Magnetic resonance imaging and clinical patterns of patients with 'spectacular shrinking deficit' after acute middle cerebral artery stroke

BACKGROUND: Rapid resolution of neurological deficits after severe middle cerebral artery (MCA) stroke has been coined spectacular shrinking deficit (SSD). We studied clinical and MRI patterns in patients with SSD. METHODS: Patients with acute MCA stroke <6 h were examined by stroke MRI (perfusion- and diffusion-weighted imaging (PWI, DWI), MR angiography (MRA)) at admission, day 1 and day 7. SSD was defined as a > or =8-point-reduction of neurological deficit in the National Institute of Health Stroke Scale (NIHSS) to a score of < or =4 within 24 h. PWI and DWI lesion volumes were measured on ADC (ADC < 80%) and time to peak maps (TTP > +4 s). Recanalization was assessed by MRA after 24 h. Final infarct volumes were defined on T2 weighted images at day seven. Outcome was assessed after 90 days using modified Rankin Scale (mRS) and Barthel Index (BI). RESULTS: SSD was present in 14 of 104 patients. Initial DWI and PWI lesion volumes were smaller in SSD patients - ADC < 80%: 8.9 (4.3-20.5) vs. 30 (0-266.7) ml; TTP > +4 s: 91.6 (29.7-205.8) vs. 131.5 (0-311.5) ml. Early recanalization was associated with SSD resulted in smaller final infarct volumes (11.9 (2.4-25.9) vs. 47.7 (1.2-288.5)). All SSD patients were independent at day 90 (mRS 0 (0-2); BI 100). CONCLUSION: The clinical syndrome of SSD is reflected by a typical MRI pattern with small initial DWI and PWI lesion volumes, timely recanalization and small final infarct volumes.     

Assessing the outcome of stroke: a comparison between MRI and clinical stroke scales

OBJECTIVES: To assess the correlation of diffusion-weighted (DWI) and perfusion-weighted imaging (PWI) findings with the severity of acute neurologic deficit and their ability to predict short and long-term clinical outcomes of stroke. The ability of DWI and PWI to predict the outcome was compared with the ability of clinical stroke scales to predict the outcome. METHODS: Forty-eight patients with acute stroke underwent diffusion DWI and PWI on the first and eighth day after the ictus. Clinical and functional scales were carried out before each scan and 3 months after the stroke. RESULTS: The volumes of both the DWI and the PWI lesions correlated well with the acute neurologic deficit and the final outcome. The first day PWI (r = 0.64) and the National Institutes of Health Stroke Scale (NIHSS) scores (r = 0.70) correlated well with the final outcome. However, in logistic regression analysis, only the NIHSS score at the acute stage was the only independent predictor of the long-term clinical outcome. CONCLUSION: While the PWI and DWI lesion volumes correlated well with the outcome of the stroke, the imaging measurements did not improve the prognostic power over plain clinical stroke scale scores.     

Monitoring intravenous recombinant tissue plasminogen activator thrombolysis for acute ischemic stroke with diffusion and perfusion MRI

BACKGROUND AND PURPOSE: Intravenous recombinant tissue plasminogen activator (rtPA) administration is an effective therapy for ischemic stroke when initiated within 3 hours and possibly up to 6 hours after symptom onset. To improve patient selection, a fast diagnostic tool that allows reliable diagnosis of hemorrhage and ischemia, vessel status, and tissue at risk at an early stage may be useful. We studied the feasibility of stroke MRI for the initial evaluation and follow-up monitoring of patients undergoing intravenous thrombolysis. METHODS: Stroke MRI (diffusion- and perfusion-weighted imaging [DWI and PWI, respectively], magnetic resonance angiography, and T2-weighted imaging) was performed before, during, or after thrombolysis and on days 2 and 5. We assessed clinical scores (National Institutes of Health Stroke Scale [NIHSS], Scandinavian Stroke Scale [SSS], Barthel Index, and Rankin scale) at days 1, 2, 5, 30, and 90. Furthermore, we performed volumetric analysis of infarct volumes on days 1, 2, and 5 as shown in PWI, DWI, and T2-weighted imaging. RESULTS: Twenty-four patients received rtPA within a mean time interval after symptom onset of 3.27 hours and stroke MRI of 3.43 hours. Vessel occlusion was present in 20 of 24 patients; 11 vessels recanalized (group 1), and 9 did not (group 2). The baseline PWI lesion volume was significantly larger (P=0.008) than outcome lesion size in group 1, whereas baseline DWI lesion volume was significantly smaller (P=0.008) than final infarct size in group 2. Intergroup outcome differed significantly for all scores at days 30 and 90 (all P<0.01). Intragroup differences were significant in group 1 for change in SSS and NIHSS between day 1 and day 30 (P=0.003) and for SSS only between day 1 and day 90 (P=0.004). CONCLUSIONS: Stroke MRI provides comprehensive prognostically relevant information regarding the brain in hyperacute stroke. Stroke MRI may be used as a single imaging tool in acute stroke to identify and monitor candidates for thrombolysis. It is proposed that stroke MRI is safe, reliable, and cost effective; however, our data do not prove this assumption. Early recanalization achieved by thrombolysis can save tissue at risk if present and may result in significantly smaller infarcts and a significantly better outcome.     

