Predictors of new remote cerebral microbleeds after IV thrombolysis for ischemic stroke

OBJECTIVE

To assess the frequency, associated factors, and underlying vasculopathy of new remote cerebral microbleeds (CMB), as well as the risk of concomitant hemorrhagic complications related to new CMBs, after IV thrombolysis (IVT) in acute stroke patients.

METHODS

We conducted an observational study using data from our local thrombolysis registry. We included consecutive stroke patients with MRI (3T)-based IVT and a follow-up MRI the next day between 2008 and 2017 (n = 396). Only CMBs located outside of the ischemic lesions were considered. We also performed a meta-analysis on new CMBs after IVT that included 2 additional studies.

RESULTS

In our cohort, new remote CMBs occurred in 16/396 patients (4.0%) after IVT and the distribution was strictly lobar in 13/16 patients (81%). Patients with preexisting CMBs with a strictly lobar distribution were significantly more likely to have new CMBs after IVT (p = 0.014). In the random-effects meta-analysis (n = 741), the pooled cumulative frequency of new CMBs after IVT was 4.4%. A higher preexisting CMB burden (>2) was associated with a higher likelihood of new CMBs (odds ratio [OR] 3.6, 95% confidence interval [CI] 1.3-10.3) and new CMBs were associated with the occurrence of remote parenchymal hemorrhage (OR 28.8, 95% CI 8.6-96.4).

CONCLUSIONS

New remote CMBs after IVT occurred in 4% of stroke patients, mainly had a strictly lobar distribution, and were associated with IVT-related hemorrhagic complications. Preexisting CMBs with a strictly lobar distribution and a higher CMB burden were associated with new CMBs after IVT, which may indicate an underlying cerebral amyloid angiopathy.

A Quantitative Comparison of Clinically Employed Parameters in the Assessment of Acute Cerebral Ischemia Using Dynamic Susceptibility Contrast Magnetic Resonance Imaging

Purpose: Perfusion magnetic resonance imaging (P-MRI) is part of the mismatch concept employed for therapy decisions in acute ischemic stroke. Using dynamic susceptibility contrast (DSC) MRI the time-to-maximum (Tmax) parameter is quite popular, but its inconsistently defined computation, arterial input function (AIF) selection, and the applied deconvolution method may introduce bias into the assessment. Alternatively, parameter free methods, namely, standardized time-to-peak (stdTTP), z_f-score, and standardized-z_f (stdZ) are also available, offering consistent calculation procedures without the need of an AIF or deconvolution.

Methods: Tmax was compared to stdTTP, z_f-, and stdZ to evaluate robustness of infarct volume estimation in 66 patients, using data from two different sites and MR systems (i.e., 1.5T vs. 3T; short TR (= 689 ms) vs. medium TR (= 1,390 ms); bolus dose 0.1 or 0.2 ml/kgBW, respectively).

Results: Quality factors (QF) for Tmax were 0.54 ± 0.18 (sensitivity), 0.90 ± 0.06 (specificity), and 0.87 ± 0.05 (accuracy). Though not significantly different, best specificity (0.93 ± 0.05) and accuracy (0.90 ± 0.04) were found for stdTTP with a sensitivity of 0.56 ± 0.17. Other tested parameters performed not significantly worse than Tmax and stdTTP, but absolute values of QFs were slightly lower, except for z_f showing the highest sensitivity (0.72 ± 0.16). Accordingly, in ROC-analysis testing the parameter performance to predict the final infarct volume, stdTTP and z_f showed the best performance. The odds for stdTTP to obtain the best prediction of the final infarct size, was 6.42 times higher compared to all other parameters (odds-ratio test; p = 2.2^*10–16).

Conclusion: Based on our results, we suggest to reanalyze data from large cohort studies using the parameters presented here, particularly stdTTP and zf-score, to further increase consistency of perfusion assessment in acute ischemic stroke.

Impact of pre-admission oral anticoagulation on ischaemic stroke volume, lesion pattern, and frequency of intracranial arterial occlusion in patients with atrial fibrillation

Aims

Therapeutic oral anticoagulation on hospital admission reduces morbidity and mortality after acute ischaemic stroke in patients with atrial fibrillation (AF). The underlying mechanism is not fully understood. In order to assess the impact of INR-level on admission on stroke volume, lesion pattern and the frequency of intracranial arterial occlusion, we analysed serial MRI measurements in AF patients suffering acute ischaemic stroke.

