Early Ischemic Edema on Cerebral Computed Tomography: Its Relation to Diffusion Changes and Hypoperfusion within 6 h after Human Ischemic Stroke

Abstract

Background: Brain tissue hypoattenuation on early computed tomography is frequently included in decision making in acute stroke management. However, its pathophysiological counterpart needs further evaluation. Methods: By comparative imaging with diffusion-weighted imaging and ¹⁵O-water positron emission tomography we aimed to interpret early (<6 h) hypoattenuation. Results: In 11 patients, the hypoattenuation corresponded to a decreased proton diffusion (median 115.9% relative DWI value) measured by magnetic resonance imaging and to a severe hypoperfusion (below 12 ml/100 g/ min) assessed by positron emission tomography. The volume of parenchymal hypoattenuation correlated to the tissue with disturbed diffusion (Spearman’s rho = 0.73), but largely underestimated the hypoperfusion below 20 ml/100 g/min. Conclusions: Early hypoattenuation reflects the coupling of the severity of ischemia and resulting diffusion changes. It allows an estimate of the infarct core but underestimates the penumbral hypoperfusion.

CT Angiographic Source Images: Flow- or Volume-Weighted?

“…Hypoattenuation seen on NCCT correlates with severe hypoperfusion and decreased proton diffusion representing irreversible ischemic injury. 23,28 NCCT hypoattenuation is due to extra-to intracellular shift of brain tissue water, whereas hypoattenuation of CTA-SI most likely reflects reduction in blood and, therefore, contrast distribution to the affected territory. 9 Several earlier studies have suggested that CTA-SI are volume-weighted.…”

Alberta Stroke Program Early CT Scoring of CT Perfusion in Early Stroke Visualization and Assessment

“…[25][26][27] Early ischemic changes are difficult to detect on NCCT, with low interobserver agreement for presence and extent. 29,30 Whereas loss of gray-white differentiation is consistent with infarction, 31 cerebral swelling may be intermixed, extending the apparent boundary of infarct. Cerebral swelling is associated with a variable and lower stroke risk 32 and may account for overestimation of initial infarct size on NCCT.…”

Extremely Early Computed Tomography Signs in Hyperacute Ischemic Stroke as a Predictor of Parenchymal Hematoma

“…In a recent study using single-photon emission CT, the time from onset to CT and residual cerebral blood flow were independent factors that contributed to the presence of ECTs [16]. Another study using positron emission tomography also shows that ECTs reflect the coupling of the severity of ischemia [17]. These findings suggest that the earlier the manifestation of ECTs, the severer the depth of brain ischemia.…”