Combined diffusion and perfusion MRI with correlation to single-photon emission CT in acute ischemic stroke. Ischemic penumbra predicts infarct growth.

BACKGROUND AND PURPOSE: More effective imaging methods are needed to overcome the limitations of CT in the investigation of treatments for acute ischemic stroke. Diffusion-weighted MRI (DWI) is sensitive in detecting infarcted brain tissue, whereas perfusion-weighted MRI (PWI) can detect brain perfusion in the same imaging session. Combining these methods may help in identifying the ischemic penumbra, which is an important concept in the hemodynamics of acute stroke. The purpose of this study was to determine whether combined DWI and PWI in acute (<24 hours) ischemic stroke can predict infarct growth and final size. METHODS: Forty-six patients with acute ischemic stroke underwent DWI and PWI on days 1, 2, and 8. No patient received thrombolysis. Twenty-three patients underwent single-photon emission CT in the acute phase. Lesion volumes were measured from DWI, SPECT, and maps of relative cerebral blood flow calculated from PWI. RESULTS: The mean volume of infarcted tissue detected by DWI increased from 46.1 to 75.6 cm(3) between days 1 and 2 (P<0.001; n=46) and to 78.5 cm(3) after 1 week (P<0.001; n=42). The perfusion-diffusion mismatch correlated with infarct growth (r=0. 699, P<0.001). The volume of hypoperfusion on the initial PWI correlated with final infarct size (r=0.827, P<0.001). The hypoperfusion volumes detected by PWI and SPECT correlated significantly (r=0.824, P<0.001). CONCLUSIONS: Combined DWI and PWI can predict infarct enlargement in acute stroke. PWI can detect hypoperfused brain tissue in good agreement with SPECT in acute stroke.     

Prediction of hemorrhagic transformation following acute stroke: role of diffusion- and perfusion-weighted magnetic resonance imaging

BACKGROUND: Acute diffusion-weighted (DWI) and perfusion-weighted (PWI) magnetic resonance imaging (MRI) findings may correlate with secondary hemorrhagic transformation (HT) risk in patients with stroke. This information could be of value, particularly in individuals being considered for thrombolytic therapy. OBJECTIVE: To determine the relationship between DWI and PWI findings and the risk of secondary HT in patients with acute stroke. DESIGN: Retrospective case series. SETTING: Academic medical center. PATIENTS: Twenty-seven patients with acute stroke capable of being evaluated with DWI/PWI 8 hours or less after symptom onset. MAIN OUTCOME MEASURES: Apparent diffusion coefficient values, perfusion delay measurements, and subsequent MRI or computed tomographic scans detected HT. RESULTS: The mean +/- SD apparent diffusion coefficient of ischemic regions that experienced HT was significantly lower than the overall mean +/- SD apparent diffusion coefficient of all ischemic areas analyzed (0.510 +/- 0.140 x 10(-3) mm(2)/s vs 623 +/- 0.113 x 10(-3) mm(2)/s; P =.004). This difference remained significant when comparing the HT-destined ischemic areas with the non-HT-destined areas within the same ischemic lesion (P =.02). Patients receiving recombinant tissue-type plasminogen activator (rt-PA) experienced HT significantly earlier than patients not receiving rt-PA (P =.002). Moreover, a persistent perfusion deficit in the area of subsequent hemorrhage at 3 to 6 hours after the initial MRI scan was identified in significantly more patients who experienced HT than in those who did not (83% vs 30%; P =.03). CONCLUSION: Both DWI and PWI scans detect abnormalities that are associated with HT. These findings support a role for MRI in identifying patients who are at increased risk for secondary HT following acute ischemic stroke.     

