A CRITICAL REEVALUATION OF THE INTRALUMINAL THREAD MODEL OF FOCAL CEREBRAL-ISCHEMIA - EVIDENCE OF INADVERTENT PREMATURE REPERFUSION AND SUBARACHNOID HEMORRHAGE IN RATS BY LASER-DOPPLER FLOWMETRY

Background and Purpose-The intraluminal thread model for middle cerebr al artery occlusion (MCAO) has gained increasing acceptance. Numerous modifications have been reported in the literature, indicating that th e technique has not been standardized. The present study was performed to evaluate and optimize the reliability of this model. Methods-One h undred Sprague-Dawley rats were subjected to MCAO by 2 different intra luminal filaments. Cortical blood flow was continuously monitored over both hemispheres by laser-Doppler flowmetry (LDF). In part I (3-0 fil ament), we evaluated the incidence of adequate MCAO, subarachnoid hemo rrhage (SAH), intraluminal thrombus formation, and the effects of hepa rinization. In part II (silicone-coated 4-0 filament), we also determi ned the influence of insufficient MCAO on morphological and functional outcome and the incidence of postischemic hyperthermia. Results In pa rt I, SAH occurred in 30% and premature reperfusion in 24%. All animal s with a decrease in contralateral flow had suffered SAH. Thrombus for mation was not observed in any group. In part II, SAH occurred in 8% a nd premature reperfusion in 26%. Then was no difference in outcome bet ween rats with primary MCAO and rats with filament correction. Animals with uncorrected premature reperfusion had significantly smaller infa rct volumes and fewer neurological deficits. Conclusions CAH and insuf ficient MCAO may be more common in the intraluminal thread model than previously reported. Inadvertent premature reperfusion contributes to the interanimal variability associated with this model. The incidence of valid experiments increases with the use of a silicone-coated 4-0 f ilament. Continuous bilateral LDF is indispensable to monitor adequate MCAO and is highly sensitive to recognize SAH.