The value of radio-anatomical features on non-contrast CT scans in localizing the source in aneurysmal subarachnoid haemorrhage.

Identification of the source of subarachnoid haemorrhage (SAH) can be a challenge in the presence of multiple aneurysms. This study was carried out to assess whether radioanatomical features on noncontrast enhanced computerised tomography (CT) scans may be of value in localizing ruptured intracranial aneurysms. The diagnostic CT scans of 56 consecutive patients, investigated for SAH with cerebral angiography, over a period of six months were available for review. Various radioanatomical features were assessed: (1) pattern of subarachnoid blood (e.g. predominant site and location near major vessel bifurcation), (2) presence of intraparenchymal haematoma, (3) presence of aneurysm contour and (4) hydrocephalus. On the basis of the findings an estimation of the anatomical location of the source of bleeding was made and then compared with the angiogram findings to which the reviewer was blinded. The location of the aneurysm was correctly identified in 89.5% of cases. Careful analysis of the pattern of bleeding was essential for the successful localization of the aneurysm in all these cases. The presence of an aneurysm contour was also associated with correct identification of the source of bleeding (chi(2) = 6.067, P = 0.02). Our findings suggest that radioanatomical features on CT scans in SAH can be a valuable aid in the correct identification of the location of the ruptured aneurysm. This would be of particular significance in the presence of multiple intracranial aneurysms.