Functional contrast-enhanced CT for evaluation of acute ischemic stroke does not increase the risk of contrast-induced nephropathy

BACKGROUND AND PURPOSE

Concerns have recently grown regarding the safety of iodinated contrast agents used for CTA and CTP imaging. We tested whether the incidence of AN, defined by a >or=25% increase in the post-contrast scan creatinine level, was higher among patients with ischemic stroke who underwent a functional contrast-enhanced CT protocol compared with those who had no iodinated contrast administration.

MATERIALS AND METHODS

The contrast-exposed group consisted of 575 patients with acute ischemic stroke who underwent CTA (n = 313), CTA/CTP (n = 224), or CTA/CTP followed by conventional angiography (n = 38) within 24 hours of stroke onset and were consecutively enrolled in a prospective cohort study. The nonexposed group consisted of 343 patients with ischemic stroke, consecutively admitted to the same institution, who did not receive iodinated contrast material. Patients were stratified by baseline eGFR. In the primary analysis, the Fisher exact test was used to compare the incidence of AN between the contrast-exposed and the nonexposed patients at 24, 48, and 72 hours and on a cumulative basis. A secondary analysis compared the incidence of AN in patients who underwent conventional angiography following CTA/CTP versus patients who underwent CTA/CTP only.

RESULTS

The incidence of AN was 5% in the exposed and 10% in the nonexposed group (P = .003). Patients who underwent conventional angiography after contrast CT were at no greater risk of AN than patients who underwent CTA/CTP alone (26 patients, 5%; and 2 patients, 5%, respectively; P = .7).

CONCLUSIONS

Administration of a contrast-enhanced CT protocol involving CTA/CTP and conventional angiography in selected patients does not appear to increase the incidence of CIN.

A score to predict early risk of recurrence after ischemic stroke

BACKGROUND

There is currently no instrument to stratify patients presenting with ischemic stroke according to early risk of recurrent stroke. We sought to develop a comprehensive prognostic score to predict 90-day risk of recurrent stroke.

METHODS

We analyzed data on 1,458 consecutive ischemic stroke patients using a Cox regression model with time to recurrent stroke as the response and clinical and imaging features typically available to physician at admission as covariates. The 90-day risk of recurrent stroke was calculated by summing up the number of independent predictors weighted by their corresponding beta-coefficients. The resultant score was called recurrence risk estimator at 90 days or RRE-90 score (available at: http://www.nmr.mgh.harvard.edu/RRE-90/).

RESULTS

Sixty recurrent strokes (54 had baseline imaging) occurred during the follow-up period. The risk adjusted for time to follow-up was 6.0%. Predictors of recurrence included admission etiologic stroke subtype, prior history of TIA/stroke, and topography, age, and distribution of brain infarcts. The RRE-90 score demonstrated adequate calibration and good discrimination (area under the ROC curve [AUC] = 0.70-0.80), which was maintained when applied to a separate cohort of 433 patients (AUC = 0.70-0.76). The model's performance was also maintained for predicting early (14-day) risk of recurrence (AUC = 0.80).

CONCLUSIONS

The RRE-90 is a Web-based, easy-to-use prognostic score that integrates clinical and imaging information available in the acute setting to quantify early risk of recurrent stroke. The RRE-90 demonstrates good predictive performance, suggesting that, if validated externally, it has promise for use in creating individualized patient management algorithms and improving clinical practice in acute stroke care.

Clinical predictors of significant findings on head computed tomographic angiography

BACKGROUND

Although head computed tomographic angiography (CTA) is a sensitive tool for the evaluation of neurological symptoms in the emergency department (ED), little is known about which clinical signs predict significant CTA findings.

OBJECTIVES

To identify clinical factors that predict significant findings on head CTA in patients presenting to the ED with neurological complaints.

METHODS

Retrospective chart review of consecutive adult patients undergoing head CTA over a 6-month period in an urban, tertiary care ED with an annual volume of 76,000. Significant head CTA findings were defined as clinically significant neurological abnormalities undetected by previous imaging studies. Demographics, chief complaint, results of the neurological examinations (NE), and head non-contrast computed tomography (CT) results were used as predictors of significant head CTA. All predictors with a univariate p < 0.2 using Pearson's chi-squared were entered stepwise into a multivariable logistic regression including odds ratios (OR), with inclusion restricted to p < 0.05.

