.

Results

At follow-up, 612 patients (67.5 %) had a detectable infarct on CT/MRI; median infarct volume was 14.8 mL (interquartile range (IQR) 2.8–69.6). Regarding infarct presence, the AUC of 0.82 (95 % confidence interval (CI) 0.79–0.85) for patient characteristics and non-contrast CT was improved with addition of CTA measures (AUC 0.85 (95 % CI 0.82–0.87); p < 0.001) and was even higher after addition of CTP measures (AUC 0.89 (95 % CI 0.87–0.91); p < 0.001) and combined CTA/CTP measures (AUC 0.89 (95 % CI 0.87–0.91); p < 0.001). For infarct volume, adding combined CTA/CTP measures (R² = 0.58) was superior to patient characteristics and non-contrast CT alone (R² = 0.44) and to addition of CTA alone (R² = 0.55) or CTP alone (R² = 0.54; all p < 0.001).

Conclusion

In the acute stage, CTA and CTP have additional value over patient characteristics and non-contrast CT for predicting infarct presence and infarct volume on follow-up imaging. These findings could be applied for patient selection in future trials on ischemic stroke treatment.

Electronic supplementary material

The online version of this article (doi:10.1007/s00234-015-1636-z) contains supplementary material, which is available to authorized users.

Brain CT and MRI: differential diagnosis of imaging findings

Following a traditional approach, in Chapters 5 and 14-29 in the previous volume, diverse brain diseases are listed and their imaging findings described in detail. In this chapter the approach is from the imaging finding to the disease: for instance, what list of diseases can give rise to a contrast-enhancing mass in the cerebellopontine angle? Imaging findings that are reviewed in succession include the location of the lesion, its multiplicity and symmetry, its volume, ranging from atrophy to mass effect, its homogeneity, its density, measurable by computed tomography (CT), its appearance on T1, T2, and diffusion magnetic resonance imaging (MRI), and, finally, its characteristics after the infusion of intravenous contrast. A differential diagnosis for each finding is provided. While the approach adopted in this chapter is unconventional, we hope that it will be most helpful to anyone reading images. Furthermore, it could serve as the basis to create or complete image databases to guide in the interpretation of brain CT and MRI.

CT volume/density ratio as the marker of ischaemic brain injury

OBJECTIVES

We believe that the CT volume/density ratio (VDR) of infarcted area reflects the degree of brain tissue damage during ischaemic stroke (IS).

PATIENTS AND METHODS

Forty six patients with IS were prospectively enrolled into the study. CT scan was performed on days 1 and 10 of hospitalization. S100BB serum level, gelatinase activities (MMP-2 and MMP-9) and neurological examination (NIHSS) were performed on days 1, 5 and 10 of IS. After 3 months, 42 patients were examined by functional disability scales: Barthel index (BI) and modified Rankin scale (mRS).

RESULTS

The VDR of ischaemic focus correlated well with the average S100BB serum level, MMP-9 serum activity and NIHSS score. The weak but statistically significant relationships were noticed between the VDR vs BI and mRS estimated 3 months after stroke.

CONCLUSION

VDR reflects well the damage ratio of brain tissue during IS. In addition, the study underlines the relationship between VDR vs patients' neurological status and disability after IS.

A systematic review of clinical trials of pharmacological interventions for acute ischaemic stroke (1955-2008) that were completed, but not published in full

BACKGROUND

We assessed the prevalence, and potential impact of, trials of pharmacological agents for acute stroke that were completed but not published in full. Failure to publish trial data is to be deprecated as it sets aside the altruism of participants' consent to be exposed to the risks of experimental interventions, potentially biases the assessment of the effects of therapies, and may lead to premature discontinuation of research into promising treatments.

METHODS

We searched the Cochrane Stroke Group's Specialised Register of Trials in June 2008 for completed trials of pharmacological interventions for acute ischaemic stroke, and searched MEDLINE and EMBASE (January 2007 - March 2009) for references to recent full publications. We assessed trial completion status from trial reports, online trials registers and correspondence with experts.

RESULTS

We identified 940 trials. Of these, 125 (19.6%, 95% confidence interval 16.5-22.6) were completed but not published in full by the point prevalence date. They included 16,058 participants (16 trials had over 300 participants each) and tested 89 different interventions. Twenty-two trials with a total of 4,251 participants reported the number of deaths. In these trials, 636/4251 (15.0%) died.

CONCLUSIONS

Our data suggest that, at the point prevalence date, a substantial body of evidence that was of relevance both to clinical practice in acute stroke and future research in the field was not published in full. Over 16,000 patients had given informed consent and were exposed to the risks of therapy. Responsibility for non-publication lies with investigators, but pharmaceutical companies, research ethics committees, journals and governments can all encourage the timely publication of trial data.

The Relationship Between Baseline Blood Pressure and Computed Tomography Findings in Acute Stroke

Background and Purpose— High blood pressure (BP) is present in ≈80% of patients with acute ischemic stroke and is independently associated with poor outcome. There are few data examining the relationship between admission BP and acute CT findings.

