Wall Enhancement of Coiled Intracranial Aneurysms Is Associated with Aneurysm Recanalization: A Cross-Sectional Study

Patient Recruitment

We conducted this retrospective study according to the guidelines of the Declaration of Helsinki with approval of the local ethics committee of the Medical University of Graz (34–029 ex 21/22). We obtained written informed consent from all patients. During 16 months, we consecutively collected data from patients assigned to our department for routine follow-up of treated intracranial aneurysms. We excluded patients treated with alternative or additional treatment methods to coiling such as microsurgical clipping or flow diverters and those with insufficient image quality or known allergy to MR imaging contrast agents.

Imaging

We performed all imaging on a 3T Magnetom Prisma whole-body MR imaging system (Siemens). Patients underwent a standard protocol for aneurysm follow-up with fixed time points for contrast administration and postcontrast imaging (0.2 mmol/kg body weight of Dotarem; Guerbet). To assess any enhancement of aneurysms, we used a 2D T1WI black-blood TSE sequence (flip angle = 180°, TE/TR = 12/800 ms, FOV = 170 mm, voxel size = 0.5 × 0.5 × 2.5 mm) pre- and postcontrast. For assessment of aneurysm recanalization size, we used TOF angiography postcontrast.

Image Analysis

Two experienced neuroradiologists blinded to patient history or aneurysm status performed image analyses (S.L.L. and E.M.H.). A third experienced neuroradiologist resolved disagreements between the 2 raters (H.D.).

We defined recanalization as a recurrence of an initially completely coiled, occluded aneurysm (Raymond Roy I). We defined AWE as enhancement of the aneurysm wall compared with noncontrast T1WI and ACE as enhancement of the intraluminal parts of the aneurysm compared with noncontrast T1WI. AWE and ACE represent binary metrics (present or not present). We considered any signal increase on noncontrast T1WI compared with surroundings without further signal increase after contrast administration as rim artifacts.

The presence of SAH was confirmed on a CT scan followed by a CTA to confirm the presence of an intracranial aneurysm. Findings of unruptured intracranial aneurysms were incidental on CTA or MRA. The initial diameters of an aneurysm were determined on diagnostic DSA before coiling. To assess an increase of total aneurysm size after embolization, we compared the initial maximum aneurysm diameter before coiling with the current maximum aneurysm diameter on follow-up MR imaging to evaluate a potential difference in total aneurysm size. For recanalization size, we used the largest recanalization diameter on follow-up MRA.

For comparison of the incidence of AWE or ACE after coil embolization with regard to follow-up time after treatment, we categorized coiled aneurysms into our standard follow-up intervals: up to 6 months, 7–12 months, 13–24 months, 25–48 months, 49–72 months, 73–96 months, and >96 months. For comparison of the incidence of AWE or ACE after coil embolization regarding aneurysm recanalization size, we compared those with aneurysms without recanalization with groups with aneurysm recanalization of 1–3 mm, 4–5 mm, and ≥6 mm.

Statistical Analysis

We performed all statistical analyses in SPSS Statistics, Version 27.0.1.0 (IBM) and presented continuous variables as mean (SD) and categoric variables as absolute numbers (percentage). For comparison of categoric variables, we used the Fisher exact test or χ² test if applicable. We tested continuous variables for normal distribution using the Shapiro-Wilk test and used the Mann-Whitney U test for non-normally distributed variables or the Student t test for normally distributed variables to assess group differences at a significance level of .05.

To assess interrater agreement for aneurysm enhancement patterns, we used the Cohen κ with κ values of 0 for no agreement, 0.10–0.20 for slight agreement, 0.21–0.40 for fair agreement, 0.41–0.60 for moderate agreement, 0.61–0.80 for substantial agreement, 0.81–0.99 for near-perfect agreement, and 1 for perfect agreement.

To analyze the potential effects on the recanalization size, we considered AWE, ACE, aneurysmal SAH, age, biologic sex, occurrence of aneurysm regarding the anterior or posterior circulation, and the difference in maximum aneurysm size before and after coil embolization as independent variables for a linear multivariate regression analysis. We excluded direct measurements of aneurysm size because of codependency. We were not able to determine the preinterventional maximum diameter of 3 aneurysms due to lack of data. In 1 case, we could not determine the ACE due to pulsation artifacts. We excluded these cases from the respective analyses. The authors S.L.L. and G.R. functioned as statistical guarantors.