Diffusion- and perfusion-weighted MRI. The DWI/PWI mismatch region in acute stroke.

BACKGROUND AND PURPOSE: Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) are relatively new MR techniques increasingly used in acute stroke. During the first hours of stroke evolution, the regions with abnormal perfusion are typically larger than the DWI lesions, and this mismatch region has been suggested to be "tissue at risk." The aim of this study was to evaluate the PWI/DWI mismatch region in acute stroke patients and find parameters indicative of both infarct progression and functional impairment. METHODS: Twenty patients with nonlacunar ischemic stroke were imaged with DWI, PWI, and conventional MRI within 24 hours of symptom onset and after 1 week; in addition, the European Stroke Scale (ESS) score was recorded. With PWI, the volumes of regions with "time-to-peak" (TTP) delays of >/=2, 4, 6, 8, and 10 seconds were measured; these volumes were compared with the acute DWI lesion volumes, final infarct size, and ESS score. RESULTS: In 80% of patients the acute DWI lesion was surrounded by regions with abnormal TTP delays (PWI>DWI lesion). A TTP delay of >/=6 s in the mismatch region was found to be associated with lesion enlargement between the initial and follow-up MRI scans. Lesions increased in 9 of 12 patients (75%) in whom the area with TTP delay >/=6 s was larger than the DWI lesion, but they increased in only 1 of 8 (12.5%) of the remaining patients, in whom the area with a TTP delay >/=6 s was smaller than the DWI lesion. The volume of the regions with TTP delays of >/=4 s correlated better with ESS (r=-0.88, P<0.001) than other PWI (or DWI) volumes, which indicated that a TTP delay of approximately 4 s might be the threshold for functional impairment of brain tissue. CONCLUSIONS: Only patients with severe perfusion deficits in the PWI/DWI mismatch (TTP delays of >/=6 s) are at high risk of lesion enlargement. Functionally, more moderate perfusion deficits (TTP delays >/=4 and <6 s) appear to also contribute to the acute clinical deficit.     

Influence of pretreatment MRI parameters on clinical outcome, recanalization and infarct size in 49 stroke patients treated by intravenous tissue plasminogen activator

We hypothesized that pretreatment magnetic resonance imaging (MRI) parameters might predict clinical outcome, recanalization and final infarct size in acute ischemic stroke patients treated by intravenous recombinant tissue plasminogen activator (rt-PA). MRI was performed prior to thrombolysis and at day 1 with the following sequences: magnetic resonance angiography (MRA), T2*-gradient echo (GE) imaging, diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI). Final infarct size was assessed at day 60 by T2-weighted imaging (T2-WI). The National Institutes of Health Stroke Scale (NIHSS) score was assessed prior to rt-PA therapy and the modified Rankin Scale (m-RS) score was assessed at day 60. A poor outcome was defined as a day 60 m-RS score >2. Univariate and multivariate logistic regression analyses were used to identify the predictors of clinical outcome, recanalization and infarct size. Forty-nine patients fulfilled the inclusion criteria. Baseline NIHSS score was the best independent indicator of clinical outcome (p=0.002). A worse clinical outcome was observed in patients with tandem internal carotid artery (ICA)+middle cerebral artery (MCA) occlusion versus other sites of arterial occlusion (p=0.009), and in patients with larger pretreatment PWI (p=0.001) and DWI (p=0.01) lesion volumes. Two factors predict a low rate of recanalization: a proximal site of arterial occlusion (p=0.02) and a delayed time to peak (TTP) on pretreatment PWI (p=0.05). The final infarct size was correlated with pretreatment DWI lesion volume (p=0.025). Recanalization was associated with a lower final infarct size (p=0.003). In conclusion, a severe baseline NIHSS score, a critical level of pretreatment DWI/PWI parameters and a proximal site of occlusion are predictive of a worse outcome after IV rt-PA for acute ischemic stroke.     

