Abstract TP539: The Complement Protein C1q is Elevated Early in Cerebrospinal Fluid After Subarachnoid Hemorrhage but Decreased in Patients With Symptomatic Vasospasm

Abstract

Introduction: Neuroinflammation is common after subarachnoid hemorrhage (SAH). The complement protein C1q is a well-known inflammatory mediator that has emerged as a key player in neuroimmune synaptic alterations. In this study, we sought to evaluate changes in cerebrospinal fluid (CSF) C1q after SAH and its association with outcome and symptomatic vasospasm (sVS). Methods: Subjects with SAH were recruited from a regional referral center. Cases were eligible to participate if they had nontraumatic aneurysmal SAH and an external ventricular drain. Samples were obtained within 72 hours of symptom onset. Control subjects were those undergoing lumbar puncture with normal CSF and normal brain MRI. C1q levels were determined using commercially available ELISA, normalized by total CSF protein, and divided into tertiles. SAH subjects were prospectively followed through hospitalization and categorized into those with good outcome (Glasgow Outcome Scale, GOS, of 5) or poor outcome (GOS of 2-4). Patients were also further categorized into those with and without sVS, defined by the presence of arterial narrowing on angiography and neurological deterioration. The rates of patients with poor outcome and sVS in each C1q tertile were compared. Results: We analyzed the CSF of 29 SAH and 11 control patients. Mean age of SAH patients was higher than controls (53.2 vs. 42.0, p=0.03) while there were no sex differences across groups. Levels of C1q were elevated in SAH patients compared to controls (p=0.02). Within the SAH group, 7 (24%) were defined as good outcome while 22 (76%) were defined as poor outcome. Mean C1q levels were comparable between these two groups (p=0.61). Symptomatic vasospasm occurred in 18 (62%) SAH patients - 16 (89%) with poor outcome and 2 (11%) with good outcome. Patients with sVS had decreased levels of C1q compared to those without (p=0.03). The rate of poor outcome per tertile of C1q was 100%, 60%, and 70%, while the rate of sVS per tertile was 88%, 70%, and 40% of patients. Conclusions: The complement protein C1q is elevated in CSF of SAH patients and may contribute to early neuroinflammation. C1q levels also appear to be lower in patients who experience sVS, suggesting that elevated C1q may have a protective role in early SAH.