Methods and results

This subgroup analysis of the prospective '1000Plus' study included patients with acute ischaemic stroke and known AF or a first episode of AF in hospital. All patients underwent serial brain magnetic resonance imaging. Stroke patients were categorized as follows: Group1, phenprocoumon intake, international normalized ratio (INR) ≥1.7 on admission, no thrombolysis; Group2, INR < 1.7 on admission, thrombolysis; and Group3, INR < 1.7, no thrombolysis. In 98 AF patients {77 ± 9 years, 60% male; median National Institute of Health Stroke Scale [NIHSS] score on admission 5 (interquartile range [IQR] 2-8)} with known AF before admission, territorial infarction was less often found in Group 1 (n = 20) compared with Group 2 + 3 (20% vs. 47%, P = 0.022). Arterial occlusion rate on admission differed among groups (30%, 75%, and 35%, respectively, P = 0.004) but not between Group 1 vs. Group 2 + 3 (30% vs. 45%, P = 0.31). Median FLAIR volume on Days 5-7 was lower in Group1 compared with Group 2 (n = 20) [3.2 cm3 (IQR 1.1-11.3) vs. 18.6 cm3 (IQR 8.2-49.4); P = 0.009] but not compared with Group 2 + 3 [7.8 cm3 (IQR 1.6-25.9); P = 0.23]. An INR ≥ 1.7 on admission was not associated with smaller stroke volume in multivariable regression analysis. Adding 57 patients with a first AF episode during the in-hospital stay, similar results were observed in 155 AF patients.

Conclusion

In this AF cohort, an INR ≥ 1.7 at stroke onset affects lesion pattern but does not affect significantly lower stroke volume and the frequency of arterial occlusion on admission.

Left atrial appendage angiography is associated with the incidence and number of magnetic resonance imaging-detected brain lesions after percutaneous catheter-based left atrial appendage closure

BACKGROUND

Percutaneous catheter-based left atrial appendage closure (LAAC) is a procedure being increasingly performed in patients with atrial fibrillation and high bleeding risk.

OBJECTIVE

The purpose of this study was to evaluate the incidence of magnetic resonance imaging (MRI)-detected acute brain lesions (ABLs) as well as potential changes in neurocognitive function after percutaneous LAAC in patients with atrial fibrillation.

METHODS

Brain MRI at 3 T was performed within 24 hours before and after LAAC along with neurologic (National Institutes of Health Stroke Scale [NIHSS] score) and cognitive (Montreal Cognitive Assessment [MoCA] test) assessment. Acquired MRI sequences included high-resolution diffusion-weighted imaging as well as fluid-attenuated inversion recovery.

RESULTS

Successful device implantation was achieved in all 23 patients (age 74.1 ± 10.5 years; 16 male) using the Amulet (n = 18), Occlutech (n = 3), or LAmbre (n = 2) device. Thirty-seven ABLs were detected by MRI in 12 of 23 patients (52%) after LAAC. The number of periprocedural LAA angiographies was significantly higher in patients with ABL than in those without ABL (1.67 ± 0.65 vs 1.18 ± 0.41; P = .048) and was associated with a higher number of ABL (ρ = 0.615; P = .033). Compared to pre-LAAC assessment, post-LAAC MoCA and NIHSS scores revealed similar results. After LAAC, MoCA test (mean 24.1 ± 4.6 vs 23.2 ± 4.6; P = .09) and NIHSS score (mean 1.0 ± 1.7 vs 1.2 ± 1.8; P = .1) were similar between patients with and those without ABL, respectively.

CONCLUSION

MRI-detected ABLs are commonly observed after percutaneous LAAC. The number of LAA angiographies is significantly associated with the number of ABLs; however, the clinical implications of ABL have yet to be determined.

MRI-Guided Thrombolysis for Stroke with Unknown Time of Onset

BACKGROUND

Under current guidelines, intravenous thrombolysis is used to treat acute stroke only if it can be ascertained that the time since the onset of symptoms was less than 4.5 hours. We sought to determine whether patients with stroke with an unknown time of onset and features suggesting recent cerebral infarction on magnetic resonance imaging (MRI) would benefit from thrombolysis with the use of intravenous alteplase.