Relationship between severity of MR perfusion deficit and DWI lesion evolution

OBJECTIVE: To assess whether a quantitative analysis of the severity of the early perfusion deficit on MRI in acute ischemic stroke predicts the evolution of the perfusion/diffusion mismatch and to determine thresholds of hypoperfusion that can distinguish between critical and noncritical hypoperfusion. METHODS: Patients with acute ischemic stroke were studied in whom perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI MRI) were performed within 7 hours of symptom onset and again after 4 to 7 days. Patients with early important decreases in points on the NIH Stroke Scale were excluded. Maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were created. These hemodynamic parameters were correlated with the degree of recruitment of the baseline PWI lesion by the DWI lesion. RESULTS: Twelve patients had an initial PWI > DWI mismatch of >20%. A linear relationship was observed between the initial MTT and the degree of recruitment of the baseline PWI lesion by the DWI lesion at follow-up (R(2) = 0.9, p < 0.001). Higher CBV values were associated with higher degrees of recruitment (rho = 0.732, p < 0.007). The volume of MTT of >4 (R(2) = 0.86, p < 0.001) or >6 seconds (R(2) = 0.85, p < 0.001) predicted final infarct size. CONCLUSION: Among patients who have had an acute stroke with PWI > DWI, who do not have dramatic early clinical improvement, the degree of expansion of the initial DWI lesion correlates with the severity of the initial perfusion deficit as measured by the mean transit time and the cerebral blood volume.     

Clinical and imaging predictors of intracerebral haemorrhage in stroke patients treated with intravenous tissue plasminogen activator

OBJECTIVE: To evaluate clinical, biological, and pretreatment imaging variables for predictors of tissue plasminogen activator (tPA) related intracerebral haemorrhage (ICH) in stroke patients. METHODS: 48 consecutive patients with hemispheric stroke were given intravenous tPA within seven hours of symptom onset, after computed tomography (CT) and magnetic resonance imaging (MRI) of the brain. Baseline diffusion weighted (DWI) and perfusion weighted (PWI) imaging volumes, time to peak, mean transit time, regional cerebral blood flow index, and regional cerebral blood volume were evaluated. The distribution of apparent diffusion coefficient (ADC) values was determined within each DWI lesion. RESULTS: The symptomatic ICH rate was 8.3% (four of 48); the rate for any ICH was 43.8% (21 of 48). Univariate analysis showed that age, weight, history of hyperlipidaemia, baseline NIHSS score, glucose level, red blood cell count, and lacunar state on MRI were associated with ICH. However, mean 24 hour systolic blood pressure and a hyperdense artery sign on pretreatment CT were the only independent predictors of ICH. Patients with a hyperdense artery sign had larger pretreatment PWI and DWI lesion volumes and a higher NIHSS score. Analysis of the distribution of ADC values within DWI lesions showed that a greater percentage of pixels had lower ADCs (< 400 x 10(-6) mm(2)/s) in patients who experienced ICH than in those who did not. CONCLUSION: Key clinical and biological variables, pretreatment CT signs, and MRI indices are associated with tPA related intracerebral haemorrhage.     

Stroke magnetic resonance imaging within 6 hours after onset of hyperacute cerebral ischemia

We studied the diagnostic and prognostic value of diffusion- and perfusion-weighted magnetic resonancce imaging (DWI and PWI) for the initial evaluation and follow-up monitoring of patients with stroke that had ensued less than 6 hours previously. Further, we examined the role of vessel patency or occlusion and subsequent recanalization or persistent occlusion for further clinical and morphological stroke progression so as to define categories of patients and facilitate treatment decisions. Fifty-one patients underwent stroke magnetic resonance imaging (DWI, PWI, magnetic resonance angiography, and T2-weighted imaging) within 3.3 +/- 1.29 hours, and, of those, 41 underwent follow-up magnetic resonance imaging on day 2 and 28 on day 5. In addition, we assessed clinical scores (on the National Institutes of Health Stroke Scale, Scandinavian Stroke Scale, Barthel Index, and Modified Rankin Scale) on days 1, 2, 5, 30, and 90 and performed volumetric analysis of lesion volumes. In all, 25 patients had a proximal, 18 a distal, and 8 no vessel occlusion. Furthermore, 15 of 43 patients exhibited recanalization on day 2. Vessel occlusion was associated with a PWI-DWI mismatch on the initial magnetic resonance imaging, vessel patency with a PWI-DWI match (p < 0.0001). Outcome scores and lesion volumes differed significantly between patients experiencing recanalization and those who did not (all p < 0.0001). Acute DWI and PWI lesion volumes correlated poorly with acute clinical scores and only modestly with outcome scores. We have concluded on the basis of this study that early recanalization saves tissue at risk of ischemic infarction and results in significantly smaller infarcts and a significantly better clinical outcome. Patients with proximal vessel occlusions have a larger amount of tissue at risk, a lower recanalization rate, and a worse outcome. Urgent recanalization seems to be of utmost importance for these patients.     

