Carly S Rivers | PubMed Health

PubMed2006

Persistent infarct hyperintensity on diffusion-weighted imaging late after stroke indicates heterogeneous, delayed, infarct evolution.

BACKGROUND AND PURPOSE: Some infarcts have persistently hyperintense areas on diffusion-weighted MRI (DWI) even at 1 month after stroke, whereas others have become isointense to normal brain. We hypothesized that late DWI hyperintensity reflected different infarct evolution compared with areas that were isointense by 1 month. METHODS: We recruited patients prospectively with ischemic stroke, performed DWI and perfusion-weighted MRI (PWI) on admission, at 5 days, 14 days, and 1 month after stroke, and assessed functional outcome at 3 months (Rankin Scale). Patient characteristics and DWI/PWI values were compared for patients with or without "still hyperintense" infarct areas on 1-month DWI. RESULTS: Among 42 patients, 27 (64%) had "still hyperintense" infarct regions at 1 month, mostly in white matter. Patients with "still hyperintense" regions at 1 month had lower baseline apparent diffusion coefficient ratio (ADCr; mean+/-SD 0.76+/-0.12 versus 0.85+/-0.12; hyperintense versus isointense; P<0.05), prolonged reduction of ADCr (repeated-measures ANOVA; P<0.01), no difference in baseline perfusion but delayed normalization of mean transit time (P<0.05) and cerebral blood flow ratios (repeated measures ANOVA; P<0.05), initially more severe stroke, and worse 3-month outcome than patients whose lesions were isointense by 1 month. CONCLUSIONS: The late DWI lesion hyperintensity emphasizes the heterogeneity in temporal evolution of stroke injury and suggests ongoing "ischemia." Lower baseline ADCr precedes delayed perfusion normalization, suggesting that worse cell swelling impedes reperfusion. Further study is required to determine underlying mechanisms and any potential for subacute intervention to improve recovery.

Adult↗

PubMed2005

What has diffusion imaging in animals told us about diffusion imaging in patients with ischaemic stroke?

BACKGROUND AND PURPOSE: In acute ischaemic stroke, the amount (and type) of cellular damage underlying diffusion-weighted imaging (DWI) lesion appearances is unclear. We summarized all information from experimental studies of DWI in focal ischaemia models. METHODS: We systematically reviewed all published studies of DWI in focal ischaemic stroke models. We extracted key experimental details to determine CORRELATIONS between histological features and DWI lesion characteristics. RESULTS: Of 141 potentially eligible papers (including more than 2,817 animals, mostly rats), details of key experimental methods were unfortunately often omitted. Consistent findings amongst high-quality studies with blinded analysis included: neuronal damage persists or progresses despite early DWI lesion 'normalisation'; the apparent diffusion coefficient is not very sensitive to the amount of neuronal damage; the 'brighter' the DWI lesion, the greater the neuronal damage; and the DWI lesion may reflect glial more than neuronal changes. Anaesthesia and fixation techniques may inadvertently affect these findings. CONCLUSIONS: The relationship between cellular damage and DWI lesion appearance, particularly recovery patterns in reperfusion experiments, remains imprecise. Key experimental details could be reported more completely and consistently. Potential problems from repeated anaesthetics need to be addressed. Early DWI lesion 'recovery' in acute stroke patients may largely reflect glial rather than neuronal 'recovery'.

Animals↗