METHODS

In a multicenter trial, we randomly assigned patients who had an unknown time of onset of stroke to receive either intravenous alteplase or placebo. All the patients had an ischemic lesion that was visible on MRI diffusion-weighted imaging but no parenchymal hyperintensity on fluid-attenuated inversion recovery (FLAIR), which indicated that the stroke had occurred approximately within the previous 4.5 hours. We excluded patients for whom thrombectomy was planned. The primary end point was favorable outcome, as defined by a score of 0 or 1 on the modified Rankin scale of neurologic disability (which ranges from 0 [no symptoms] to 6 [death]) at 90 days. A secondary outcome was the likelihood that alteplase would lead to lower ordinal scores on the modified Rankin scale than would placebo (shift analysis).

RESULTS

The trial was stopped early owing to cessation of funding after the enrollment of 503 of an anticipated 800 patients. Of these patients, 254 were randomly assigned to receive alteplase and 249 to receive placebo. A favorable outcome at 90 days was reported in 131 of 246 patients (53.3%) in the alteplase group and in 102 of 244 patients (41.8%) in the placebo group (adjusted odds ratio, 1.61; 95% confidence interval [CI], 1.09 to 2.36; P=0.02). The median score on the modified Rankin scale at 90 days was 1 in the alteplase group and 2 in the placebo group (adjusted common odds ratio, 1.62; 95% CI, 1.17 to 2.23; P=0.003). There were 10 deaths (4.1%) in the alteplase group and 3 (1.2%) in the placebo group (odds ratio, 3.38; 95% CI, 0.92 to 12.52; P=0.07). The rate of symptomatic intracranial hemorrhage was 2.0% in the alteplase group and 0.4% in the placebo group (odds ratio, 4.95; 95% CI, 0.57 to 42.87; P=0.15).

CONCLUSIONS

In patients with acute stroke with an unknown time of onset, intravenous alteplase guided by a mismatch between diffusion-weighted imaging and FLAIR in the region of ischemia resulted in a significantly better functional outcome and numerically more intracranial hemorrhages than placebo at 90 days. (Funded by the European Union Seventh Framework Program; WAKE-UP ClinicalTrials.gov number, NCT01525290; and EudraCT number, 2011-005906-32 .).

Long-term follow up of 3 T MRI-detected brain lesions after percutaneous catheter-based left atrial appendage closure

BACKGROUND

Left atrial appendage closure (LAAC) for stroke prevention is an increasingly performed intervention.

AIMS

This prospective study aims to evaluate the incidence of long-term magnetic resonance imaging (MRI)-detected brain lesions as well as potential changes of neurocognitive function after percutaneous LAAC.

METHODS

Brain MRI at 3 T was performed within 24 hr before and after LAAC. A follow-up MRI was carried out after three months. Neuro-cognitive examination using the National Institutes of Health Stroke Scale (NIHSS) score and the Montreal Cognitive Assessment (MoCA) Test was performed.

RESULTS

Successful device implantation was achieved in all 25 patients (age 74.6 ± 10.2 years, male = 17) using the Amulet (n = 20), Occlutech (n = 3), or a Lambre (n = 2) device. In 12/25 (48%) patients, acute brain lesions (ABL) were detected after LAAC. A three-month follow-up MRI was performed in seven patients, and no new ABLs were seen. In 5/7 (71%) patients, there were no residual changes from the ABLs detectable. However, the FLAIR sequence was still positive in two patients. After LAAC, there were no significant differences in the MoCA-test (mean 24.3 ± 4.5 vs. 23.5 ± 4.5; P = 0.1) and the NIHSS-score (mean 0.9 ± 1.6 vs. 1.2 ± 1.8; P = 0.1). This was the same at the three-month follow-up (MoCA-test 23.5 ± 4.5 vs. 23.8 ± 2.7; P = 0.3; NIHSS-score 1.2 ± 1.8 vs. 1.0 ± 0.8; P = 0.4).

CONCLUSION

While new MRI-detected brain lesions are commonly observed after percutaneous LAAC, ABLs were no longer detectable in 71% of the patients at the three-month follow-up. There were no significant changes in neurocognitive function after LAAC and at the three-month follow-up.

Effects of Prehospital Thrombolysis in Stroke Patients With Prestroke Dependency

Background and Purpose—

Data on effects of intravenous thrombolysis on outcome of patients with ischemic stroke who are dependent on assistance in activities of daily living prestroke are scarce. Recent registry based analyses in activities of daily –independent patients suggest that earlier start of intravenous thrombolysis in the prehospital setting leads to better outcomes when compared with the treatment start in hospital. We evaluated whether these observations can be corroborated in patients with prestroke dependency.