Early magnetic resonance imaging prediction of arterial recanalization and late infarct volume in acute carotid artery stroke.

In patients with acute ischemic stroke, early recanalization may save tissue at risk for ischemic infarction, thus resulting in smaller infarcts and better clinical outcome. The hypothesis that clinical and diffusion- and perfusion-weighted imaging (DWI, PWI) parameters may have a predictive value for early recanalization and final infarct size was assessed. Twenty-nine patients were prospectively enrolled and underwent sequential magnetic resonance imaging (1) within 6 hours from hemispheric stroke onset, before thrombolytic therapy; (2) at day 1; and (3) at day 60. Late infarct volume was assessed by T2 -weighted imaging. At each time, clinical status was assessed by the National Institutes of Health Stroke Scale (NIHSS). Twenty-eight patients had arterial occlusion at day 0 magnetic resonance angiography (MRA). They were classified into two groups according to day 1 MRA: recanalization (n = 18) versus persistent occlusion (n = 10). Any significant differences between these groups were assessed regarding (1) PWI and DWI abnormality volumes, (2) relative and absolute time-to-peak (TTP) and apparent diffusion coefficient within the lesion on DWI; and (3) day 60 lesion volume on T2 -weighted imaging. Univariate and multivariate logistic regression analysis showed that the most powerful predictive factors for recanalization were lower baseline NIHSS score and lower baseline absolute TTP within the lesion on DWI. The best predictors of late infarct size were day 0 lesion volume on DWI and day 1 recanalization. Early PWI and DWI studies and day 1 MRA provide relevant predictive information on stroke outcome.     

Correlation between diffusion- and perfusion-weighted MRI and neurological deficit measured by the Scandinavian Stroke Scale and Barthel Index in hyperacute subcortical stroke (< or = 6 hours)

OBJECTIVE: We used combined diffusion-weighted (DWI) and perfusion-weighted (PWI) MRI to characterize hyperacute infarctions within 6 h of symptom onset with special reference to subcortical infarctions, and investigated the relation between perfusion-diffusion mismatch volume and functional outcome. MATERIAL AND METHODS: Twenty-two patients presenting with symptoms of acute stroke underwent DWI and PWI within 6 h of symptom onset, and follow-up MRI 30 days later. Twelve of these had a subcortical infarction on acute DWI. Lesion volumes were measured by acute DWI and PWI as well as chronic T(2)-weighted MRI (T2WI). Clinical severity was measured by the Scandinavian Stroke Scale (SSS) and the Barthel Index (BI). RESULTS: In the 12 patients with subcortical infarctions, PWI and especially DWI correlated strongly with acute and chronic neurological SSS score, as well as with final infarct volume. Furthermore, a hyperacute PWI/DWI mismatch in this subgroup predicted lesion growth. There was a weaker correlation between acute DWI/PWI and neurological score among all 22 patients, and patients with a PWI/DWI mismatch larger than 100 ml had a significantly larger lesion growth and a poorer outcome than patients with a smaller mismatch. CONCLUSIONS: Subcortical infarctions may represent a sizeable subgroup of acute stroke patients. Also subcortical infarctions may have a PWI/DWI mismatch and therefore may respond to neuroprotective/thrombolytic therapy. Hyperacute DWI may reflect the acute clinical status and predict the outcome in patients with subcortical infarction.     

