Thin-section diffusion-weighted imaging of the infratentorium in patients with acute cerebral ischemia without apparent lesion on conventional diffusion-weighted imaging.
ABSTRACT False-negative diffusion-weighted (DW) imaging findings are often encountered during the acute stage of cerebral ischemia. The types of acute ischemia most likely to be missed by conventional DW imaging, and the utility of additional thin-section DW imaging of the infratentorium were investigated in 192 consecutive patients admitted within 24 hours of the onset of ischemic symptoms. If 6-mm section DW imaging at admission showed no obvious lesion, additional 3-mm section DW imaging of the infratentorium was performed. Six-mm section DW imaging failed to demonstrate ischemic lesion in 32 patients; 18 patients with transient ischemic attack (TIA), 13 with infratentorial infarction, and one with supratentorial infarction. Three-mm section DW imaging revealed the ischemic lesions in 12 of these 32 patients. Most patients with negative 6-mm section DW imaging findings at admission suffered from either infratentorial infarction or TIA. If 6-mm section DW imaging shows no ischemic lesion, 3-mm section DW imaging of the infratentorium is considered to be useful for detection of the lesion.
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ABSTRACT: Recently, a new definition of transient ischemic attack (TIA) has been proposed based on the duration of symptoms and diffusion-weighted imaging (DWI) findings. We investigate the value of temporal and neuroimaging data on the prognoses of TIA patients. Clinical data, symptom duration, DWI, and ultrasonographic findings were collected in 83 consecutive classical TIA patients attended in the emergency department. Stroke recurrence, myocardial infarction, or any vascular event was recorded at follow-up (mean of 389 days). A total of 27 (32.5%) patients revealed focal abnormalities on DWI, whereas 37(44.6%) had symptoms lasting >1 hour. Large-artery disease was detected in 37 (44.6%) patients. Twenty (24.1%) patients experienced an endpoint: 2 (2.4%) myocardial infarctions, 16 (19.3%) cerebral ischemic events, and 2 cases (2.4%) of peripheral arterial disease. Cox proportional hazards multivariate analyses identified the association of symptoms >1 hour with DWI abnormalities as independent predictors of further cerebral ischemic events or any vascular event (hazard ratio [HR], 5.02; CI, 1.37 to 18.30; P=0.015; and HR, 3.77; CI, 1.09 to 13.00; P=0.029). Large-artery occlusive disease also remained an independent predictor of both endpoints (HR, 4.22; CI, 1.17 to 15.22; P=0.028; and HR, 3.60; CI, 1.14 to 11.39; P=0.0293). TIA patients with DWI abnormalities associated with duration of symptoms >1 hour and those with large-artery occlusive disease have a higher risk of further vascular events. Routine use of DWI and Doppler ultrasonographic examinations will be useful for identifying TIA patients at high risk to plan aggressive prevention therapies.Stroke 10/2004; 35(10):2313-9. · 6.16 Impact Factor
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ABSTRACT: Lesions associated with acute stroke are often missed by diffusion-weighted imaging (DWI), suggesting that the sensitivity of this technique for detecting acute ischemic stroke may not be as high as initially thought. Our aim was to estimate the rate of false-negative DWI studies in patients with persistent neurologic deficit due to an ischemic stroke and to identify which stroke lesions are most likely to be missed by DWI. We reviewed MR images obtained within 48 hours after stroke onset in 139 patients admitted for symptoms consistent with ischemic stroke in whom the deficit lasted more than 24 hours. Cases of negative initial DWI findings with an ischemic lesion visible on follow-up MR studies and a final diagnosis of arterial ischemic stroke were analyzed in terms of delay between onset of symptoms and initial DWI (MR latency), size and vascular distribution of the lesions, and relationship to findings in patients with positive initial DWI results. We found eight cases (5.8%) of false-negative initial DWI studies, of which four were positive on initial fluid-attenuated inversion recovery (FLAIR) imaging. Follow-up FLAIR/DWI showed a hyperintensity matching clinical presentation in all eight patients. The mean size of the lesion was 0.19 +/- 0.16 cm3. False-negative studies occurred more often in cases of stroke in the posterior (19%) than in the anterior (2%) circulation or when DWI was obtained within 24 hours after symptom onset. Of the six false-negative vertebrobasilar stroke lesions, five were located in the brain stem. In all, 31% of patients with vertebrobasilar ischemic stroke had a false-negative initial DWI study during the first 24 hours. A false-negative DWI study is not uncommon during the first 24 hours of ischemic stroke. Vertebrobasilar stroke should therefore not be ruled out on the basis of early negative DWI, especially when symptoms persist and are suggestive of this diagnosis.American Journal of Neuroradiology 10/2000; 21(8):1434-40. · 3.17 Impact Factor
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ABSTRACT: We sought to characterize the evolution of acute ischemic stroke by MRI and its relationship to patients' neurological outcome. Fourteen patients with acute ischemic stroke underwent MRI within 13 hours of symptom onset (mean, 7.4+/-3 hours) and underwent repeated imaging and concurrent neurological examination at 8, 24, 36, and 48 hours and 7 days and >42 days after first imaging. Diffusion-weighted imaging (DWI) lesion volumes increased between the first and second scans in 10 of 14 patients; scans with maximum DWI lesion volume occurred at a mean of 70.4 hours. Initial DWI lesion volume correlated with the largest T2 lesion volume (r=0.97; P<0.001). Final lesion volume was smaller than maximum lesion volume in 12 of 14 patients. There was positive correlation between the follow-up National Institutes of Health Stroke Scale score and the initial DWI lesion volume (r=0.67; P=0. 01) and maximum T2 lesion volume (r=0.77; P<0.01) and negative correlation with initial mean apparent diffusion coefficient ratio (ADCr) (r=-0.64; P<0.05). The ADCr was 0.73 at initial imaging and fell between the initial and second scans in 10 of 14 patients. Mean ADCr did not rise above normal until 42 days after stroke onset (P<0. 001). Serial MRI demonstrates the dynamic nature of progressive ischemic injury in acute stroke patients developing over hours to days, and it suggests that both primary and secondary pathophysiological processes can be valuable targets for neuroprotective interventions.Stroke 11/1998; 29(11):2268-76. · 6.16 Impact Factor