Methods—

This observational, retrospective analysis included all patients with acute ischemic stroke depending on assistance before stroke who received intravenous thrombolysis either on the Stroke Emergency Mobile (STEMO) or through conventional in-hospital care (CC) in a tertiary stroke center (Charité, Campus Benjamin Franklin, Berlin) during routine care. Prespecified outcomes were modified Rankin Scale scores of 0 to 3 and survival at 3 months, as well as symptomatic intracranial hemorrhage. Outcomes were adjusted in multivariable logistic regression.

Results—

Between February 2011 and March 2015, 122 of 427 patients (28%) treated on STEMO and 142 of 505 patients (28%) treated via CC needed assistance before stroke. Median onset-to-treatment times were 97 (interquartile range, 69–159; STEMO) and 135 (interquartile range, 98–184; CC; P <0.001) minutes. After 3 months, modified Rankin Scale scores of 0 to 3 was observed in 48 STEMO patients (39%) versus 35 CC patients (25%; P =0.01) and 86 (70%, STEMO) versus 85 (60%, CC) patients were alive ( P =0.07). After adjustment, STEMO care was favorable with respect to modified Rankin Scale scores of 0 to 3 (odds ratio, 1.99; 95% confidence interval, 1.02–3.87; P =0.042) with a nonsignificant result for survival (odds ratio, 1.73; 95% confidence interval, 0.95–3.16; P =0.07). Symptomatic intracranial hemorrhage occurred in 5 STEMO versus 12 CC patients (4.2% versus 8.5%; P =0.167).

Conclusions—

The results of this study suggest that earlier, prehospital (as compared with in-hospital) start of intravenous thrombolysis in acute ischemic stroke may translate into better clinical outcome in patients with prestroke dependency.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT02358772.

Characteristics associated with outcome in patients with first-ever posterior fossa stroke

BACKGROUND AND PURPOSE

Factors such as infarct volume, infarct location and symptom severity can considerably influence long-term outcome in posterior fossa strokes. The decision about therapy can sometimes be complicated by discrepancies between infarct volume and clinical severity. We aimed to evaluate imaging and clinical parameters possibly influencing long-term outcome in patients with first-ever posterior fossa stroke.

METHODS

Imaging was performed on a 3-T magnetic resonance imaging scanner. Sixty-one of 1795 patients from the observational 1000Plus and LOBI studies (NCT00715533 and NCT02077582, clinicaltrials.org) were enrolled, meeting the inclusion criteria of first-ever posterior fossa stroke and magnetic resonance imaging examination within 24 h after symptom onset. Infarcts were classified as belonging to a proximal, middle or distal territory location in the posterior fossa. Good outcome was defined as a modified Rankin scale score of ≤1 at 3 months.

RESULTS

The largest lesion volumes on diffusion-weighted imaging on day 0 and fluid attenuation inversion recovery (FLAIR) on day 6 were found in the middle territory location with a median volume of 0.4 mL on diffusion-weighted imaging and 1.0 mL on FLAIR on day 6 versus 0.1/0.3 mL in the proximal and 0.1/0.1 mL in the distal territory location of the posterior fossa, respectively. Parameters associated with poor outcome were older age (P = 0.005), higher National Institutes of Health Stroke Scale score on admission/discharge (P = 0.016; P = 0.001), larger lesion volumes on FLAIR on day 6 (P = 0.013) and dysphagia (P = 0.02). There was no significant association between infarct location and modified Rankin scale score on day 90.

CONCLUSION

Infarct volume and clinical severity, but not infarct location, were the main contributors to poor long-term outcome in first-ever posterior fossa strokes.

The ratio between cerebral blood flow and Tmax predicts the quality of collaterals in acute ischemic stroke

Background

In acute ischemic stroke the status of collateral circulation is a critical factor in determining outcome. We propose a less invasive alternative to digital subtraction angiography for evaluating collaterals based on dynamic-susceptibility contrast magnetic resonance imaging.

Methods

Perfusion maps of Tmax and cerebral blood flow (CBF) were created for 35 patients with baseline occlusion of a major cerebral artery. Volumes of hypoperfusion were defined as having a Tmax delay of > 4 seconds (Tmax4s) and > 6 seconds (Tmax6s) and a CBF drop below 80% of healthy, contralateral tissue. For each patient a ratio between the volume of the CBF and the Tmax based perfusion deficit was calculated. Associations with collateral status and radiological outcome were assessed with the Mann-Whitney-U test, uni- and multivariable logistic regression analyses as well as area under the receiver-operator-characteristic (ROC) curve.

