Baseline magnetic resonance imaging parameters and stroke outcome in patients treated by intravenous tissue plasminogen activator.

BACKGROUND AND PURPOSE: We designed a prospective sequential pretreatment and posttreatment MRI study to assess the relation between neuroimaging parameters and clinical outcome in patients treated with intravenous recombinant tissue-type plasminogen activator (rtPA). METHODS: Patients with symptoms of acute hemispheric ischemic stroke were recruited. The National Institutes of Health Stroke Scale (NIHSS) score was assessed at baseline and at days 1, 7, and 60, and the modified Rankin scale (mRS) at day 60, by which outcome was classified in terms of independence (mRS score 0, 1, or 2) or severe disability or death (mRS score 3 through 6), was assigned. Multimodal stroke MRI was performed at presentation and repeated at day 1. MRI procedures included magnetic resonance angiography, T2* gradient-echo sequence, echoplanar imaging, and isotropic diffusion- (DWI) and perfusion-weighted (PWI) imaging. Patients were treated with intravenous rtPA after MRI completion. RESULTS: Twenty-nine patients (16 men and 13 women; mean+/-SD age, 65+/-14 years) underwent MRI; the mean time from symptom onset to treatment was 255+/-62 minutes. Twenty-six patients had a vessel occlusion, and 15 patients experienced a partial (Thrombolysis in Myocardial Infarction [TIMI]-2) or total (TIMI-3) recanalization at day 1, whereas 11 patients had a persistent occlusion. Mean NIHSS scores at day 60 were 5.7+/-5.4 if recanalization had occurred and 14+/-2 in cases of persistent occlusion. According to the mRS, 13 patients were independent (mRS 0 through 2), whereas severe disability or death (mRS 3 through 6) was observed in 15 patients. A better outcome was observed when recanalization was achieved (r=-0.68, P=0.0002). PWI volume and time to peak (TTP) within the DWI lesion assessed before therapy were correlated with day-60 NIHSS score (PWI volume: r=0.51, P=0.006, TTP: r=0.35, P=0.07). The day-0 DWI abnormality volume was well correlated with day-60 NIHSS score (r=0.58, P=0.001). Multiple regression linear analysis showed that 2 factors mainly influenced clinical outcome: (1) recanalization, with a high correlation with NIHSS score at day 60 (P=0.0001) and (2) day-0 DWI lesion volume, which is closely associated with day-60 NIHSS score (P=0.03). CONCLUSIONS: Baseline DWI volume and recanalization are the main factors influencing clinical outcome after rtPA for ischemic stroke.

Old microbleeds are a potential risk factor for cerebral bleeding after ischemic stroke: a gradient-echo T2*-weighted brain MRI study.

BACKGROUND AND PURPOSE: T2*-weighted gradient-echo MRI is known to detect old microbleeds (MBs), considered indicative of microangiopathy. MBs might be a potential risk factor for early cerebral bleeding (CB) after ischemic stroke. Therefore, we assessed the impact of MBs on the occurrence of CB after cerebral infarction. METHODS: We included prospectively stroke patients who had documented ischemic damage. The imaging protocol involved baseline CT scan, T2*-weighted gradient-echo MRI, diffusion-weighted imaging, T2-weighted imaging, and magnetic resonance angiography and had to be performed within 24 hours after symptom onset. The assessment of CB with T2*-weighted gradient-echo sequence necessitated a focal area of signal loss either within the ischemic area revealed by diffusion-weighted imaging or remote from it. Old MBs were defined on T2*-weighted images as homogeneous rounded areas of signal loss without surrounding edema. CT scan was systematically repeated within the first week to verify CB as diagnosed by the T2* weighted sequence. RESULTS: One hundred patients (mean age, 60 +/- 13 years; range, 19 to 83 years; 58 men, 42 women) met the inclusion criteria. MBs were seen in 20 patients on T2*-weighted imaging. Multivariate logistic regression analysis revealed that age, diabetes, previous use of antithrombotic drugs, evidence of an atherothrombotic source of stroke, and lacunar infarct were significantly associated with MBs (P<0.0001). CB was diagnosed in 26 patients: at the acute stage by T2*-gradient echo sequence in 18 patients and with CT scan performed within the first week in 8 patients. Multivariate logistic regression analysis showed that baseline National Institutes of Health Stroke Scale score, diabetes, and MBs were considered significant and independent predictors of CB (P<0.001). CONCLUSIONS: Although the pathogenesis of CB after ischemic stroke is multifactorial, the increased observation of CB in patients with MBs suggests that the associated vascular vulnerability contributes to CB.