RESULTS

Chart review yielded 456 cases; 215 (47%) were male. Mean age was 62 (SD 20) years. There were 189 patients (41%) with abnormal CTAs. Multivariable logistic regression indicated five variables that predicted a clinically significant CTA: abnormal CT (OR 3.72), chief complaint of subarachnoid hemorrhage-type headache (OR 2.30), and motor deficit (OR 2.23), visual deficit (OR 2.23), and other focal deficit (OR 2.18) on NE. A chief complaint of trauma (OR 0.23) predicted a normal CTA.

CONCLUSIONS

Specific historical and focal neurological findings are useful for predicting clinically significant findings on head CTA.

Significance of large vessel intracranial occlusion causing acute ischemic stroke and TIA

BACKGROUND AND PURPOSE

Acute ischemic stroke due to large vessel occlusion (LVO)-vertebral, basilar, carotid terminus, middle and anterior cerebral arteries-likely portends a worse prognosis than stroke unassociated with LVO. Because little prospective angiographic data have been reported on a cohort of unselected patients with stroke and with transient ischemic attack, the clinical impact of LVO has been difficult to quantify.

METHODS

The Screening Technology and Outcome Project in Stroke Study is a prospective imaging-based study of stroke outcomes performed at 2 academic medical centers. Patients with suspected acute stroke who presented within 24 hours of symptom onset and who underwent multimodality CT/CT angiography were approached for consent for collection of clinical data and 6-month assessment of outcome. Demographic and clinical variables and 6-month modified Rankin Scale scores were collected and combined with blinded interpretation of the CT angiography data. The OR of each variable, including occlusion of intracranial vascular segment in predicting good outcome and 6-month mortality, was calculated using univariate and multivariate logistic regression.

RESULTS

Over a 33-month period, 735 patients with suspected stroke were enrolled. Of these, 578 were adjudicated as stroke and 97 as transient ischemic attack. Among patients with stroke, 267 (46%) had LVO accounting for the stroke and 13 (13%) of patients with transient ischemic attack had LVO accounting for transient ischemic attack symptoms. LVO predicted 6-month mortality (OR, 4.5; 95% CI, 2.7 to 7.3; P<0.001). Six-month good outcome (modified Rankin Scale score <or=2) was negatively predicted by LVO (0.33; 0.24 to 0.45; P<0.001). Based on multivariate analysis, the presence of basilar and internal carotid terminus occlusions, in addition to National Institutes of Health Stroke Scale and age, independently predicted outcome.

CONCLUSIONS

Large vessel intracranial occlusion accounted for nearly half of acute ischemic strokes in unselected patients presenting to academic medical centers. In addition to age and baseline stroke severity, occlusion of either the basilar or internal carotid terminus segment is an independent predictor of outcome at 6 months.

National Institutes of Health Stroke Scale score is poorly predictive of proximal occlusion in acute cerebral ischemia

BACKGROUND AND PURPOSE

Multimodal imaging is gaining an important role in acute stroke. The benefit of obtaining additional clinically relevant information must be weighed against the detriment of increased cost, delaying time to treatment, and adverse events such as contrast-induced nephropathy. Use of National Institutes of Health Stroke Scale (NIHSS) score to predict a proximal arterial occlusion (PO) is suggested by several case series as a viable method of selecting cases appropriate for multimodal imaging.

METHODS

Six hundred ninety-nine patients enrolled in a prospective cohort study involving CT angiographic imaging in acute stroke were dichotomized according to the presence of a PO, including a subgroup of 177 subjects with middle cerebral artery M1 occlusion.

RESULTS

The median NIHSS score of patients found to have a PO was higher than the overall median (9 versus 5, P<0.0001). The median NIHSS score of patients with middle cerebral artery M1 occlusion was 14. NIHSS score > or =10 had 81% positive predictive value for PO but only 48% sensitivity with the majority of subjects with PO presenting with lower NIHSS scores. All patients with NIHSS score > or =2 would need to undergo angiographic imaging to detect 90% of PO.