Results

The CBF/Tmax volume ratios were significantly associated with bad collateral status in crude logistic regression analysis as well as with adjustment for NIHSS at admission and baseline infarct volume (OR = 2.5 95% CI[1.2–5.4] p = 0.020 for CBF/Tmax 4s volume ratio and OR = 1.6 95% CI[1.0–2.6] p = 0.031 for CBF/Tmax6s volume ratio). Moreover, the ratios were significantly correlated to final infarct size (Spearman’s rho = 0.711 and 0.619, respectively for the CBF/Tmax4s volume ratio and CBF/Tmax6s volume ration, all p<0.001). The ratios also had a high area under the ROC curve of 0.93 95%CI[0.86–1.00]) and 0.90 95%CI[0.80–1.00]respectively for predicting poor radiological outcome.

Conclusions

In the setting of acute ischemic stroke the CBF/Tmax volume ratio can be used to differentiate between good and insufficient collateral circulation without the need for invasive procedures like conventional angiography.

Assessment of thrombus length in acute ischemic stroke by post-contrast magnetic resonance angiography

OBJECTIVES

Post-contrast magnetic resonance angiography (PC-MRA) enables visualization of vessel segments distal to an intra-arterial thrombus in acute ischemic stroke. We hypothesized that PC-MRA also allows clot length measurement in different intracranial vessels.

METHODS

Patients with MRI-confirmed ischemic stroke and intracranial artery occlusion within 24 hours of symptom onset were prospectively evaluated. PC-MRA was added to a standard stroke MRI protocol. Thrombus length was measured on thick slab maximum intensity projection images. Clinical outcome at hospital discharge was assessed by modified Rankin Scale (mRS).

RESULTS

Thirty-four patients (median age 72 years) presenting with a median National Institutes of Health Stroke Scale score of 11 and a median onset to imaging time of 116 min were included. PC-MRA enabled precise depiction of proximal and distal terminus of the thrombus in 31 patients (91%), whereas in three patients (9%) PC-MRA presented a partial occlusion. Median thrombus length in patients with complete occlusion was 9.9 mm. In patients with poor outcome (mRS ≥3) median thrombus length was significantly longer than in those with good outcome (mRS ≤2;P=0.011).

CONCLUSIONS

PC-MRA demonstrates intra-arterial thrombus length at different vessel occlusion sites. Longer thrombus length is associated with poor clinical outcome.

CLINICAL TRIAL REGISTRATION

NCT02077582; Results.

Relationship Between Changes in the Temporal Dynamics of the Blood-Oxygen-Level-Dependent Signal and Hypoperfusion in Acute Ischemic Stroke

Background and Purpose—

Changes in the blood-oxygen-level-dependent (BOLD) signal provide a noninvasive measure of blood flow, but a detailed comparison with established perfusion parameters in acute stroke is lacking. We investigated the relationship between BOLD signal temporal delay and dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) in stroke patients.

Methods—

In 30 patients with acute (<24 hours) ischemic stroke, we performed Pearson correlation and multiple linear regression between DSC-MRI parameters (time to maximum [Tmax], mean transit time, cerebral blood flow, and cerebral blood volume) and BOLD-based parameters (BOLD delay and coefficient of BOLD variation). Prediction of severe hypoperfusion (Tmax >6 seconds) was assessed using receiver–operator characteristic (ROC) analysis.

Results—

Correlation was highest between Tmax and BOLD delay (venous sinus reference; time shift range 7; median r =0.60; interquartile range=0.49–0.71). Coefficient of BOLD variation correlated with cerebral blood volume (median r = 0.37; interquartile range=0.24–0.51). Mean R 2 for predicting BOLD delay by DSC-MRI was 0.54 (SD=0.2) and for predicting coefficient of BOLD variation was 0.37 (SD=0.17). BOLD delay (whole-brain reference, time shift range 3) had an area under the curve of 0.76 for predicting severe hypoperfusion (sensitivity=69.2%; specificity=80%), whereas BOLD delay (venous sinus reference, time shift range 3) had an area under the curve of 0.76 (sensitivity=67.3%; specificity=83.5%).

Conclusions—

BOLD delay is related to macrovascular delay and microvascular hypoperfusion, can identify severely hypoperfused tissue in acute stroke, and is a promising alternative to gadolinium contrast agent–based perfusion assessment in acute stroke.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00715533 and NCT02077582.

