Acute Posterior Circulation Stroke Research Articles

Abstract 2972: Perfusion CT in Patients with Basilar Artery Occlusion: Diagnostic and Prognostic Value in the Basilar Artery International Cooperation Study

Background: The posterior circulation Acute Stroke Prognosis Early CT Score (pc-ASPECTS) applied to CT angiography source images (CTA-SI) predicts the functional outcome of patients with basilar artery occlusion (BAO). Compared with CTA-SI, perfusion CT (CTP) may provide added information. We assessed the diagnostic and prognostic impact of CTP compared with CTA-SI among patients in the Basilar Artery International Cooperation Study (BASICS) Methods: BASICS was a prospective observational registry of consecutive patients with acute symptomatic BAO. We applied pc-ASPECTS to CTA-SI and cerebral blood volume (CBV), cerebral blood flow (CBF), time-to-peak (TTP) and mean-transit-time (MTT) parameter maps in a 3-reader-consensus with readers blinded to clinical data. Hypoattenuation on CTA-SI, a relative reduction in CBV or CBF, or relative increase in MTT or TTP was rated as abnormal. Clinical outcome was measured with the modified Rankin Scale (mRS) score at 1 month. Results: Among 592 patients in the BASICS registry, 27 patients (4.6%) had CTP studies performed. Median (interquartile-range) pc-ASPECTS values on TTP/MTT, CTA-SI, CBF and CBV were 6 (5-8), 7 (5-9), 8 (6-9) and 10 (8.75-10), respectively (p<0.001). The proportion of patients with any perfusion abnormalities in the posterior circulation was highest for TTP/MTT (93%; CI 95% 74% to 99%), compared with 78% (CI 95% 57% to 91%) for both CTA-SI and CBF and 46% (CI 95% 27% to 66%) for CBV (p<0.001). At 1 month, 9 patients (33%) had a favourable outcome (mRS scores 0-3), 8 patients (30%) had an unfavourable outcome (mRS scores 4-5) and 10 patients (37%) were deceased. In univariate analysis, pc-ASPECTS scores did not correlate with outcome mRS scores for all imaging modalities (Spearman’s Rho, p>0.1 for all). All three patients (100%) with a CBV pc-ASPECTS <8 compared to 6 of 23 patients (26%) with a CBV pc-ASPECTS >8 died (p=0.03). Conclusion: CTP was performed in a minority of patients in the BASICS registry population. Perfusion disturbances in the posterior circulation were most frequent and most pronounced on TTP and MTT parameter maps. Extensive reduction of CBV, defined as a pc-ASPECTS <8, may indicate patients with a high case fatality.

MRI in Patients with Acute Basilar Artery Occlusion – DWI Lesion Scoring is an Independent Predictor of Outcome

We analyzed early diffusion-weighted magnetic resonance imaging of patients with acute basilar artery occlusion by applying different lesion scoring systems and determined their predictive value for favorable outcome. Between 1998 and 2010, patients with confirmed basilar artery occlusion were entered in a local database. magnetic resonance imaging angiography was performed for diagnosis of basilar artery occlusion and/or during initiated recanalization therapy. We analyzed the patients' clinical and radiological baseline data, recanalization, and favorable outcome modified Rankin Scale 0-2 after three-months. Diffusion weighted imaging findings were categorized into lesions in vascular territories as well as by two previously published scores for ischemic damage in the posterior circulation, the Renard score and posterior circulation Acute Stroke Prognosis Early computed tomography Score. Fifty patients with basilar artery occlusion received an early MRI, and in 30 of those, a follow-up MRI was performed. Median time to baseline MRI was 5·5 h (one-hour to 24 h). Median baseline Renard score and posterior circulation Acute Stroke Prognosis Early CT Score were 2·75 (0-10) and 7 (0-10), respectively. Of the patients, 82% received an acute recanalization therapy and in 78% of those, the basilar artery recanalized. Median time to therapy was five-hours (1·25-20 h). 24% of all patients had a favorable outcome (mRS 0-2). Patients with a favorable outcome had a lower Renard score and higher pcASPECTS, a lower rate of complete basilar artery occlusion, a higher Glasgow coma scale on admission, and a higher rate of successful recanalization (all P < 0·05). After logistic regression, the only independent predictor for favorable outcome was a posterior circulation Acute Stroke Prognosis Early CT Score of 8 or more points (odds ratio 3·9, 95% confidence interval 1·4-11·7, P < 0·05). In patients with acute basilar artery occlusion, posterior circulation Acute Stroke Prognosis Early CT Score of 8 or more points on early diffusion weighted imaging is an independent predictor for favorable outcome.

