Ruptured "Occult" Aneurysm Disclosed by Three-Dimensional Angiographic Reconstructions

Rotational angiographic sequences and their three-dimensional reconstructions have led to major improvements in angiographic diagnostics, especially in the study of brain aneurysms. Reconstructions accurately depict the morphology of the aneurysm, namely any wall irregularities and the possible origin of arterial branches from the aneurysmal sac, and display the aneurysm on multiple spatial planes, measuring its different diameters and ratios (particularly the dome to neck ratio). Lastly, three-dimensional angiographic reconstructions will sometimes disclose ruptured or intact aneurysms not depicted by digital subtraction angiography. A 43-year-old woman was admitted to the emergency room of Maggiore Hospital, Bologna Local Health Trust, presenting severe headache, confusion and nuchal rigidity. Emergency CT scan disclosed cisternal subarachnoid haemorrhage. Subsequent 3D sequences revealed an aneurysm of the left carotid artery siphon. This occult aneurysm found in our patient had been masked by the overlying infundibular origin of the posterior communicating artery. This prevented detection of the lesion not only in standard oblique anteroposterior, craniocaudal and lateral sequences but also in the rotational sequence. Identification of the aneurysm in our patient was the result of the diagnostic strategy adopted. When cisternal subarachnoid haemorrhage is detected, our protocol routinely includes a rotational angiographic sequence centred on the anterior circulation and on the posterior circulation when the standard examination fails to depict the course of all the vessels or when the features of subarachnoid haemorrhage strongly suggest aneurysm rupture in that anatomical location. Three-dimensional angiographic reconstructions are extremely useful not only to characterize brain aneurysms, but also to disclose ruptured occult aneurysms and additional zero grade lesions.