Classification and hemodynamic characteristics of delayed intracerebral hemorrhage following stent-assisted coil embolism in unruptured intracranial aneurysms

Abstract

Background and objective: Stent-assisted coil (SAC) embolization is a commonly used endovascular treatment for unruptured intracranial aneurysms (UIAs) but can be associated with symptomatic delayed intracerebral hemorrhage (DICH). Our study aimed to investigate the hemodynamic risk factors contributing to DICH following SAC embolization and to establish a classification for DICH predicated on hemodynamic profiles.

Methods: This retrospective study included patients with UIAs located in the internal carotid artery (ICA) treated with SAC embolization at our institution from January 2021 to January 2022. We focused on eight patients who developed postoperative DICH and matched them with sixteen control patients without DICH. Using computational fluid dynamics, we evaluated the hemodynamic changes in distal arteries [terminal ICA, the anterior cerebral artery (ACA), and middle cerebral artery (MCA)] pre-and post-embolization. We distinguished DICH-related arteries from unrelated ones (ACA or MCA) and compared their hemodynamic alterations. An imbalance index, quantifying the differential in flow velocity changes between ACA and MCA post-embolization, was employed to gauge the flow distribution in distal arteries was used to assess distal arterial flow distribution.

Results: We identified two types of DICH based on postoperative flow alterations. In type 1, there was a significant lower in the mean velocity increase rate of the DICH-related artery compared to the unrelated artery (-47.25 ± 3.88% vs. 42.85 ± 3.03%; p < 0.001), whereas, in type 2, there was a notable higher (110.58 ± 9.42% vs. 17.60 ± 4.69%; p < 0.001). Both DICH types demonstrated a higher imbalance index than the control group, suggesting an association between altered distal arterial blood flow distribution and DICH occurrence.

Conclusion: DICH in SAC-treated UIAs can manifest as either a lower (type 1) or higher (type 2) in the rate of velocity in DICH-related arteries. An imbalance in distal arterial blood flow distribution appears to be a significant factor in DICH development.

Keywords: delayed intracerebral hemorrhage; endovascular treatment; hemodynamics; intracranial aneurysms; stent-assisted coil embolization.

Figure 1

View of the measurement plane in the patient’s aneurysm and vascular model: the measurement planes were the test section of ICA (blue), the ACA (brown), and the MCA (green).

Figure 2

Comparison of the increase rate of velocity between DICH related and unrelated artery in both type 1 and type 2 DICH patients.

Figure 3

Comparison of the imbalance index of distal arteries in flow velocity between DICH group (both type 1 and type 2) and control group (A,B) and between type 1 and type 2 DICH patients (C).

Figure 4

A posterior communicating segment aneurysm of left ICA in DICH of type 1 was treated with EP2 stent assisted coiling. (A) Preprocedural angiography of the aneurysm and (B) postprocedural immediate angiography revealed Raymond grade 2. (C) The coiled aneurysm was showed by CT scan at 24 h later after the treatment. (D) CT scan obtained 4 days post-procedure, revealing ipsilateral frontal lobe DICH with surrounding infarcted area (asterisk). A significant increase in velocity was observed on the terminal section of the ICA (F) compared to the preoperative results (E) by computer hemodynamic detection (Increase rate was 44.9%). The velocity of DICH related artery (ACA) decreased significantly after embolization with increase rate of-35.9% (G,H), while the flow velocity of DICH unrelated artery (MCA) increased with increase rate of 35.7% (I,J). The imbalance index of this patient was 71.6%.

Figure 5

An ophthalmic segment aneurysm of the left ICA in DICH of type 2 was treated with EP2 stent assisted coiling. (A) Preprocedural angiography of the aneurysm and (B) postprocedural immediate angiography revealed Raymond grade 1. (C) The coiled aneurysm was showed by CT scan at 24 h later after the treatment. (D) CT scan obtained 3 days post-procedure, revealing ipsilateral temporal lobe DICH (arrow). A significant increase in velocity was observed on the terminal section of the ICA (F) compared to the preoperative results (E) by computer hemodynamic detection (Increase rate was 47.4%). The velocity of DICH related artery (MCA) increased significantly after embolization with an increase rate of 77.0% (I,J), while the flow velocity of DICH unrelated artery (ACA) increased with increase rate of 20.7% (G,H). The imbalance index of this patient was 56.3%.

Figure 6

(A,B) An ophthalmic segment aneurysm in a left ICA without DICH in the control group was treated with EP2 stent assisted coiling, and a postprocedural immediate angiography revealed Raymond grade 1. A significant increase in velocity was observed on the terminal section of the ICA (D) compared to the preoperative results (C) by computer hemodynamic detection (Increase rate was 47.2%). The flow velocity of ACA (E,F) and MCA (G,H) increased significantly after embolization with increase rate of 22.5% and 41.3%, respectively. The imbalance index of this patient was 18.8%.