Abstract
“Fogging” is the temporary loss of visibility of an infarct on CT which occurs in the subacute phase at about 2 weeks after stroke. It occurs in up to 40% of medium to large infarcts on CT. It is unclear whether or how often fogging occurs on T2-weighted MR, but if it does occur, it can cause underestimation of true infarct size. This study examined the possible frequency and time scale of “fogging” on T2-weighted MR. We conducted a blinded, independent review of prospectively collected MR scans from patients with symptoms of cortical ischaemic stroke, scanned sequentially up to 7 weeks after stroke. On each scan maximum infarct area was measured, and the infarct extent and swelling were coded on a validated scale. “Fogging” was suggested by reduced infarct extent between initial and subsequent scans. In 30 patients (with 74 scans) there was some apparent “fogging” in 50% of patients between 6 and 36 days (median 10 days) after stroke. Reduction in infarct extent on T2-weighted MR which may be attributed to “fogging” occurs in a significant proportion of patients with cortical infarcts. This may lead to an underestimation of true final infarct extent. This suggests that true infarct extent on T2-weighted MR can probably only be assessed on scans obtained beyond 7 weeks after stroke.
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Acknowledgements
The original MR study was funded by the UK Medical Research Council Clinical Research Initiative in Clinical Neurosciences Grant reference G9301975. We are grateful to Dr. S. Gretton for assistance in the study.
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O’Brien, P., Sellar, R.J. & Wardlaw, J.M. Fogging on T2-weighted MR after acute ischaemic stroke: how often might this occur and what are the implications?. Neuroradiology 46, 635–641 (2004). https://doi.org/10.1007/s00234-004-1230-2
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DOI: https://doi.org/10.1007/s00234-004-1230-2