gms | German Medical Science

Objective: Giant intracranial aneurysms of the posterior circulation (GPCirA) often cause compression of the brainstem and adjacent structures, resulting in neurological deficits. Using data from the Giant Intracranial Aneurysm (GIA) Registry, we designed a study to investigate potential predictors of cranial nerve deficits (CND), motor deficit and the modified Rankin Score (mRS) in subjects with GPCirA.

Methods: All data were extracted from the database of the GIA Registry, which is an international multicenter prospective observational study exclusively focusing on intracranial aneurysms with diameters of at least 25mm. In magnetic resonance imaging of 30 subjects with unruptured GPCirA we examined GPCirA volume, presence of partial thrombosis (PT), PT volume and the amount of displacement of the brainstem as measured by the distance between the McRae Line and the tip of GPCirA (∆MT), as exemplified in figure 1 [Fig. 1].

Results: 30 GPCirA in 30 subjects were included. The prevalence of CND was 50%. In univariate analysis, subjects with CND were significantly younger (51y, IQR 15.0) and showed larger ∆MT (50.7mm, IQR 14.7) compared to those without CND (69.0y, IQR 21.0; p=0.011; 39.0mm, IQR 13.6; p=0.02). No differences were observed between the CND groups in sex, GPCirA volume or PT. The prevalence of motor deficit was 33.3%. Patients with motor deficit different from those without motor deficit in ∆MT (50.5 mm IQR 13.8 vs 39.1mm IQR 17.7; p=0.04) and the prevalence of PT (80.1% IQR 27.4 vs 91.7% IQR 15.8; p=0.03). Patients with poor mRS (3-5) showed significantly larger GPCirA volumes (14.9 cm3, IQR 10.6) compared to those with good mRS (0-2) (6.8 cm3, IQR 7.4; p=0.03). In multivariate regression analysis, the occurrence of CND was predicted only by ∆MT (OR 1.1 (95% CI 1.0-1.2); p=0.04), but not by GPCirA volume. Poor mRS was associated withGPCirA volume (OR=1.2 (1.0-1.4); p=0.04), but not with ∆MT. Motor deficits were not predicted by any of the examined factors. There was no correlation between GPCirA volume and ∆MT (rs=0.01; p=0.96).

Conclusion: Our findings suggest that there is no direct link between GPCirA volumes and the amount of brainstem displacement away from the cranial base. While the degree of brainstem displacement predicted the prevalence of CND, GPCirA volumes predicted patient disability. Our results support the notion that the morbidity of GIA not only depends on GIA size but also on the location of mass effect on surrounding structures.