Methods— TAIST was a randomized controlled trial assessing 10 days of treatment with tinzaparin versus aspirin in 1489 patients with acute ischemic stroke (<48 hr) with admission BP of ≤220/120 mmHg. CT brain scans were performed before randomization and after 10 days. The relationships between baseline BP and adjudicated CT findings were assessed. Odds ratios per 10 mmHg change in BP were calculated.

Results— Higher systolic BP (SBP) was associated with abnormal CT scans because of independent associations with chronic changes of leukoariosis (OR, 1.12; 95% CI, 1.05–1.17) and old infarction (OR, 1.12; 95% CI, 1.06–1.17) at baseline, and signs of visible infarction at day 10 (OR, 1.06; 95% CI, 1.00–1.13). A lower SBP was associated with signs of acute infarction (OR, 0.94; 95% CI, 0.89–0.99). Hemorrhagic transformation, dense middle cerebral artery sign, mass effect, and cerebral edema at day 10 were not independently associated with baseline BP.

Conclusion— Although high baseline BP is independently associated with a poor outcome after stroke, this was not shown to be through an association with increased hemorrhagic transformation, cerebral edema, or mass effect; trial design may be suboptimal to detect this. Higher SBP is associated with visible infarction on day 10 scans. The influence of changing BP in acute stroke on CT findings is still to be ascertained.

Computed tomographic changes in lacunar syndromes

BACKGROUND

Lacunes are small deep infarcts due to occlusion of long-perforating arterial branches. The clinical presentation and outcome are variable. The present study investigates the prognostic value of comparing repeated computed tomographic (CT) scans in patients with a lacunar syndrome (LACS).

PATIENTS AND METHODS

From a series of 220 patients, subsequently admitted with a first-ever stroke, 32 were diagnosed as LACS. CT scans without contrast enhancement were performed on day 3 and 10 after onset of the symptoms. A lacune was considered as responsible for the LACS when its location corresponded to the expected cerebral hemisphere and when it changed in size and/or in X-ray attenuation on the CT scans from day 3 to 10. The size of the lacune was also measured and compared on both time points. The patients were divided into two groups according to the modified Rankin (R) scale at 3 months, in those who were independent (R 0-1-2) and in those who remained handicapped (R 3-4-5).

RESULTS

The patients who remained disabled at 3 months were older and more severely impaired on admission, and had more frequent cardiac problems and cognitive decline than the independent ones. On CT scans of the brain a higher incidence of leukoaraiosis was observed in this group. Only in three patients of each group no relevant lacune could be observed both on day 3 and 10. The average size of the symptomatic lacune on day 3 and 10 was not statistically different between both groups, when comparing all patients with a LACS. When comparing only those patients with a visible symptomatic lacunar infarct on one of the CT scans, however, the average size of the symptomatic deep infarct was smaller in the independent than the handicapped patients on day 3 as well as on day 10. The lacune decreased in average size from day 3 to 10 in the former group but remained unchanged in the group of disabled patients.

CONCLUSION

The outcome of patients with a LACS depends on several factors including age, cognitive and cardiac status, the presence of leukoaraiosis and also the size of the symptomatic lacune.

ASPECTS on CTA Source Images Versus Unenhanced CT

Background and Purpose— The Alberta Stroke Program Early CT Score (ASPECTS) is a grading system to assess ischemic changes on CT in acute ischemic stroke. CT angiography–source images (CTA-SI) predict final infarct volume. We examined whether the final infarct ASPECTS and clinical outcome were more related to acute CTA-SI ASPECTS than to the acute noncontrast CT (NCCT) ASPECTS.

Methods— ASPECTS was assigned by 2 raters on the acute NCCT, CTA-SI, and follow-up imaging. The mean baseline ASPECTS of acute NCCT and CTA-SI was compared with the follow-up ASPECTS. Rate ratios (RRs) were used to quantify the relationship between the dichotomized baseline ASPECTS (categorized as 0 to 7 versus 8 to 10) and favorable patient outcome.

Results— Thirty-nine patients were recruited. Proximal occlusion (internal carotid artery or middle cerebral artery) was seen in 62%, M2 occlusion in 18%, and no occlusion was seen in 20% of patients. The median time between symptom onset and imaging was 1.9 (1.2 to 2.5) hours. There was a significantly larger difference of 1.4 between the mean baseline NCCT and CTA-SI ASPECTS in patients who had more ischemic changes (follow-up ASPECTS=0 to 3) than a difference of 0.6 in patients who had near-to-normal CT scans (follow-up ASPECTS=8 to 10). The rate of favorable outcome for acute NCCT ASPECTS of 8 to 10 was 51.8% versus 25.0% for 0 to 7 (RR, 2.1, 95% CI: 0.7 to 5.9, P =0.12). For acute CTA-SI ASPECTS of 8 to 10, the rate of favorable outcome was 58.8% versus 31.8% for 0 to 7 (RR, 1.8, 95% CI: 0.9 to 3.8, P =0.09).

Conclusions— CTA-SI ASPECTS provides added information in the prediction of final infarct size.