CT of petrous carotid aneurysms

Aneurysms arising from the petrous part of the internal carotid artery (ICA) are exceedingly uncommon. Only 21 angiographically proven cases have appeared in the literature. The CT appearance of these rare lesions has not previously been reported. In the two cases described here, the CT pattern closely resembles that of the more common petrous apex meningioma. Consideration of a petrous carotid aneurysm, when confronted with a lesion in the subtemporal region on CT scan, may have important therapeutic implications. The presence of such an aneurysm may be easily confirmed by angiographic study, averting the possibility of an ill-advised surgical procedure. Cerebral angiography is crucial to a definitive diagnosis. The precise location of the petrous aneurysms in these instances, as well as coexistence of other aneurysms at more common sites, supports the hypothesis that many intrapetrous aneurysms are congenital and develop at the site of origin of an embryologic artery.