Fogging on T2-weighted MR after acute ischaemic stroke: how often might this occur and what are the implications?
"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.
O'Brien
P
P
Department of Clinical Neurosciences, Western General Hospital, Crewe Rd., EH4 2XU, Edinburgh, UK.
Sellar
R J
RJ
Wardlaw
J M
JM
D020520:Brain Infarction / Q000473:pathology*; D002545:Brain Ischemia / Q000473:pathology*; D002560:Cerebrovascular Circulation; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013997:Time Factors