Ischemic lesion growth in acute stroke: Water uptake quantification distinguishes between edema and tissue infarct

Abstract

Infarct growth from the early ischemic core to the total infarct lesion volume (LV) is often used as an outcome variable of treatment effects, but can be overestimated due to vasogenic edema. The purpose of this study was (1) to assess two components of early lesion growth by distinguishing between water uptake and true net infarct growth and (2) to investigate potential treatment effects on edema-corrected net lesion growth. Sixty-two M1-MCA-stroke patients with acute multimodal and follow-up CT (FCT) were included. Ischemic lesion growth was calculated by subtracting the initial CTP-derived ischemic core volume from the LV in the FCT. To determine edema-corrected net lesion growth, net water uptake of the ischemic lesion on FCT was quantified and subtracted from the volume of uncorrected lesion growth. The mean lesion growth without edema correction was 20.4 mL (95% CI: 8.2–32.5 mL). The mean net lesion growth after edema correction was 7.3 mL (95% CI: −2.1–16.7 mL; p < 0.0001). Lesion growth was significantly overestimated due to ischemic edema when determined in early-FCT imaging. In 18 patients, LV was lower than the initial ischemic core volume by CTP. These apparently “reversible” core lesions were more likely in patients with shorter times from symptom onset to imaging and higher recanalization rates.

Perfusion imaging-based tissue-level collaterals predict ischemic lesion net water uptake in patients with acute ischemic stroke and large vessel occlusion

“…15 Consequently, there is an urgent need for reliable imaging biomarkers that strongly correlate with time-dependent ischemic edema formation and functional outcome after treatment. 3 Our finding that increased ischemic lesion NWU strongly predicts functional outcome are line with prior studies. 2,3,9,10,15 Interestingly, we found that favorable TLC and lower ischemic lesion NWU were strong predictors of good functional outcome regardless of CTA collateral status.…”

“…3 Our finding that increased ischemic lesion NWU strongly predicts functional outcome are line with prior studies. 2,3,9,10,15 Interestingly, we found that favorable TLC and lower ischemic lesion NWU were strong predictors of good functional outcome regardless of CTA collateral status. The uncoupling of CTA collateral robustness, despite being an independent predictor of final infarct volume, from TLC as a predictor of functional outcome in AIS-LVO patients has been described before.…”

“…2 Extensive tissue-edema formation indicates more profound ischemic damage to the brain and is associated with larger ischemic core lesions and increased risk of secondary intracranial hemorrhage in patients with AIS-LVO. 2,3 An adequate assessment of brain edema is crucial for monitoring patients' clinical course and the identification of imaging biomarkers associated with brain edema progression are an elementary challenge of acute stroke imaging. 4 Robust pial arterial collaterals may temporarily preserve blood flow to otherwise critically hypoperfused brain tissue.…”

“…5,6 Collateral status is commonly assessed on baseline CT-angiography (CTA) images and has been associated with lower baseline infarct core volumes, smaller early edema formation and infarct progression in AIS-LVO patients. 3,[7][8][9][10] However, collateral assessment on CTA is not standardized, subject to variable interpretation depending upon the used imaging technique, and may be unreliable to accurately measure cerebral perfusion. 5 Tissue-level collaterals (TLC) are assessed automatically and standardized on CT or MRI perfusion imaging by the hypoperfusion intensity ratio (HIR) and have been associated with infarct progression, final core volume and favorable outcomes regardless of CTA collateral status.…”

The Role of Edema in Subacute Lesion Progression After Treatment of Acute Ischemic Stroke

“…Broocks et al have developed a densitometry based NWU measure that relies on the relationship of increasing lesion volume due to water content and the associated density reduction on NCCT (18). Due to the increased reliability to distinguish EV from within the ischemic lesion compared to the global imaging markers and its easy applicability to widely available NCCT scans, this method was utilized in this study (7,(19)(20)(21).…”