Extent of Hypoattenuation on CT Angiography Source Images in Basilar Artery Occlusion

The posterior circulation Acute Stroke Prognosis Early CT Score (pc-ASPECTS) quantifies the extent of early ischemic changes in the posterior circulation with a 10-point grading system. We hypothesized that pc-ASPECTS applied to CT angiography source images predicts functional outcome of patients in the Basilar Artery International Cooperation Study (BASICS). BASICS was a prospective, observational registry of consecutive patients with acute symptomatic basilar artery occlusion. Functional outcome was assessed at 1 month. We applied pc-ASPECTS to CT angiography source images of patients with CT angiography for confirmation of basilar artery occlusion. We calculated unadjusted and adjusted risk ratios (RRs) of pc-ASPECTS dichotomized at ≥8 versus <8. Primary outcome measure was favorable outcome (modified Rankin Scale scores 0-3). Secondary outcome measures were mortality and functional independence (modified Rankin Scale scores 0-2). Of 158 patients included, 78 patients had a CT angiography source images pc-ASPECTS≥8. Patients with a pc-ASPECTS≥8 more often had a favorable outcome than patients with a pc-ASPECTS<8 (crude RR, 1.7; 95% CI, 0.98-3.0). After adjustment for age, baseline National Institutes of Health Stroke Scale score, and thrombolysis, pc-ASPECTS≥8 was not related to favorable outcome (RR, 1.3; 95% CI, 0.8-2.2), but it was related to reduced mortality (RR, 0.7; 95% CI, 0.5-0.98) and functional independence (RR, 2.0; 95% CI, 1.1-3.8). In post hoc analysis, pc-ASPECTS dichotomized at ≥6 versus <6 predicted a favorable outcome (adjusted RR, 3.1; 95% CI, 1.2-7.5). pc-ASPECTS on CT angiography source images independently predicted death and functional independence at 1 month in the CT angiography subgroup of patients in the BASICS registry.

Thrombolysis in Posterior Circulation Stroke: Stroke Subtypes and Patterns, Complications and Outcome

Background: Patients with posterior circulation stroke (PCS) were underrepresented in or even excluded from the large clinical trials investigating acute therapy with thrombolysis. Therefore, the knowledge about potential benefits and risks of thrombolysis in PCS is sparse. Methods: From July 2004 until June 2007, 237 stroke patients were treated with thrombolysis within 3 h after onset of symptoms in our stroke unit. Baseline characteristics, etiology, CT/MRI stroke patterns, clinical outcome, and complications of patients with PCS were compared to those with anterior circulation stroke (ACS). Results: There were 30 patients in the PCS group; 198 had ACS. In the PCS group, less patients had a history of prior stroke (0/30 vs. 31/198 (15.7%), p = 0.02) and less were treated with platelet inhibitors (6/30 (20.0%) vs. 83/198 (41.9%), p = 0.02). Onset to treatment time was higher in the PCS group (156.2 ± 23.2 vs. 141.1 ± 30.7, p = 0.01). Small vessel disease occurred more often in PCS patients (10/30 (33.3%) vs. 12/198 (6.1%), p < 0.001), whereas stroke of undetermined cause was less frequent (5/30 (16.7%) vs. 75/198 (37.9%), p = 0.02). Correspondingly, PCS patients had more lacunar (13/30 (43.3%) vs. 15/198 (7.3%), p < 0.001) strokes on CT/MRI. Patients with PCS had significantly lower median NIHSS scores after 2 and 24 h, whereas the median NIHSS and mRS scores at discharge as well as the mRS score at the 3-month follow-up, although still lower, did not differ significantly between both groups. Outcome was similar with regard to complications and mortality. Conclusions: Patients with PCS have a higher rate of small vessel disease and lacunar stroke. In terms of potential benefits and risks of thrombolysis, we could demonstrate no significant differences between PCS and ACS. Acute PCS patients should be diagnosed and treated with the same elaborateness as ACS patients.