DCE-MRI blood–brain barrier assessment in acute ischemic stroke

Objective:

To quantitatively evaluate blood–brain barrier changes in ischemic stroke patients using dynamic contrast-enhanced (DCE) MRI.

Methods:

We examined 54 stroke patients (clinicaltrials.govNCT00715533, NCT02077582) in a 3T MRI scanner within 48 hours after symptom onset. Twenty-eight patients had a follow-up examination on day 5–7. DCE T1 mapping and Patlak analysis were employed to assess BBB permeability changes.

Results:

Median stroke Ktrans values (0.7 × 10−3 min−1 [interquartile range (IQR) 0.4–1.8] × 10−3 min−1) were more than 3-fold higher compared to median mirror Ktrans values (0.2 × 10−3 min−1, IQR 0.1–0.7 × 10−3 min−1, p < 0.001) and further increased at follow-up (n = 28, 2.3 × 10−3 min−1, IQR 0.8–4.6 × 10−3 min−1, p < 0.001). By contrast, mirror Ktrans values decreased over time with a clear interaction of timepoint and stroke/mirror side (p < 0.001). Median stroke Ktrans values were 2.5 times lower than in hemorrhagic transformed regions (0.7 vs 1.8 × 10−3 min−1; p = 0.055). There was no association between stroke Ktrans values and the delay from symptom onset to baseline examination, age, and presence of hyperintense acute reperfusion marker.

Conclusion:

BBB in acute stroke patients can be successfully assessed quantitatively. The decrease of BBB permeability in unaffected regions at follow-up may be an indicator of global BBB leakage even in vessel territories remote from the index infarct.

Glial Fibrillary Acidic Protein for Prehospital Diagnosis of Intracerebral Hemorrhage

BACKGROUND

Both, acute ischemic stroke (AIS) and hemorrhage stroke (intracerebral hemorrhage, ICH) require early attention but different treatment strategies. Plasma glial fibrillary acidic protein (GFAP) levels were found to be elevated in ICH patients after they arrived in the hospital. Because treatment options differed, we sought to determine whether GFAP can be used to accurately differentiate between of AIS and ICH in the prehospital setting.

METHODS

We assessed acute stroke patients in the Stroke Emergency Mobile (STEMO). STEMO is a stroke ambulance staffed by a specialized team including a neurologist and equipped with a computed tomography scanner plus a point-of-care laboratory. The STEMO ambulance is integrated in the emergency medical system of Berlin, Germany. Following prehospital stroke diagnosis, blood was drawn and subsequently analysed using research assays from Roche diagnostics. The clinical accuracy of plasma GFAP was tested using a cut-off value of 0.29 ng/ml.

RESULTS

Blood samples of 74 patients were analysed. Twenty-five patients had ICH (mean age 69 ± 11 years, median National Institutes of Health Stroke Scale (NIHSS) 15) and 49 IS (mean age 75 ± 10 years, median NIHSS 6). Nine ICH (0 IS patients) had GFAP-levels above 0.29 ng/ml. The sensitivity and specificity of GFAP for differentiating between ICH and AIS were 36.0 and 100%. The sensitivity for ICH volume >15 ml was 61.5%. ICH patients without GFAP elevation had significantly smaller hemorrhage volumes (median 4.5 vs. 37.6 ml, p = 0.004) and were less likely to deteriorate (19 vs. 56%, p = 0.087).

CONCLUSIONS

GFAP levels >0.29 ng/ml were seen only in ICH, thus confirming the diagnosis of ICH during prehospital care. However, sensitivity is low particularly in smaller hemorrhages.

Right insular infarction and mortality after ischaemic stroke

BACKGROUND AND PURPOSE

Several studies have described an association between insular infarction and mortality. Large infarcts often include the insula and lesion size is associated with mortality. We hypothesized that there is an association between insular infarction and mortality independent of lesion volume.

METHODS

We included consecutive stroke patients between 1 September 2008 and 11 November 2012 from the 1000Plus database with an acute ischaemic lesion on diffusion-weighted imaging on day 1 and a completed 90-day follow-up. Insular infarct location was determined using the in-house software Stroke Lesion Atlas. In multiple Cox regression analysis (dependent variable: mortality), we adjusted for insular infarcts, age, lesion volume, history of atrial fibrillation, National Institutes of Health Stroke Scale and previous stroke.

RESULTS

We included 736 patients, of whom 168 had an insular infarction. Within a medium follow-up time of 107 days, cumulative survival was 90% in patients with insular infarction and 99% in patients without insular infarction (P < 0.001). Right insular infarction was independently associated with mortality (hazard ratio, 2.60; confidence interval, 1.3-5.4; P = 0.010).

