Introduction: Early cortical infarcts (ECI) are common in subarachnoid hemorrhage (SAH) patients, but animal models of this phenomenon are lacking and mechanisms are unknown. After subarachnoid infusion of fresh blood in the swine brain, we previously observed ECI in association with organized sulcal clots in some animals. Here we refined our model for improved consistency and to explore mechanisms by injecting clotted blood into a sulcus.
Methods: Juvenile swine underwent frontal craniotomy and cruciate sulcus exposure. The sulcus was injected with normal saline (surgical control), fibrin sealant (mass effect control), or autologous blood clotted ex vivo, followed by six hours of survival and electrocorticographic monitoring. Animals were then sacrificed for TTC and H&E staining.
Results: Sulcal injection of 1cc clotted blood caused persistent sulcal clots and adjacent cortical infarction in 6/6 animals. Cortical spreading depolarizations (CSD), a known mechanism of infarction, were recorded in 5/6 animals (count range: 4-20). H&E staining demonstrated well-demarcated cerebral edema and ischemic neuronal injury. To determine the roles of surgical injury and mass effect, subsequent groups were randomized to injection of normal saline (n=4), fibrin sealant (n=4), or autologous blood clot (n=5). While fibrin sealant and clot volumes did not differ (p=0.598), infarct volumes were significantly greater for the clot group (M=113.4 mm3, SD=45.3) than the fibrin sealant (M=45.2 mm3, SD=34.5) and saline (M=16.7 mm3, SD=12.8) groups (ANOVA [F(2,10)=9.1823, p=0.005] with Tukey-HSD [p’s<0.05]). Saline and fibrin sealant infarct volumes did not differ (p=0.510). Spearmann’s rank-order analysis demonstrated a significant correlation between CSD count and infarct volume across groups (rS(9)=0.767, p=0.006).
Conclusions: Organized sulcal clots cause adjacent cortical infarction, which cannot be attributed to surgical manipulation or mass effect alone. Further studies are needed to elucidate factors that trigger CSDs and ischemia and to test potential therapies targeting CSDs in this gyrencephalic model of clinical ECI.
Patient Care: We describe the first gyrencephalic large animal model to reliably reproduce the clinical phenotype of organized sulcal subarachnoid hemorrhage; recurrent cortical spreading depolarizations; and early cortical infarction. Our experiments provide further evidence of the relationship between early cortical infarction and organized sulcal subarachnoid clot. Furthermore, we demonstrate a significant correlation between the number of cortical spreading depolarizations and early cortical infarction volumes. This large-animal model of sulcal subarachnoid hemorrhage offers a platform for further investigation of the relationship between sulcal subarachnoid clot, CSD, and ECI as well as pharmacologic targeting of CSDs which can then be translated to the bedside to reduce the burden of ECI after aneurysmal SAH.
Learning Objectives: By the conclusion of this session, participants should be able to:
(1) Describe cortical spreading depolarizations as they relate to aneurysmal subarachnoid hemorrhage.
(2) Discuss, in small groups, the gyrencephalic porcine model of early cortical infarction after SAH; in particular, the relationship between sulcal subarachnoid clot, CSDs, and ECI.
(3) Identify potential further animal studies to investigate the relationship between SAH, CSD, and cortical infarction; identify CSD as a potential therapeutic target to reduce ECI after SAH.
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