Prevalence and significance of hyperdense middle cerebral artery in acute stroke.

BACKGROUND AND PURPOSE Early noncontrast computed tomographic scans may visualize a hyperdense middle cerebral artery before the infarct becomes visible. This sign disappears within a few days, corresponds to the clot itself, and might be associated with a poor prognosis. The aim of the study was to determine its prevalence, diagnostic value, relationship to demographic data, ability to separate embolic from nonembolic causes, short-term prognostic value, evolution over time, and relationship to arterial occlusion on angiography. METHODS We performed this study using computed tomographic scans performed within 12 hours after onset in 272 consecutive unselected patients with a first acute cerebrovascular event. RESULTS Seventy-three subjects had the hyperdense middle cerebral artery sign, leading to a prevalence of 26.8% in the whole group and 41.2% in patients with a middle cerebral artery infarct. Specificity was 100%, but sensitivity was only 30%. This sign was not dependent on cerebrovascular risk factors, but was more likely to occur in cortical and in large, deep, middle cerebral artery infarcts (p less than 0.01). It provided only a 3.5% gain in predicting death, and one fifth of patients with the sign recovered within 2 weeks; this sign was not an independent variable of poor outcome on multiple linear regression. It spontaneously disappeared within a few days and was always related to an occlusion of the middle cerebral artery in patients who underwent early angiography. CONCLUSIONS The hyperdense middle cerebral artery sign is useful in the diagnosis of middle cerebral artery occlusion but does not always predict a poor prognosis.