Association of higher serum calcium levels with smaller infarct volumes in acute ischemic stroke

BACKGROUND: Elevated serum calcium levels at admission in patients with stroke have been associated with less severe clinical deficits and with better outcomes; however, the relationship between serum calcium levels and volumetric measurement of cerebral infarct size on neuroimaging has not been studied, to our knowledge. OBJECTIVE: To assess the relationship between serum calcium levels at admission and initial diffusion-weighted magnetic resonance imaging (DWI) infarct volumes among patients with acute ischemic stroke. DESIGN: Secondary analysis of prospectively collected hospital quality improvement data. SETTING: Tertiary university hospital. PATIENTS: One hundred seventy-three consecutive patients with acute ischemic stroke initially seen within 24 hours of the last known well time. MAIN OUTCOME MEASURES: Total serum calcium levels were measured on admission and were collapsed into quartiles. The DWI lesions were outlined using a semiautomated threshold technique. The relationship between serum calcium level quartiles and DWI infarct volumes was examined using multivariate quartile regression analysis. RESULTS: One hundred seventy-three patients (mean age, 70.3 years [age range, 24-100 years]; median National Institutes of Health Stroke Scale score, 4 [range, 0-38]) met the study criteria. The median DWI infarct volumes for the serum calcium level quartiles (lowest to highest quartile) were 9.42, 2.11, 1.03, and 3.68 mL. The median DWI infarct volume in the lowest serum calcium level quartile was larger than that in the other 3 quartiles (P < .005). After multivariate analysis, the median adjusted DWI infarct volumes for the serum calcium level quartiles (lowest to highest) were 8.9, 5.8, 4.5, and 3.8 mL. The median adjusted DWI infarct volume in the lowest serum calcium level quartile was statistically significantly larger than that in the other 3 quartiles (P < .05). CONCLUSIONS: Higher serum calcium levels at admission are associated with smaller cerebral infarct volumes among patients with acute ischemic stroke. These results suggest that serum calcium level may serve as a clinical prognosticator following stroke and may be a potential therapeutic target for improving stroke outcome.     

表观弥散系数对确定急性缺血性卒中缺血半暗带的潜在价值

目的 探讨表观弥散系数（apparent diffusion coefficient,ADC）对确定急性缺血性卒中缺血半暗带的潜在价值。 方法 选择发病9 h内完成多模式磁共振成像（magnetic resonance imaging,MRI）检查的前循环急性缺血性卒中患者49例。应用自制软件进行灌注加权像（perfusion-weighted imaging,PWI）和弥散加权像（diffusion-weighted imaging,DWI）异常区域的体积测量。缺血半暗带以PWI/DWI错配表示。同时采用全自动图像分析系统,以DWI图像计算得到的ADC图作为输入数据,来判断缺血半暗带的存在（以下简称为ADC方法）,然后比较这两种方法在判断缺血半暗带方面的差异。 结果 入选的49例患者中,存在PWI/DWI错配者为43例,符合ADC方法判断缺血半暗带标准者有41例。这两种方法在判断是否存在缺血半暗带的结果中有41例相符,对判断缺血半暗带的差异无统计学意义（P>0.05）。ADC方法判断缺血半暗带的敏感度为88.4%、特异度为50.0%。 结论 由于不需做PWI检查,ADC方法对确定缺血半暗带具有潜在的临床实用价值,有可能成为一种简便易行的确定缺血半暗带的方法。     

Normobaric hyperoxia reduces MRI diffusion abnormalities and infarct size in experimental stroke

BACKGROUND: Hyperbaric oxygen therapy is considered an important stroke treatment strategy. BACKGROUND: To determine whether normobaric oxygen is neuroprotective, and, if so, what the therapeutic time window is. METHODS: Experiment 1-Serial diffusion- and perfusion-weighted MRI (DWI and PWI) was performed after middle cerebral artery filament occlusion (MCAO) in rats randomized to FiO(2) 30% (normoxia) or FiO(2) 100% (hyperoxia). Experiment 2-48-hour lesion volumes were analyzed in rats subjected to 2-hour MCAO and randomized to normoxia or hyperoxia starting 15, 30, or 45 minutes after MCAO and ending 15 minutes after reperfusion. RESULTS: Experiment 1-Lesion apparent diffusion coefficient (ADC) values were persistently low in normoxic animals. In hyperoxia-treated rats, ADC values in cortical border zones showed progressive recovery from 66 +/- 3% of contralateral before hyperoxia, to 104 +/- 20% at approximately 2 hours. Striatal ADC values showed early but ill-sustained improvement. ADC lesion volumes increased progressively in the normoxia group. In the hyperoxia group, ADC lesion volumes tended to decrease after starting hyperoxia; however, lesions later increased in size, and 2-hour lesion volumes were not significantly different from baseline. PWI showed stable right MCA hypoperfusion in all animals. Experiment 2-Hyperoxia within 30 minutes significantly reduced total and cortical lesion volumes at 48 hours after stroke. Striatal lesion volumes were significantly reduced in the hyperoxia-15 group. CONCLUSION: In rats subjected to transient stroke, 100% oxygen administered within 30 minutes salvages ischemic brain tissue, especially in the cerebral cortex. Reducing the time to treatment enhances the degree of neuroprotection.     

