Intraoperative cerebral blood flow threshold standardization in a mouse model of global cerebral ischemia: Parallel evaluation of laser doppler flowmetry and laser speckle contrast imaging

Bilateral common carotid artery occlusion (BCCAO) is a widely used mouse model of global cerebral ischemia (GCI). However, marked inter-animal variability in ischemic severity, largely driven by anatomical heterogeneity of posterior communicating arteries (PcomAs), limits the reproducibility and comparability of this model. Although intraoperative real-time cerebral blood flow (CBF) monitoring offers a potential functional tool for predicting ischemic severity, validated threshold criteria for different monitoring platforms remain lacking. GCI was induced in male C57BL/6 J mice by 20 min of BCCAO. Cortical CBF was continuously monitored intraoperatively using either Laser Doppler Flowmetry (LDF) or Laser Speckle Contrast Imaging (LSCI). ROC analysis and K-means clustering were used to define optimal CBF reduction thresholds. Ischemic injury was evaluated by Nissl staining, H&E staining, and TUNEL staining in the hippocampal CA1 region at multiple time points after reperfusion. Functional outcomes were assessed using the Y-maze and contextual fear conditioning tests. PcomA score was significantly associated with the magnitude of intraoperative CBF reduction. ROC analysis identified an LDF-measured CBF reduction of ≥85% as the optimal threshold for distinguishing mice with low-collateral phenotype, whereas the corresponding threshold for LSCI was ≥80%. Mice meeting these thresholds showed pronounced delayed neuronal loss and increased apoptosis in the hippocampal CA1 region, together with selective impairments in spatial working memory and contextual memory, while basal motor performance remained preserved. This study establishes platform-specific intraoperative CBF reduction thresholds for two commonly used monitoring modalities in the mouse BCCAO model (LDF ≥ 85%; LSCI ≥80%). • PcomA anatomy is a major source of variability in the mouse BCCAO model. • Intraoperative LDF and LSCI identify low-collateral mice using CBF reduction thresholds of 85% and 80%. • Low-collateral mice show delayed hippocampal CA1 injury and memory impairment.