Risk factors predicting a higher grade of subarachnoid haemorrhage in small ruptured intracranial aneurysm (< 5 mm)

To identify the risk factors for clinical and radiographic grades of subarachnoid haemorrhage (SAH) in small (< 5 mm) intracranial aneurysms (SIAs).

We retrospectively analysed patients with SIAs treated in our centre between February 2009 and June 2018. The clinical status was graded using the Hunt and Hess (H&H) score and the radiological severity of SAH was graded by Fisher grades (FG). The risk factors were determined using multivariate logistic regression analysis.

A total of 160 patients with ruptured SIAs (< 5 mm) were included. In univariate analysis, smoking (P = 0.007), alcohol use (P = 0.048), aspirin use (P = 0.001), and higher size ratio (SR) (P = 0.001) were significantly associated with a higher H&H grade (3-5) in SIAs; and smoking (P = 0.019), aspirin use (P = 0.031), inflow angle < 90 degrees (P = 0.011), and aneurysm size (P = 0.039) were significantly associated with a higher FG score (3-4). In the adjusted multivariate analysis, previous SAH (OR, 12.245, 95% CI, 2.261-66.334, P = 0.004), aspirin use (OR, 4.677, 95% CI, 1.392-15.718, P = 0.013), alcohol use (OR, 3.392, 95% CI, 1.146-10.045, P = 0.027), inflow angle < 90 (OR, 3.881, 95% CI, 1.273-11.831, P = 0.017), and higher SR (OR, 6.611, 95% CI, 2.235-19.560, P = 0.001) were independent risk factors for a higher H&H grade in ruptured SIAs; smoking (OR, 2.157, 95% CI, 1.061-4.384, P = 0.034), and inflow angle < 90 degrees (OR, 2.603, 95% CI, 1.324-5.115, P = 0.006) were independent risk factors for a higher FG (3-4).

This study revealed that inflow angle < 90 degrees and size ratio, but not absolute size, may highly predict poorer grade of SAH in SRA. Aspirin use, previous SAH, and alcohol use were significantly associated with a higher H&H grade in ruptured SIAs, and smoking was a significant predictor of poorer FG.