CONCLUSIONS

In our study, right insular involvement was a prognostic marker for mortality after ischaemic stroke. A selection bias towards patients able to give informed consent warrants further studies.

Sensitivity of Diffusion-Weighted STEAM MRI and EPI-DWI to Infratentorial Ischemic Stroke

OBJECTIVES

To assess the sensitivity of stimulated echo acquisition mode diffusion weighted imaging (STEAM-DWI) to ischemic stroke in comparison to echo-planar imaging diffusion weighted imaging (EPI-DWI) in the infratentorial compartment.

METHODS

Fifty-seven patients presenting with clinical features of infratentorial stroke underwent STEAM-DWI, high-resolution EPI-DWI (HR-DWI, 2.5 mm slice thickness) and low-resolution EPI-DWI (LR-DWI, 5 mm slice thickness). Four readers assessed the presence of ischemic lesions and artifacts. Agreement between sequences and interobserver agreement on the presence of ischemia were calculated. The sensitivities of the DWI sequences were calculated in 45 patients with a confirmed diagnosis of infratentorial stroke.

RESULTS

Median time from symptom onset to imaging was 24 hours. STEAM-DWI agreed with LR-DWI in 89.5% of cases (kappa = 0.72, p<0.0001) and with HR-DWI in 89.5% of cases (kappa = 0.68, p<0.0001). STEAM-DWI showed fewer intraparenchymal artifacts (1/57) than HR-DWI (44/57) and LR-DWI (41/57). Ischemia was visible in 87% of cases for LR-DWI, 93% of cases for HR-DWI, and 89% of cases for STEAM-DWI. Interobserver agreement was good for STEAM-DWI (kappa = 0.62, p<0.0001).

CONCLUSIONS

Compared to the best currently available MR sequence for detecting ischemia (HR-DWI), STEAM-DWI shows fewer artifacts and a similar sensitivity to infratentorial stroke.

Optimising MR perfusion imaging: comparison of different software-based approaches in acute ischaemic stroke

OBJECTIVES

Perfusion imaging (PI) is susceptible to confounding factors such as motion artefacts as well as delay and dispersion (D/D). We evaluate the influence of different post-processing algorithms on hypoperfusion assessment in PI analysis software packages to improve the clinical accuracy of stroke PI.

METHODS

Fifty patients with acute ischaemic stroke underwent MRI imaging in the first 24 h after onset. Diverging approaches to motion and D/D correction were applied. The calculated MTT and CBF perfusion maps were assessed by volumetry of lesions and tested for agreement with a standard approach and with the final lesion volume (FLV) on day 6 in patients with persisting vessel occlusion.

RESULTS

MTT map lesion volumes were significantly smaller throughout the software packages with correction of motion and D/D when compared to the commonly used approach with no correction (p = 0.001-0.022). Volumes on CBF maps did not differ significantly (p = 0.207-0.925). All packages with advanced post-processing algorithms showed a high level of agreement with FLV (ICC = 0.704-0.879).

CONCLUSIONS

Correction of D/D had a significant influence on estimated lesion volumes and leads to significantly smaller lesion volumes on MTT maps. This may improve patient selection.

KEY POINTS

• Assessment on hypoperfusion using advanced post-processing with correction for motion and D/D. • CBF appears to be more robust regarding differences in post-processing. • Tissue at risk is estimated more accurately by correcting software algorithms. • Advanced post-processing algorithms show a higher agreement with the final lesion volume.

Abstract 179: Functional Outcomes of Pre-hospital Stroke Thrombolysis Compared to Conventional Care; the Stroke Emergency Mobile (STEMO) Project

Background: Specialized CT-equipped stroke ambulances can shorten time to intravenous thrombolysis (IVT) in acute ischemic stroke. Although efficacy of thrombolytic treatment is known to be time-sensitive, effects of pre-hospital thrombolysis on functional outcomes have not yet been evaluated.

Methods: We compared outcomes of all consecutive stroke patients who received thrombolysis during the same period cared for either by the Berlin Stroke Emergency Mobile (STEMO) or within conventional care (normal ambulance and in-hospital thrombolysis). Treatment and outcomes were documented in prospective registries. Patients who lived at home without assistance prior to their stroke were included. Primary outcome was modified Rankin Scale (mRS) ≤1 at 3 month. Secondary outcome was 3-month mortality. Outcomes were adjusted in multivariable regression for demographics, co-morbidities and stroke severity.