Ataxia in posterior circulation stroke: Clinical–MRI correlations

Objective Ataxia is characterized clinically by four signs (gait and limb ataxia, dysarthria and nystagmus). Although ataxia has been described in posterior circulation (PC) stroke series, there are no prospective studies that have investigated a possible differential role of the cerebellum or its input/outputs in causing ataxia. Methods Ataxia was semi-quantified according to the International Cooperative Ataxia Rating Scale (ICARS) in 92 consecutive patients with acute PC stroke. Four topographical patterns based on magnetic resonance imaging (MRI) findings were identified: picaCH pattern (posterior inferior cerebellar artery infarct); scaCH pattern (superior cerebellar artery infarct); CH/CP pattern (infarct involving both the cerebellum and the brainstem cerebellar pathways); and CP pattern (infarct involving the brainstem cerebellar pathways). Results Gait ataxia was present in 95.7%, limb ataxia in 76.1%, dysarthria in 56.5% and nystagmus in 65.2% of patients. Gait ataxia frequency did not differ between the patterns, but was significantly more severe in the CH/CP pattern than in either picaCH (P = 0.0059) or CP (P = 0.0065) pattern. Limb ataxia was significantly less frequent (P < 0.001) and less severe (P < 0.001) in picaCH pattern than other patterns. Dysarthria was less frequent in picaCH pattern than in other patterns (P = 0.018) and less severe than in scaCH (P = 0.0043) or CP (P = 0.0047) pattern. No differences in nystagmus frequency or severity were observed across all four patterns. Conclusion In PC stroke gait ataxia was almost always present, regardless of the lesion site. Limb ataxia and dysarthria were less frequent in the picaCH pattern, whereas nystagmus, when present, did not differ among the topographical patterns.

Hyperdense basilar artery sign diagnoses acute posterior circulation stroke and predicts short-term outcome

It is well established that the hyperdense middle cerebral artery sign is a specific marker for early ischemia in anterior circulation. However, little is known about the hyperdense basilar artery sign (HDBA) in posterior circulation. Our aim was to determine whether the HDBA sign has utility in early diagnosis of acute posterior circulation stroke and prediction of short-term outcome. Three-blinded readers examined unenhanced computed tomography scans for the HDBA sign, and materials were classified into two groups according to this sign. Vascular risk factors, admission and discharge National Institute of Health Stroke Scale (NIHSS) scores, short-term outcome, and radiological findings between the two groups were compared. One hundred and twenty-six cases of acute posterior circulation stroke (PCS) were included in the study. No statistically significant differences were found in risk factors of ischemic stroke, except atrial fibrillation (P=0.025). Admission and discharge NIHSS scores for the positive HDBA group were significantly higher than scores for the negative HDBA group (P=0.001, 0.002, respectively). The infarction territory for the positive HDBA group was mainly multi-region in nature (51.6%, P<0.001), while the negative HDBA group showed mainly middle territory infarction. Significant independent predictors of short-term outcome included the HDBA sign (P<0.001) and admission NIHSS scores (P<0.001). Approximately half of the HDBA patients showed multi-region infarction and a serious neurological symptom. Based on our results, this sign might not only be helpful in early diagnosis of acute PCS but also be able to correlate with a poor short-term outcome.

CT Angiography Source Images Predict Final Infarct Extent in Patients with Basilar Artery Occlusion

The posterior circulation Acute Stroke Prognosis Early CT Score (pc-ASPECTS) is a 10-point grading system to quantify ischemic changes in the posterior circulation. We analyzed whether pc-ASPECTS on CT angiography (CTA) source images (CTASI) predicted the final infarct extent and hemorrhagic transformation (HT) rate in patients with basilar artery occlusion. A pc-ASPECTS score of 10 indicates absence of visible ischemic changes in the posterior circulation, and pc-ASPECTS score of 0 indicates ischemic changes in the midbrain, pons, and bilateral thalami, posterior circulation territories, and cerebellar hemispheres. We retrospectively studied patients with basilar artery occlusion on CTA within 24 hours from symptom onset. We applied pc-ASPECTS to noncontrast CT (NCCT), CTASI, and follow-up images by 3-reader-consensus and assessed HT on follow-up images. We calculated Spearman correlation coefficients and performed linear regression analysis. Final infarct extent and HT rates were compared across dichotomized CTASI pc-ASPECTS groups (>/= 8 vs < 8). Among 43 patients, median (range) onset to CTA time was 5.0 hours (range, 0.7-24 hours). Pc-ASPECTS on CTASI (r = 0.75; P < .001) but not NCCT (r = 0.29; P = .063) correlated with pc-ASPECTS on follow-up scans. Linear regression demonstrated a significant positive relationship between pc-ASPECTS on CTASI and follow-up scans (R(2) = 0.58; P < 01). Median follow-up pc-ASPECTS was lower in patients with a CTASI pc-ASPECTS < 8 compared with patients with a CTASI pc-ASPECTS of 8 or more, respectively (P < .001). HT rates were 27.3% vs 9.5%, respectively (P = .24). None of 8 patients without thrombolysis had HT on follow-up scans. The extent of hypoattenuation on CTASI predicts the final infarct extent in patients with basilar artery occlusion.

