Tapan Mehta, MBBS, MPH

Björkman J, Frösen J, Tähtinen O, Backes D, Huttunen T, Harju J, et al. Irregular Shape Identifies Ruptured Intracranial Aneurysm in Subarachnoid Hemorrhage Patients With Multiple Aneurysms. Stroke. 2017

Endovascular therapy has become the treatment of choice for the majority of ruptured saccular intracranial aneurysms (sIAs). About 15–30% of patients can present with more than one sIA. Identification of ruptured sIA could sometimes be difficult without direct visualization (micro surgically) when more than one sIA is located in close proximity to the site of the hemorrhage on the computed tomography (CT). It is important to identify the ruptured aneurysm correctly to aid definitive endovascular management. This article adds to the literature on the importance of aneurysm shape in addition to size in determining rupture status of sIAs.

A large population-based cohort of 264 patients with aneurysmal subarachnoid (aSAH) (with 713 sIAs) was studied. Amongst a total of 268 ruptured aneurysms, 96.3% were irregularly shaped and 53.7% were smaller than 7mm. The largest sIAs did not rupture in 12.5% of patients. Of these larger unruptured sIAs, 87% were smooth. The analysis of the entire study cohort showed that sIA size (OR [odds ratio], 90.3; 95% confidence interval [CI], 47.0–173.5; P<0.004) and shape (OR, 1.20 per 1 mm; 95% CI, 1.06–1.37; P<0.000) were independent predictors of sIA rupture after adjusting for age, sex, smoking, hypertension, and familial history of aneurysms.

Identification of ruptured sIA just based on hemorrhage distribution on CT without direct visualization could be a potential cause of misclassification bias. To understand the effect of this misclassification bias, a sub-analysis of only micro surgically treated patients with direct visual confirmation of ruptured sIA was also performed. This sub-analysis corroborated the predictability of shape and size in identifying ruptured sIAs (shape [OR, 43.2; 95% CI, 15.6–119.9]; size [OR, 1.24; 95% CI, 1.01–1.54]).

Consideration of aneurysm shape and size in addition to hemorrhage distribution on CT scans could significantly increase the sensitivity and specificity for identifying ruptured sIA in cases with multiple sIAs. High resolution MRI imaging to assess the rupture status (sensitivity of 98.4% and specificity of 81.9%, Nagahata et al.) has been well described. As these imaging techniques become more readily available, utilizing them in conjunction with aneurysm rupture-related risk factors would make identification of ruptured sIA impeccable in cases of aSAH with multiple sIAs.