CONCLUSIONS

High NIHSS score correlates with the presence of a proximal arterial occlusion in patients presenting with acute cerebral ischemia. No NIHSS score threshold can be applied to select a subgroup of patients for angiographic imaging without failing to capture the majority of cases with clinically important occlusive lesions. The finding of minimal clinical deficits should not deter urgent angiographic imaging in otherwise appropriate patients suspected of acute stroke.

Collateral vessels on CT angiography predict outcome in acute ischemic stroke

BACKGROUND AND PURPOSE

Despite the abundance of emerging multimodal imaging techniques in the field of stroke, there is a paucity of data demonstrating a strong correlation between imaging findings and clinical outcome. This study explored how proximal arterial occlusions alter flow in collateral vessels and whether occlusion or extent of collaterals correlates with prehospital symptoms of fluctuation and worsening since onset or predict in-hospital worsening.

METHODS

Among 741 patients enrolled in a prospective cohort study involving CT angiographic imaging in acute stroke, 134 cases with proximal middle cerebral artery occlusion and 235 control subjects with no occlusions were identified. CT angiography was used to identify occlusions and grade the extent of collateral vessels in the sylvian fissure and leptomeningeal convexity. History of symptom fluctuation or progressive worsening was obtained on admission.

RESULTS

Prehospital symptoms were unrelated to occlusion or collateral status. In cases, 37.5% imaged within 1 hour were found to have diminished collaterals versus 12.1% imaged at 12 to 24 hours (P=0.047). No difference in worsening was seen between cases and control subjects with adequate collaterals, but cases with diminished sylvian and leptomeningeal collaterals experienced greater risk of worsening compared with control subjects measured either by admission to discharge National Institutes of Health Stroke Scale increase > or =1 (55.6% versus 16.6%, P=0.001) or > or =4 (44.4% versus 6.4%, P<0.001).

CONCLUSIONS

Most patients with proximal middle cerebral artery occlusion rapidly recruit sufficient collaterals and follow a clinical course similar to patients with no occlusions, but a subset with diminished collaterals is at high risk for worsening.

Severity of leukoaraiosis correlates with clinical outcome after ischemic stroke

BACKGROUND

Leukoaraiosis (LA) is closely associated with aging, a major determinant of clinical outcome after ischemic stroke. In this study we sought to identify whether LA, independent of advancing age, affects outcome after acute ischemic stroke.

METHODS

LA volume was quantified in 240 patients with ischemic stroke and MRI within 24 hours of symptom onset. We explored the relationship between LA volume at admission and clinical outcome at 6 months, as assessed by the modified Rankin Scale (mRS). An ordinal logistic regression model was developed to analyze the independent effect of LA volume on clinical outcome.

RESULTS

Bivariate analyses showed a significant correlation between LA volume and mRS at 6 months (r = 0.19, p = 0.003). Mean mRS was 1.7 +/- 1.8 among those in the lowest (< or =1.2 mL) and 2.5 +/- 1.9 in the highest (>9.9 mL) quartiles of LA volume (p = 0.01). The unfavorable prognostic effect of LA volume on clinical outcome was retained in the multivariable model (p = 0.002), which included age, gender, stroke risk factors (hypertension, diabetes mellitus, atrial fibrillation), previous history of brain infarction, admission plasma glucose level, admission NIH Stroke Scale score, IV rtPA treatment, and acute infarct volume on MRI as covariates.

CONCLUSIONS

The volume of leukoaraiosis is a predictor of clinical outcome after ischemic stroke and this relationship persists after adjustment for important prognostic factors including age, initial stroke severity, and infarct volume.

Admission international normalized ratio and acute infarct volume in ischemic stroke

OBJECTIVE

The level of anticoagulation at the time of stroke onset may influence the size, composition, and dissolution rate of the occlusive clot. We explored the relation between admission international normalized ratio (INR) and acute infarct volume in patients with ischemic stroke.