Hyperdense Basilar Artery Sign on Unenhanced CT Predicts Thrombus and Outcome in Acute Posterior Circulation Stroke

In acute stroke patients, the presence of a hyperdense middle cerebral artery sign on unenhanced CT is a specific but insensitive indicator of acute thrombosis. Our purpose was to determine whether the hyperdense basilar artery (HDBA) sign has utility in detecting thrombosis and predicting outcome in patients presenting with signs and symptoms of posterior circulation stroke. Unenhanced CT scans obtained within 24 hours of symptom onset in 95 patients with suspected posterior circulation stroke were reviewed. Three neuroimagers blinded to clinical outcome and results of the concurrent CT angiography (which served as the reference standard) rated presence of HDBA sign on a 5-point scale for level of certainty (1=definitely absent; 5=definitely present). Receiver operating characteristic curve analysis was performed. Short-term outcome was measured by discharge National Institute of Health Stroke Scale (NIHSS) scores; long-term outcome was measured by 6-month modified Rankin score (dichotomized, poor outcome defined as modified Rankin score >2). The following variables were correlated with short-term and long-term outcome by univariate analysis: HDBA sign, age, sex, time from stroke onset to imaging, admission NIHSS, history of stroke/TIA, atrial fibrillation, coronary artery disease, hypertension, diabetes, hypercholesterolemia, tobacco use, and thrombolysis. Variables showing correlation with P<0.1 were included in multiple regression analysis. Using a level of certainty cutoff score of >/=4 (probable, definite), HDBA sign had 71% sensitivity, 98% specificity, 94% accuracy, 83% positive predictive value, and 95% negative predictive value for basilar artery occlusion. In univariate analysis, factors significantly correlated with discharge NIHSS were: admission NIHSS (P<0.0001; r=0.77), HDBA sign (P=0.01), and diabetes (P=0.02). Factors showing significant correlation or association with poor long-term outcome were age (P=0.02), admission NIHSS (P=0.007), HDBA sign (P=0.02), and history of stroke or TIA (P=0.007). The odds ratio of HDBA sign for predicting poor long-term outcome was 5.3 (95% CI, 1.1-33.3). In multiple regression analysis, the only independent predictors of discharge NIHSS were admission NIHSS (P<0.0001) and HDBA sign (P=0.004). Significant independent predictors of poor long-term outcome were age (P=0.02), admission NIHSS (P=0.008), history of stroke/TIA (P=0.03), and HDBA sign (P=0.05). In patients presenting with a high pretest probability of posterior circulation stroke based on clinical symptoms, the presence of the HDBA sign on unenhanced CT is a strong predictor of basilar artery thrombosis, and both short- and long-term outcome.

Extent of Hypoattenuation on CT Angiography Source Images Predicts Functional Outcome in Patients With Basilar Artery Occlusion

Quantification of early ischemic changes (EIC) may predict functional outcome in patients with basilar artery occlusion (BAO). We tested the validity of a novel CT score, the posterior circulation Acute Stroke Prognosis Early CT score (pc-ASPECTS). Pc-ASPECTS allots the posterior circulation 10 points. Two points each are subtracted for EIC in midbrain or pons and 1 point each for EIC in left or right thalamus, cerebellum or PCA-territory, respectively. We studied 2 different populations: (1) patients with suspected vertebrobasilar ischemia and (2) patients with BAO. We applied pc-ASPECTS to noncontrast CT (NCCT), CT angiography source images (CTASI), and follow-up image by 3-reader consensus. We calculated sensitivity for ischemic changes and analyzed the predictivity of pc-ASPECTS for independent (modified Rankin Scale [mRS] score </=2) and favorable (mRS score </=3) outcome. Of 130 patients with suspected vertebrobasilar ischemia, 72% (94) had posterior circulation stroke, 8% (10) transient ischemic attack, and 20% (26) nonischemic etiology. Sensitivity for ischemic changes was improved with CTASI compared to NCCT (65% [95% CI, 57% to 73%] versus 46% [95% CI, 37% to 55%], respectively). Pc-ASPECTS score on CTASI but not NCCT predicted functional independence (OR 1.58; P=0.005 versus 1.22; P=0.42, respectively). Of 46 patients with BAO, 52% (12/23) with CTASI pc-ASPECTS score >/=8 but only 4% (1/23) with a score <8 had favorable functional outcome (RR 12.1; 95% CI, 1.7 to 84.9). This difference was consistent in 21 patients with angiographic recanalization (RR 7.7; 95% CI, 1.1 to 52.1). The CTASI pc-ASPECTS score may identify BAO patients unlikely to have a favorable outcome despite recanalization.

