Contrast extravasation on computed tomographic angiography mimicking a basilar artery aneurysm in angiogram-negative subarachnoid hemorrhage: report of 2 cases.

BACKGROUND AND IMPORTANCE: Contrast extravasation on computed tomography angiography (CTA) is becoming more common, with increasing use of CTA for myriad intracranial vascular pathologies. This article describes the first 2 documented cases of contrast extravasation from a nonaneurysmal basilar artery source seen on CTA and discusses possible pathophysiologic mechanisms. CLINICAL
PRESENTATION: We present 2 cases of diffuse atraumatic subarachnoid hemorrhage in which the CTA showed an abnormality in association with the basilar artery highly suggestive of a ruptured aneurysm. Follow-up digital subtraction angiography, however, was completely negative. Subsequent repeat digital subtraction angiography failed to reveal a vascular lesion. Both patients were treated for complications associated with SAH, but given the negative digital subtraction angiography, no intervention was performed.
CONCLUSION: Because of the frequent use of CTA, contrast extravasation is an increasingly common observation. Physicians should be aware that basilar artery extravasation can mimic the appearance of an aneurysm.