METHODS

We studied 93 consecutive patients with preadmission warfarin use who had INR measurement and diffusion-weighted imaging performed within 24 hours of stroke onset. Ninety-three etiologic stroke subtype-matched patients without prior warfarin use served as control patients. Linear regression analysis was used to test for independence of INR as a predictor of infarct volume.

RESULTS

In patients with preadmission warfarin use, admission INR was inversely correlated with lesion volume on diffusion-weighted imaging (r = -0.38). This relation was retained after adjustment for potential covariates (p = 0.014). INR less than 2.0 was associated with 3.5-fold (95% confidence interval, 2.9-4.2) greater lesion volume on diffusion-weighted imaging as compared with INR of 2.0 or more. Patients who were on therapeutic INR (>or=2.0) had smaller infarcts compared with patients without preadmission warfarin use (p = 0.001). Admission INR was inversely correlated with acute perfusion defect (r = -0.33), chronic infarct volume (r = -0.42), National Institutes of Health Stroke Scale score at admission (r = -0.27), and modified Rankin score at discharge (r = -0.28).

INTERPRETATION

These results suggest that preadmission warfarin use associated with therapeutic level of anticoagulation can offer a benefit in limiting the extent of ischemic injury in an event of acute stroke.

Clinical- and imaging-based prediction of stroke risk after transient ischemic attack: the CIP model

BACKGROUND AND PURPOSE

Predictive instruments based on clinical features for early stroke risk after transient ischemic attack suffer from limited specificity. We sought to combine imaging and clinical features to improve predictions for 7-day stroke risk after transient ischemic attack.

METHODS

We studied 601 consecutive patients with transient ischemic attack who had MRI within 24 hours of symptom onset. A logistic regression model was developed using stroke within 7 days as the response criterion and diffusion-weighted imaging findings and dichotomized ABCD(2) score (ABCD(2) >/=4) as covariates.

RESULTS

Subsequent stroke occurred in 25 patients (5.2%). Dichotomized ABCD(2) score and acute infarct on diffusion-weighted imaging were each independent predictors of stroke risk. The 7-day risk was 0.0% with no predictor, 2.0% with ABCD(2) score >/=4 alone, 4.9% with acute infarct on diffusion-weighted imaging alone, and 14.9% with both predictors (an automated calculator is available at http://cip.martinos.org). Adding imaging increased the area under the receiver operating characteristic curve from 0.66 (95% CI, 0.57 to 0.76) using the ABCD(2) score to 0.81 (95% CI, 0.74 to 0.88; P=0.003). The sensitivity of 80% on the receiver operating characteristic curve corresponded to a specificity of 73% for the CIP model and 47% for the ABCD(2) score.

CONCLUSIONS

Combining acute imaging findings with clinical transient ischemic attack features causes a dramatic boost in the accuracy of predictions with clinical features alone for early risk of stroke after transient ischemic attack. If validated in relevant clinical settings, risk stratification by the CIP model may assist in early implementation of therapeutic measures and effective use of hospital resources.

Physiological noise in MR images: an indicator of the tissue response to ischemia?

PURPOSE

To determine whether measuring signal intensity (SI) fluctuations in MRI time series data from acute stroke patients would identify ischemic tissue.

MATERIALS AND METHODS

Prebolus perfusion-weighted MRI data from 32 acute ischemic stroke patients (N = 32) was analyzed as a time series. Ischemic and normal tissue regions were outlined and compared.

RESULTS

The magnitude of the measured SI fluctuations was significantly lower in ischemic regions relative to normal tissue. Spatial differences in these fluctuations occurred in a manner that was different than other perfusion-based metrics.

CONCLUSION

Prior studies have shown that SI fluctuations in MRI time series data correspond to the presence of physiological "noise," which includes vasomotion, an autoregulatory phenomenon that affects the tissue response to ischemia. In this study, SI fluctuations were found to decrease in ischemia, consistent with the notion that small vessels will remain open (fluctuations in vessel diameter will decrease) when there is a challenge to flow. Spatial variation in SI fluctuations appeared to be different from spatial variation seen on other perfusion-based metrics, suggesting that a separate contrast mechanism is responsible, one that might be of diagnostic and prognostic value in acute stroke in which the ability of tissue to withstand ischemia is currently not well visualized.

