Noninvasive Angiographic Results of Clipped or Coiled Intracranial Aneurysms: An Inter- and Intraobserver Reliability Study

Abstract

Background and purpose: Noninvasive angiography is commonly used to assess the outcome of surgical or endovascular treatment of intracranial aneurysms in clinical series or randomized trials. We sought to assess whether a standardized 3-grade classification system could be reliably used to compare the CTA and MRA results of both treatments.

Materials and methods: An electronic portfolio composed of CTAs of 30 clipped and MRAs of 30 coiled aneurysms was independently evaluated by 24 raters of diverse experience and training backgrounds. Twenty raters performed a second evaluation 1 month later. Raters were asked which angiographic grade and management decision (retreatment; close or long-term follow-up) would be most appropriate for each case. Agreement was analyzed using the Krippendorff α (α_K) statistic, and the relationship between angiographic grade and clinical management choice, using the Fisher exact and Cramer V tests.

Results: Interrater agreement was substantial (α_K = 0.63; 95% CI, 0.55-0.70); results were slightly better for MRA results of coiling (α_K = 0.69; 95% CI, 0.56-0.76) than for CTA results of clipping (α_K = 0.58; 95% CI, 0.44-0.69). Intrarater agreement was substantial to almost perfect. Interrater agreement regarding clinical management was moderate for both clipped (α_K = 0.49; 95% CI, 0.32-0.61) and coiled subgroups (α_K = 0.47; 95% CI, 0.34-0.54). The choice of clinical management was strongly associated with the size of the residuum (mean Cramer V = 0.77 [SD, 0.14]), but complete occlusions (grade 1) were followed more closely after coiling than after clipping (P = .01).

Conclusions: A standardized 3-grade scale was found to be a reliable and clinically meaningful tool to compare the results of clipping and coiling of aneurysms using CTA or MRA.

FIG 1.

Illustrative cases from the portfolio of CTA clipped or MRA coiled aneurysms for each grade. The left MCA (A), anterior communicating artery (B), and right MCA (C) are CTA examples of clipped aneurysms, while the left superior cerebellar artery (D), basilar tip (E), and left MCA (F) are MRA examples of coiled aneurysms. Grade 1 (A and D): complete occlusion; grade 2 (B and E): residual neck (<2 mm using visual estimation only); grade 3 (C and F): residual aneurysm.

FIG 2.

Total number of follow-up management choices (n = 1440) per chosen grade of aneurysm residuum. A choice or judgment is defined as a rater’s choice of grade and clinical follow-up management for a selected treated aneurysm. FU indicates follow-up.