The natural history of AVM hemorrhage in the posterior fossa: comparison of hematoma volumes and neurological outcomes in patients with ruptured infra- and supratentorial AVMs

Abstract

Object: Patients with posterior fossa arteriovenous malformations (AVMs) are more likely to present with hemorrhage than those with supratentorial AVMs. Observed patients subject to the AVM natural history should be informed of the individualized effects of AVM characteristics on the clinical course following a new, first-time hemorrhage. The authors hypothesize that the debilitating effects of first-time bleeding from an AVM in a previously intact patient with an unruptured AVM are more pronounced when AVMs are located in the posterior fossa.

Methods: The University of California, San Francisco prospective registry of brain AVMs was searched for patients with a ruptured AVM who had a pre-hemorrhage modified Rankin Scale (mRS) score of 0 and a post-hemorrhage mRS score obtained within 2 days of the hemorrhagic event. A total of 154 patients met the inclusion criteria for this study. Immediate post-hemorrhage presentation mRS scores were dichotomized into nonsevere outcome (mRS ≤ 3) and severe outcome (mRS > 3). There were 77 patients in each group. Univariate and multivariate logistic regression analyses using severe outcome as the binary response were run. The authors also performed a logistic regression analysis to measure the effects of hematoma volume and AVM location on severe outcome.

Results: Posterior fossa location was a significant predictor of severe outcome (OR 2.60, 95% CI 1.20-5.67, p = 0.016) and the results were strengthened in a multivariate model (OR 4.96, 95% CI 1.73-14.17, p = 0.003). Eloquent location (OR 3.47, 95% CI 1.37-8.80, p = 0.009) and associated arterial aneurysms (OR 2.58, 95% CI 1.09, 6.10; p = 0.031) were also significant predictors of poor outcome. Hematoma volume for patients with a posterior fossa AVM was 10.1 ± 10.1 cm(3) compared with 25.6 ±28.0 cm(3) in supratentorial locations (p = 0.003). A logistic analysis (based on imputed hemorrhage volume values) found that posterior fossa location was a significant predictor of severe outcome (OR 8.03, 95% CI 1.20-53.77, p = 0.033) and logarithmic hematoma volume showed a positive, but not statistically significant, association in the model (p = 0.079).

Conclusions: Patients with posterior fossa AVMs are more likely to have severe outcomes than those with supratentorial AVMs based on this natural history study. Age, sex, and ethnicity were not associated with an increased risk of severe outcome after AVM rupture, but posterior fossa location, associated aneurysms, and eloquent location were associated with poor post-hemorrhage mRS scores. Posterior fossa hematomas are poorly tolerated, with severe outcomes observed even with smaller hematoma volumes. These findings support an aggressive surgical posture with respect to posterior fossa AVMs, both before and after rupture.

Keywords: ARUBA = A Randomized Trial of Unruptured Brain AVMs; AUROC = area under the receiver operating characteristic; AVM = arteriovenous malformation; MICE = multiple imputation by chained equations; Spetzler-Martin grade; arteriovenous malformation; infratentorial; mRS = modified Rankin Scale; microsurgical resection; posterior fossa; supplementary grade.

Fig. 1

Predictions produced by a 10-fold cross-validation technique for the multivariate model generated an area under the receiver operating characteristic (AUROC) curve of 0.64 (95% CI 0.55–0.74).

Fig. 2

Comparison of hematoma volume in patients with posterior fossa and supratentorial AVMs. The box and whiskers plots show the median values with interquartile range and minimum and maximum values (whiskers). The corresponding mean volumes (± SD) were 10.1 ± 10.1 cm³, and 25.6 ± 28.0 cm³. The difference was statistically significant (•) for supratentorial locations (p = 0.0033). Hem Vol = hematoma volume