Severity of Leukoaraiosis and Susceptibility to Infarct Growth in Acute Stroke

Background and Purpose— Leukoaraiosis (LA) is associated with structural and functional vascular changes that may compromise tissue perfusion at the microvascular level. We hypothesized that the volume of LA correlated with the proportion of initially ischemic but eventually infarcted tissue in acute human stroke.

Methods— We studied 61 consecutive patients with diffusion-weighted imaging–mean transit time mismatch. All patients were scanned twice within 12 hours of symptom onset and between days 4 and 30. We explored the relationship between the volume of white matter regions with LA on acute images and the proportion of diffusion-weighted imaging–mean transit time mismatch tissue that progressed to infarction (percentage mismatch lost).

Results— Bivariate analyses showed a statistically significant correlation between percentage mismatch lost and LA volume ( r =0.33, P <0.01). A linear regression model with percentage mismatch lost as response and LA volume, acute diffusion-weighted imaging and mean transit time volumes, age, admission blood glucose level, admission mean arterial blood pressure, etiologic stroke subtype, time to acute MRI, and time between acute and follow-up imaging as covariates revealed that LA volume was an independent predictor of infarct growth ( P =0.04). The adjusted percentage mismatch lost in the highest quartile of LA volume was 1.9-fold (95% CI: 1.2 to 3.1) greater than the percentage mismatch lost in the lowest quartile.

Conclusion— LA volume at the time of acute ischemic stroke is a predictor infarct growth. Because LA is associated with factors that modulate tissue perfusion as well as tissue capacity for handling of ischemia, LA volume appears to be a composite predictive marker for the fate of acutely ischemic tissue.

Outpatient practice patterns after stroke hospitalization among neurologists

BACKGROUND AND PURPOSE

Care after stroke hospitalization can provide several opportunities to optimize vascular risk reduction. However, not much is known about poststroke practice patterns among neurologists. Such knowledge may help direct specific efforts to improve the impact of practicing neurologists on clinical outcomes after stroke.

METHODS

A survey soliciting information on processes of care in the outpatient setting after recent hospitalization for ischemic stroke or transient ischemic attack was mailed to a random sample of 833 US and Canadian neurologist-members of the American Academy of Neurology.

RESULTS

A total of 475 (57%) responses were received. Practice demographics of survey responders and nonresponders were largely similar. Fourteen percent of respondents identified themselves as vascular neurologists. Overall, respondents reported frequently checking for medication adherence and counseling patients on lifestyle modification. However, neurologists reported screening more frequently for diabetes, hypertension, and dyslipidemia than actually treating these conditions (all P<0.0001) Vascular neurologists were more likely than general neurologists to screen for hypertension (97% versus 86%, P=0.016), dyslipidemia (94% versus 68%, P<0.001), diabetes (89% versus 62%, P<0.001), and sleep apnea (94% versus 79%, P=0.007) as well as to treat hypertension (71% versus 45%, P<0.001), dyslipidemia (82% versus 50%, P<0.001), diabetes (45% versus 21%, P<0.001), and current smoking (77% versus 59%, P=0.005). Neurologists with mostly government-insured and uninsured patients were significantly more likely to engage in vascular risk reduction treatment than neurologists with mostly commercially insured patients.

CONCLUSIONS

Self-reported rates of screening and treatment of major vascular risk factors by most neurologists after stroke hospitalization are substantial but not universal. Bridging knowledge gaps or adopting a systematic management approach in coordination with primary care physicians could help optimize poststroke care.

High-dose bosentan in the prevention and treatment of subarachnoid hemorrhage-induced cerebral vasospasm: an open-label feasibility study

OBJECTIVE

To evaluate the safety of high-dosages of the endothelin ET(A/B )receptor antagonist bosentan in SAH patients at high-vasospasm risk.