Current Issues in the Treatment of Acute Posterior Circulation Stroke

This article presents a narrative review of the non-medical, medical and endovascular aspects of the management of acute ischaemic stroke in the posterior circulation, a potentially devastating condition with high mortality and substantial disability in many of those who survive. Optimal management requires a combination of supportive measures and specific interventions and is best delivered within a high-dependency or intensive care environment. Non-medical measures include management of physiological parameters, respiratory support where necessary and prompt treatment of complications such as the development of hydrocephalus. Deterioration in conscious state and progression of symptoms may occur some time after initial presentation and after admission to hospital; when such progression is detected, very rapid therapeutic reperfusion may be feasible. Reperfusion strategies include intravenous and intra-arterial thrombolysis (IAT) and mechanical methods to aid reperfusion, including the use of mechanical clot disruption, clot retrieval or stenting devices. The optimal reperfusion strategy, including considerations of whether to use intravenous or intra-arterial thrombolytic approaches, the use of bridging intravenous treatment prior to intra-arterial treatment, and the use of pharmacological or mechanical adjuncts to IAT is not known. However, it seems likely that the important determinant of therapeutic efficacy is the speed and safety with which reperfusion can be achieved. It may also be that the time available to achieve reperfusion is longer than in the anterior circulation.

Mesencephalic and associated posterior circulation infarcts.

The purposes of this study were to evaluate and review the risk factors and clinical features of patients with posterior circulation stroke involving mesencephalon and neighboring structures and to describe the clinical syndromes according to the mesencephalic arterial territory involved. We studied all patients with acute posterior circulation stroke involving mesencephalon who were admitted consecutively to our stroke unit over a 6-year period. We selected these patients (3%) from 1296 patients with posterior circulation infarct. Neurological and radiological investigations, including MRI and angiography, were performed in all cases. We classified patients into 4 groups on the basis of MRI findings: (1) isolated mesencephalic infarcts (9 patients); (2) distal territory infarcts (19 patients), including mesencephalon, thalamus, medial temporal and occipital lobes, and cerebellum; (3) middle territory infarcts (12 patients), including the pons and anterior inferior cerebellar artery territory; and (4) proximal territory infarcts (1 patient), including the medulla and posterior inferior cerebellar artery territory. Middle mesencephalon involvement was the most common in all groups, and the anteromedial territory was frequently affected, depending on the direct perforators of basilar artery. In patients with isolated mesencephalic infarct, the clinical picture was dominated by nuclear or fascicular third-nerve palsy and contralateral motor deficits. The distal territory involvement was the most common and associated with consciousness disturbances, gait ataxia, ocular motor disturbances, and visual field deficits. The neurological picture of middle territory infarcts was dominated by consciousness disturbances with dysarthria, horizontal ocular motor disorders, and hemiparesis. Proximal territory involvement was rare and associated with acute unsteadiness, vertigo, dysphagia, dysphonia, tetra-ataxia, and motor weakness. The most common cause of stroke was large-artery disease in 16 patients (39%), cardioembolism in 8 (20%), and small-artery disease with lacunar mesencephalic infarct in 10 (24%). Bilateral mesencephalic infarcts were not uncommon (27%), mainly in patients with multiple and extended infarcts in the posterior circulation, and were associated with poor outcome compared with unilateral infarct. Our study highlights the topographic and clinical heterogeneity of the acute posterior circulation infarcts involving mesencephalon. The variety of the underlying potential causes of stroke requires detailed investigations of the extra and intracranial arteries and the heart.