Results: From Feb. 5, 2011 to Mar 5, 2015, 427 patients were treated on STEMO and 513 in conventional care. 303 (mean age: 71y, female gender: 48%, median NIHSS: 7) and 357 (mean age: 70y, female gender: 36%, median NIHSS: 7) of them had lived at home without assistance pre-stroke, respectively. Mean onset to treatment time was 34 minutes shorter in STEMO care (96±60 vs. 130±56min). The primary outcome of mRS≤1 was observed in 167 (55%) and 168 (47%) patients (p=0.039); 17 (6%) vs 38 (11%) had died (p=0.02), respectively. Adjusted odds ratios were favorable for STEMO care: OR 1.56 (95%-CI: 1.11-2.20; p=0.01) for mRS≤1 and OR 0.50 (95%-CI: 0.26-0.98; p=0.04) for death.

Conclusions: The data suggest that earlier start of IVT by specialized prehospital stroke care leads to improved outcome.

Abstract TP47: Inverse PWI/DWI Mismatch is a Typical Feature of Acute Subcortical Ischemic Stroke

Introduction / Hypothesis: Diffusion/perfusion mismatch (MM) is commonly used to assess tissue at risk in stroke patients. In small subcortical infarcts (SSI) the reverse pattern i.e. “inverse mismatch” (IM) has been shown [1]. We aimed to evaluate the frequency and characteristics of IM in a larger cohort using two different perfusion diffusion analysis approaches.

Methods: We enrolled 129 patients with SSI within 24 hours of symptom onset (1000+ study, NCT00715533) comprising 44 infarcts of the thalamus, 9 located juxtacortically, 58 in the anterior choroidal artery, 18 in the lenticulostriate territory. Lesion volumes were assessed on DWI images using AnToNIa software. To evaluate perfusion maps a time-shift insensitive technique using a block-circulant matrix for deconvolution (oSVD) [2] was employed. Perfusion lesions were evaluated on MTT and Tmax (delay >2s and >6s) maps. A perfusion/diffusion ratio of 0.7 was used to define IM and 1.3 to define mismatch (MM).

Results: Results are summarized in table1. For all types of data analysis and all time points, IM was the by far most frequent pathophysiological pattern. Obviously, IM was seen most often at Tmax>6s, but it was still clearly observed with looser thresholds (Tmax>2s, MTT). At earlier time of onset IM occurred less often, but was still the most frequent pattern (p=0.0026). No significant association between infarct location and perfusion pattern was observed

Conclusion: IM is the most common pathophysiological constellation in SSI. We hypothesize that this is due to a lack of collateral circulation in these “endstream infarcts” and that the diffusion changes in areas without perfusion deficit reflect cytotoxic mechanisms.

1. Doege CA et al. AJNR 2003;24:1355-63

2. Wu O et al. Magn Reson Med 2003;50:164-174

Spot Sign in Acute Intracerebral Hemorrhage in Dynamic T1-Weighted Magnetic Resonance Imaging

BACKGROUND AND PURPOSE

In computed tomographic imaging of acute intracerebral hemorrhage spot sign on computed tomographic angiography has been established as a marker for hematoma expansion and poor clinical outcome. Although, magnetic resonance imaging (MRI) can accurately visualize acute intracerebral hemorrhage, a corresponding MRI marker is lacking to date.

METHODS

We prospectively examined 50 consecutive patients with acute intracerebral hemorrhage within 24 hours of symptom onset. The MRI protocol consisted of a standard stroke protocol and dynamic contrast-enhanced T1-weighted imaging with a time resolution of 7.07 s/batch. Stroke scores were assessed at admission and at time of discharge. Volume measurements of hematoma size and spot sign were performed with MRIcron.

RESULTS

Contrast extravasation within sites of the hemorrhage (MRI spot sign) was seen in 46% of the patients. Patients with an MRI spot sign had a significantly shorter time to imaging than those without (P<0.001). The clinical outcome measured by the modified Rankin Scale was significantly worse in patients with spot sign compared with those without (P≤0.001). Hematoma expansion was observed in the spot sign group compared with the nonspot sign group, although the differences were not significant.

CONCLUSIONS

Spot sign can be detected using MRI on postcontrast T1-weighted and dynamic T1-weighted images. It is associated with worse clinical outcome. The time course of contrast extravasation in dynamic T1 images indicates that these spots represent ongoing bleeding.