METHODS

Ten Fisher group-3 SAH patients, enrolled within 96 h of ictus, received bosentan in a dose-escalation manner (20, 30, 40 mg/kg/day orally every 4 hours on treatment days 1, 2, and 3 respectively, to a maximum dose of 4000 mg/day), followed by maintenance of the maximum tolerated dose until 14 days post-SAH or vasospasm resolution. Further management followed standard protocols: nimodipine in all patients; daily transcranial Doppler (TCD); "triple-H"/endovascular treatment, as indicated.

RESULTS

Two of the ten patients never developed any clinical or TCD signs of vasospasm; the other eight patients exhibited some elevation of TCD velocities during the vasospasm watch period. Four of the eight patients remained asymptomatic; of them, one had only mild elevation on peak systolic velocities, thought to represent hyperemia. The other three were further assessed with CT-angiography; this revealed moderate vasospasm (asymptomatic) in only one patient. The remaining four patients developed symptomatic vasospasm requiring endovascular treatment; two developed cerebral infarction; both had started bosentan relatively later than the other subjects. The most common adverse drug effects were flushing and transient liver enzyme elevations, reversible in all. Two patients had ALT/AST elevations >3x normal limit, requiring bosentan-dose reduction or discontinuation (one case each).

CONCLUSION

High-dose bosentan (up to 40 mg/kg/day) appears to be safe in SAH patients at high risk of developing vasospasm. Further studies are required to properly investigate the efficacy of this regimen in the prevention and treatment of SAH-induced vasospasm.

Stroke program review group: an interim report

The Stroke Program Review Group (SPRG) met for the first time in 2001 to identify and prioritize scientific needs and opportunities in stroke, and to consider strategies to address them. Out of this meeting came a set of scientific and resource recommendations (http://www.ninds.nih.gov/find_people/groups/stroke_prg/index.htm) including the recommendation to review progress after 5 years. In September 2006, the NINDS convened a second SPRG of prominent scientists, clinicians, industry leaders, and patient advocates to discuss progress since the first SPRG and to examine new opportunities in light of more recent advances. The report of the second SPRG meeting is found at http://www.ninds.nih.gov/find_people/groups/stroke_prg/09_2006_stroke_prg_report.htm. In this brief interim report, we list and summarize progress in each of the investigational domains outlined in the SPRG with an emphasis on those advances directly resulting from NINDS-funded research. Also listed are the top 2 or 3 research priorities for the next 5-year cycle for each investigational theme. What emerges from the first 2 reports is a clear set of priorities that have since been complemented by exciting advances that are likely to be the focus of a follow-up report from the next SPRG in 2010.

Interexaminer difference in infarct volume measurements on MRI: a source of variance in stroke research

BACKGROUND AND PURPOSE

The measurement of ischemic lesion volume on diffusion- (DWI) and perfusion-weighted MRI (PWI) is examiner dependent. We sought to quantify the variance imposed by measurement error in DWI and PWI lesion volume measurements in ischemic stroke.

METHODS

Fifty-eight consecutive patients with DWI and PWI within 12 hours of symptom onset and follow-up MRI on >or= day-5 were studied. Two radiologists blinded to each other measured lesion volumes by manual outlining on each image. Interexaminer reliability was evaluated by intraclass correlation coefficients (ICC) and relative paired difference or RPD (ratio of difference between 2 measurements to their mean). The ratio of between-examiner variability to between-subject variability (variance ratio) was calculated for each imaging parameter.

RESULTS

The correlation (ICC) between examiners ranged from 0.93 to 0.99. The median RPD was 10.0% for DWI, 14.1% for mean transit time, 18.9% for cerebral blood flow, 21.0% for cerebral blood volume, 16.8% for DWI/MTT mismatch, and 6.3% for chronic T2-weighted images. There was negative correlation between RPD and lesion volume in all but chronic T2-weighted images. The variance ratio ranged between 0.02 and 0.10.

CONCLUSIONS

Despite high correlation between volume measurements of abnormal regions on DWI and PWI by different examiners, substantial differences in individual measurements can still occur. The magnitude of variance from measurement error is primarily determined by the type of imaging and lesion volume. Minimizing this source of variance will better enable imaging to deliver on its promise of smaller sample size.

