Novel in vivo Assessment of Unruptured Intracranial Aneurysm Inflammatory Factors

Intraluminal assessment of inflammatory factors in patients with intracranial aneurysms

BACKGROUND

The formation, growth, and rupture of intracranial aneurysms (IA) are due to several pathophysiological mechanisms, including focal hemodynamic injury and inflammation of the arterial wall. We investigated the differences between venous, parent artery, and intra-aneurysmal blood by measuring inflammatory factors and antibodies in patients with ruptured (rIA) or unruptured intracranial aneurysms (uIA).

METHOD

A prospective study was performed in patients who presented with IA and required endovascular treatment. Blood was drawn from the lumen of the aneurysm sac, the parent artery, and the peripheral veins, to determine the serum concentrations of complement factors C3, C4, IgG, IgM, IgA antibodies, and C-reactive protein (CRP).

RESULTS

Thirty-six patients (15 with uIA and 21 with rIA) were enrolled in the study. In both groups, C3, C4, IgM, IgG, and IgA showed a gradual decrease from venous to intra-aneurysmal samples, but only IgG in the parent artery and intra-aneurysmal samples reached a significant decrease in uIA compared with venous samples. Accordingly, C3 and IgG concentrations in the intra-aneurysmal samples showed a significant decrease in rIA compared with venous samples. A significant increase in CRP concentrations was observed in parent artery and intra-aneurysmal samples from patients with rIA compared with patients with uIA; a significant increase in C3 concentrations was observed in parent artery samples from patients with rIA compared with patients with uIA, and a significant decrease in IgM concentrations was observed in venous, parent artery, and intra-aneurysmal samples from patients with rIA compared with patients with uIA.

CONCLUSIONS

A decrease in C3 and IgG in the aneurysm sac indicates activation of the complement system in the arterial wall. CRP in the aneurysm sac and lumen of the parent artery was significantly increased in ruptured compared with unruptured aneurysms, whereas venous, parent artery, and intra-aneurysmal IgM were decreased in ruptured compared with unruptured aneurysms. These results argue for the role of an ongoing inflammatory process in aneurysms leading to their growth and rupture.

Growth and rupture of an intracranial aneurysm: the role of wall aneurysmal enhancement and CD68

Introduction

Intracranial aneurysms occur in 3%-5% of the general population. While the precise biological mechanisms underlying the formation, growth, and sudden rupture of intracranial aneurysms remain partially unknown, recent research has shed light on the potential role of inflammation in aneurysm development and rupture. In addition, there are ongoing investigations exploring the feasibility of employing new drug therapies for controlling the risk factors associated with aneurysms. CD68, a glycosylated glycoprotein and the human homolog of macrosialin, is prominently expressed in monocyte/macrophages within inflamed tissues and has shown potential application in oncology. An observational study was conducted with the aim of comparing the histological characteristics of aneurysm walls with preoperative MRI scans, specifically focusing on CD68 activity.

Method

An observational pilot study was conducted to investigate the histological characteristics of the aneurysm wall that could be potentially associated with aneurysm growth and rupture. A total of 22 patients diagnosed with ruptured and unruptured intracranial aneurysms who had undergone conventional clipping between January 2017 and December 2022 were included in the study.

Results

A histopathological analysis of the aneurysm wall was performed in all patients, particularly focusing on the presence of CD68. A preoperative MRI with gadolinium was conducted in 10 patients with unruptured aneurysms and six patients with ruptured aneurysms. An emergency clipping was performed in the remaining six patients. The results showed that CD68 positivity and wall enhancement were significantly associated with intracranial aneurysm wall degeneration, growth, and rupture.

Conclusion

The histological and radiological inflammatory findings observed in the wall of cerebral aneurysms, as well as the CD68 positivity, are significantly associated with the risk of intracranial aneurysm growth and rupture. This study highlights the crucial importance of considering clinical and medical data when making treatment decisions for intracranial aneurysms. Furthermore, it emphasizes the relevance of evaluating wall enhancement in MRI scans as part of the diagnostic and prognostic process.

The Role of Soluble Urokinase Plasminogen Activator Receptor (suPAR) in the Context of Aneurysmal Subarachnoid Hemorrhage (aSAH)—A Prospective Observational Study

Objective

Outcome after aneurysmal subarachnoid hemorrhage (aSAH) is highly variable and largely determined by early brain injury and delayed cerebral ischemia (DCI). Soluble urokinase plasminogen activator receptor (suPAR) represents a promising inflammatory marker which has previously been associated with outcome in traumatic brain injury and stroke patients. However, its relevance in the context of inflammatory changes after aSAH is unclear. Here, we aimed to characterize the role of circulating suPAR in both serum and cerebrospinal fluid (CSF) as a novel biomarker for aSAH patients.

Methods

A total of 36 aSAH patients, 10 control patients with unruptured abdominal aneurysm and 32 healthy volunteers were included for analysis. suPAR was analyzed on the day of admission in all patients. In aSAH patients, suPAR was also determined on the day of DCI and the respective time frame in asymptomatic patients. One- and two-sample t-tests were used for simple difference comparisons within and between groups. Regression analysis was used to assess the influence of suPAR levels on outcome in terms of modified Rankin score.

Results

Significantly elevated suPAR serum levels (suPAR-SL) on admission were found for aSAH patients compared to healthy controls, but not compared to vascular control patients. Disease severity as documented according to Hunt and Hess grade and modified Fisher grade was associated with higher suPAR CSF levels (suPAR-CSFL). In aSAH patients, suPAR-SL increased daily by 4%, while suPAR-CSFL showed a significantly faster daily increase by an average of 22.5% per day. Each increase of the suPAR-SL by 1 ng/ml more than tripled the odds of developing DCI (OR = 3.06). While admission suPAR-CSFL was not predictive of DCI, we observed a significant correlation with modified Rankin's degree of disability at discharge.

Conclusion

Elevated suPAR serum level on admission as a biomarker for early inflammation after aSAH is associated with an increased risk of DCI. Elevated suPAR-CSFL levels correlate with a higher degree of disability at discharge. These distinct relations and the observation of a continuous increase over time affirm the role of inflammation in aSAH and require further study.