Fusiform aneurysm of a persistent primitive trigeminal artery associated with cerebrovascular anatomic variations: a report of two cases.

There are four embryonic anastomoses that exist between the internal carotid artery (ICA) and the vertebrobasilar (VB) system, which may fail to regress postfetal life; one of which is the trigeminal artery. Other persistent anastomoses include those formed by the hypoglossal, otic and proatlantic intersegmental arteries. In addition, other cerebrovascular variations may accompany a persistent primitive trigeminal artery (PPTA); such as arteriovenous malformations, aneurysms, carotid-cavernous fistulas and stenotic cerebral vessels. We present two very rare cases of a left PPTA. In the first case, there was a past medical history significant for cervico-thoraco-lumbar spondylitis and in the second case of an operated occipital astrocytoma. In both cases, the PPTA was associated with a fusiform aneurysm located in the carotidian (lateral) aspect of the PPTA as well as other cerebrovascular anatomic variations. In the first case, the length of the PPTA was 26.0 mm and its endoluminal diameter, at its origin at the ICA, was 1.8 mm; the aneurysm has a length of 8.4 mm. In the second case, the length of the PPTA was 31.0 mm and its endoluminal diameter at its origin at the ICA was 3.0 mm; the aneurysm have a length of 7.6 mm. Identification of these variant vessels should not be ignored before planning and execution of neurosurgeries to prevent possible perioperative risks.