Middle Cerebral Artery Infarcts Encompassing the Insula Are More Prone to Growth

Background and Purpose— Based on previous observations that infarcts encompassing the insula were linked to unfavorable clinical outcome, we hypothesized that insular damage was directly associated with worsened infarction in ischemic but potentially viable neighboring brain tissue.

Methods— Using acute diffusion- and perfusion-weighted MRI within the first 12 hours of symptom onset and a follow-up MRI on day 5 or later, we calculated the percentage of mismatch lost (PML) in 61 consecutive patients with ischemic stroke within the middle cerebral artery territory. PML denoted the percentage of mismatch tissue between diffusion-weighted imaging and mean transit time maps that eventually underwent infarction. We explored the relationship between PML and insular location using a regression model.

Results— The median PML was 17.7% (interquartile range, 3.5% to 54.2%) in insular and 2.5% (0.0% to 12.7%) in noninsular infarcts ( P <0.01). The PML correlated with the volume of abnormal regions on diffusion-weighted imaging ( P <0.01), mean transit time ( P <0.01), cerebral blood flow maps ( P <0.01), and cerebral blood volume maps ( P <0.01). A linear regression model with PML as response and with acute MRI volumes, age, and the site of vascular occlusion as covariates showed that insular involvement was an independent predictor of PML ( P =0.01). The regression model predicted an approximately 3.2-fold increase in PML with insular involvement.

Conclusions— Infarction of the insula is associated with increased conversion of ischemic but potentially viable neighboring tissues into infarction. The unfavorable tissue outcome in insular infarcts may not be a mere bystander effect from proximal middle cerebral artery occlusions.

A Computerized Algorithm for Etiologic Classification of Ischemic Stroke

Background and Purpose— The SSS-TOAST is an evidence-based classification algorithm for acute ischemic stroke designed to determine the most likely etiology in the presence of multiple competing mechanisms. In this article, we present an automated version of the SSS-TOAST, the Causative Classification System (CCS), to facilitate its utility in multicenter settings.

Methods— The CCS is a web-based system that consists of questionnaire-style classification scheme for ischemic stroke (http://ccs.martinos.org). Data entry is provided via checkboxes indicating results of clinical and diagnostic evaluations. The automated algorithm reports the stroke subtype and a description of the classification rationale. We evaluated the reliability of the system via assessment of 50 consecutive patients with ischemic stroke by 5 neurologists from 4 academic stroke centers.

Results— The kappa value for inter-examiner agreement was 0.86 (95% CI, 0.81 to 0.91) for the 5-item CCS (large artery atherosclerosis, cardio-aortic embolism, small artery occlusion, other causes, and undetermined causes), 0.85 (95% CI, 0.80 to 0.89) with the undetermined group broken into cryptogenic embolism, other cryptogenic, incomplete evaluation, and unclassified groups (8-item CCS), and 0.80 (95% CI, 0.76 to 0.83) for a 16-item breakdown in which diagnoses were stratified by the level of confidence. The intra-examiner reliability was 0.90 (0.75–1.00) for 5-item, 0.87 (0.73–1.00) for 8-item, and 0.86 (0.75–0.97) for 16-item CCS subtypes.

Conclusions— The web-based CCS allows rapid analysis of patient data with excellent intra- and inter-examiner reliability, suggesting a potential utility in improving the fidelity of stroke classification in multicenter trials or research databases in which accurate subtyping is critical.

Magnetic Resonance Spectroscopy Study of Oxygen Therapy in Ischemic Stroke

BACKGROUND AND PURPOSE

Recent studies suggest that normobaric oxygen therapy (NBO) is neuroprotective in acute ischemic stroke.

METHODS

We performed multivoxel magnetic resonance spectroscopic imaging and diffusion/perfusion MRI in patients with stroke treated with NBO or room air. Imaging was performed before, during, and after therapy.

RESULTS

Voxel-based analysis showed excellent correlation between apparent diffusion coefficient values, lactate, and N-acetyl-aspartate levels at all time points. Lactate decreased during NBO and increased post-NBO. N-acetyl-aspartate decreased in patients receiving room air but not in NBO-treated patients.

CONCLUSIONS

These data suggest that NBO improves aerobic metabolism and preserves neuronal integrity in the ischemic brain.