Spectacular shrinking deficit: insights from multimodal magnetic resonance imaging after embolic middle cerebral artery occlusion in Sprague-Dawley rats.

Almost no data is available on the serial changes in the brain after spectacular shrinking deficit (SSD) that may help understand this relatively rare clinical phenomenon. Quantitative diffusion-(DWI), perfusion-(PWI), T(1)-(T1WI), T(2)-weighted (T2WI), and functional magnetic resonance imaging (fMRI) were performed before, during, and up to 7 days after embolic middle cerebral artery occlusion (eMCAO) in male Sprague-Dawley rats (n=9). Region of interest (ROI) analysis was used to evaluate structural and functional MR signal changes within three ROIs defined by the apparent diffusion coefficient (ADC), cerebral blood flow (CBF) signatures, and final tissue viability. DWI, PWI, and T2WI lesion volumes were calculated using previously established viability thresholds and final infarct volumes ascertained with 2,3,5-triphenyltetrazolium chloride (TTC) staining. Serial MRI demonstrated spontaneous reperfusion of initially hypoperfused MCA regions accompanied by substantial reduction of initial ADC and CBF lesions and gradual recovery of neurological outcome. Recovery rates of CBF/ADC abnormalities differed among ROIs. Functional magnetic resonance imaging showed persistent tissue dysfunction after the recovery of the CBF/ADC lesions. This study may facilitate our understanding of the pathophysiological mechanisms by which early, spontaneous reperfusion affects tissue fate and neurological function.     

Differential patterns of evolution in acute middle cerebral artery infarction with perfusion-diffusion mismatch: atherosclerotic vs. cardioembolic occlusion

BACKGROUND: An acute perfusion-diffusion mismatch is known to be the strongest predictor of infarct growth. However, the differential patterns of clinical and radiological evolution according to stroke mechanism are unknown. METHODS: The study retrospectively reviewed consecutive patients who had 1) acute middle cerebral artery (MCA) territory infarction, 2) diffusion- and perfusion-weighted imaging (DWI and PWI) and MR angiography within 24 h of onset, and follow-up DWI 5 days later, 3) stenosis (>/=50%) or occlusion of MCA on baseline imaging, 4) a baseline PWI-DWI mismatch >20%, and 5) either atherosclerotic MCA disease (MCAD) or cardioembolism (CE). National Institutes of Health Stroke Scale (NIHSS) scores and infarct volume at baseline and 5 days were obtained. RESULTS: Of 90 patients, 52 had MCAD and 38 had CE. At baseline, CE group had more severe stroke (median NIHSS, 9 vs. 5; p=0.001) and larger infarct volume (median 8.32 cc vs. 3.0 cc; p=0.034) than MCAD group. During the 1-week period, CE group had larger infarct volume growth (median 12.85 cc vs. 3.02 cc; p=0.004) than MCAD group, although clinical improvement based on NIHSS (baseline minus 5-day) tended to be higher for CE than MCAD group (median 3 vs. 1; p=0.08). The correlation between infarct volume and NIHSS score was stronger in CE (r=0.841) compared to MCAD (r=0.582) group at 5-day. CONCLUSIONS: Substantial differences in the clinico-radiological evolution of acute ischemic stroke exist according to stroke mechanism. These data emphasize the importance of the stroke mechanism in the design of MRI-based acute stroke trials.     