Clinical diagnosis of lacunar stroke in the first 6 hours after symptom onset: analysis of data from the glycine antagonist in neuroprotection (GAIN) Americas trial

BACKGROUND AND PURPOSE

Although the pathophysiological heterogeneity of stroke may be highly relevant to the development of acute-phase therapies, discriminating between ischemic stroke subtypes soon after onset remains a challenge. We conducted a study of the accuracy of a clinical diagnosis of lacunar stroke in the first 6 hours after symptom onset.

METHODS

We analyzed data from 1367 patients in the Glycine Antagonist In Neuroprotection (GAIN) Americas trial. The Trial of ORG10172 in Acute Stroke Treatment (TOAST) category "small vessel (lacunar)" disease at day 7 or at hospital discharge was used as the reference standard to determine the accuracy of a diagnosis of a lacunar stroke made within 6 hours of symptom onset using the Oxfordshire Community Stroke Project (OCSP) classification "LACS." Outcome was analyzed by comparing the proportions of patients classified as "LACS" at baseline or "small vessel (lacunar)" at 7 days who were dead or dependent at 3 months.

RESULTS

The positive predictive value of an OCSP diagnosis of a lacunar stroke was 76% (95% CI: 69% to 81%; sensitivity 64% [95% CI: 58% to 70%]; specificity 96% [95% CI: 95% to 97%]; negative predictive value 93% [95% CI: 92% to 94%]; accuracy 91% [95% CI: 89% to 92%]). The 3-month outcomes of patients classified as either OCSP "LACS" within 6 hours of onset or TOAST "small vessel (lacunar)" at 7 days were not significantly different.

CONCLUSIONS

An OCSP LACS diagnosis made within 6 hours of stroke onset is reasonably predictive of a final diagnosis of "small vessel (lacunar)" disease made using TOAST criteria and has a similar relationship to outcome at 3 months.

Acute brain infarct: detection and delineation with CT angiographic source images versus nonenhanced CT scans

PURPOSE

To retrospectively compare sensitivity and specificity of admission nonenhanced computed tomographic (CT) scans with those of CT angiographic source images in detection of early ischemic changes in middle cerebral artery (MCA) stroke and to retrospectively compare admission nonenhanced CT scans with CT angiographic source images in delineation of final infarct extent, with follow-up images as reference.

MATERIALS AND METHODS

Informed consent and institutional review board approval were received for this HIPAA-compliant study. Nonenhanced scans and angiographic source images obtained within 12 hours of symptom onset in 51 patients suspected of having MCA stroke were reviewed. Two blinded neuroimagers rated presence and extent of hypoattenuation on nonenhanced scans and angiographic source images with Alberta Stroke Programme Early CT Score (ASPECTS). Level of certainty for hypoattenuation detection was assigned a grade with a five-point scale. With receiver operating characteristic (ROC) curve analysis, nonenhanced scans and angiographic source images were compared for stroke detection. For stroke delineation, linear regression coefficients determined correlations of ASPECTS for nonenhanced scans and angiographic source images with ASPECTS for follow-up images. Multiple linear regressions were used to compare these correlations.

RESULTS

Follow-up nonenhanced CT scans, diffusion-weighted magnetic resonance (MR) images, or fluid-attenuated inversion-recovery MR images were obtained (mean time to follow-up, 5.4 days); 33 patients had infarction. With level of certainty cutoff score of 4 or greater (probable, definite) for ischemic hypoattenuation, sensitivity for detection of acute stroke was 48% (nonenhanced scans) and 70% (angiographic source images) (P = .04, ROC analysis); specificity was 100% for both. Linear regression revealed R(2) = 0.42 (P < .001) for correlation between delineation of stroke on nonenhanced scans and on follow-up images evaluated with ASPECTS and 0.73 (P < .001) for correlation between delineation on angiographic source images and follow-up images evaluated with ASPECTS (P < .001, nonenhanced scans vs angiographic source images).

CONCLUSION

CT angiographic source images, compared with nonenhanced CT scans, are more sensitive in detection of early irreversible ischemia and more accurate for prediction of final infarct volume.