Etiology of Perfusion-Diffusion Magnetic Resonance Imaging Mismatch Patterns

BACKGROUND AND PURPOSE: Diffusion-and perfusion-weighted magnetic resonance imaging (DWI and PWI) are useful tools for the assessment of brain ischemia. Discrepancies between the extent of DWI and PWI abnormalities are thought to depend pre dominantly on time from symptom onset to magnetic resonance imaging (MRI) examination. However, underlying ischemic stroke etiology can also be important. A mismatch may indicate the presence of tissue at risk for infarction, whereas the relevance of other DWI/PWI patterns is uncertain. The authors therefore investigated the etiology of brain ischemia in patients with different DWI/PWI patterns. METHODS: Retrospective study of 130 patients with acute brain ischemia and detailed stroke workup, including MRI within a week after symptom onset (40 +/- 39 hours). Patients were divided into the following groups: mis-match (PWI > DWI), reverse mismatch (DWI > PWI), and match (<25% difference between PWI and DWI). RESULTS: Mismatch occurred in 49% of patients, whereas 22% had reverse mis-match and 29% matched lesions. Time from symptom onset to MRI examination was similar between the 3 groups. Largeartery atherosclerosis increased by almost 4-fold the odds of mismatch (odds ratio: 3.89, 95% confidence interval: 1.72-8.78; P < .001), whereas patients with reverse mismatch were likely to have cryptogenic stroke. Patients with matched lesions were similarly distributed among different stroke subtypes. CONCLUSIONS: Ischemic stroke etiology appears to influence the development of specific DWI/PWI patterns. Prospective studies are needed to confirm these observations.     

Characterizing the diffusion/perfusion mismatch in experimental focal cerebral ischemia

Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) can rapidly detect lesions in acute ischemic stroke patients. The PWI volume is typically substantially larger than the DWI volume shortly after onset, that is, a diffusion/ perfusion mismatch. The aims of this study were to follow the evolution of the diffusion/ perfusion mismatch in permanent and 60- minute temporary focal experimental ischemia models in Sprague-Dawley rats using the intraluminal middle cerebral artery occlusion (MCAO) method. DWI and arterial spin-labeled PWI were performed at 30, 60, 90, 120, and 180 minutes after occlusion and lesion volumes (mm(3)) calculated At 24 hours after MCAO, and infarct volume was determined using triphenyltetrazolium chloride staining. In the permanent MCAO group, the lesion volume on the ADC maps was significantly smaller than that on the cerebral blood flow maps through the first 60 minutes after MCAO; but not after 90 minutes of occlusion. With 60 minutes of transient ischemia, the diffusion/perfusion mismatch was similar, but after reperfusion, the lesion volumes on ADC and cerebral blood flow maps became much smaller. There was a significant difference in 24- hour infarct volumes between the permanent and temporary occlusion groups.     

Local mild hypothermia with thrombolysis for acute ischemic stroke within a 6-h window

Objective

To determine the safety and efficacy of combined local mild hypothermia and IV rtPA in treating acute ischemic stroke (AIS) patients with MRI perfusion- and diffusion-weighted imaging (PWI/DWI) mismatch within a 6-h stroke window.

Methods

AIS patients within 6 h of a minimum 20% PWI/DWI MRI mismatch were randomly assigned to 3 groups: local mild hypothermia with IV rtPA (Group A); IV rtPA (Group B); or conventional anti-platelet aggregation (Group C). Mortality and National Institutes of Health Stroke Scale (NIHSS) and the modified Rankin Scale (mRS) score and Barthel Index (BI) were used in evaluation.

Results

There were significant differences in NIHSS 24 h after treatment among the three groups (P < 0.001). Based on mRS and BI, more patients in Groups A and B showed favorable outcomes than patients in Group C (P = 0.017 and P = 0.009, respectively); however, there were no significant efficacy differences between Groups A and B. The incidence of symptomatic ICH and the mortality rates within 90 days in the 3 groups were similar. In addition, there were no significant differences in NIHSS improvement at 24 h and favorable outcomes 90 days after IV rtPA treatment between patients within 3 h and 3–6 h from symptom onset.

Conclusions

There was no benefit of combined local hypothermia/IV rtPA treatment compared to IV rtPA alone. PWI/DWI mismatching on MRI can be a selection criteria for IV rtPA treatment within a 6-h window.