Presentation
Past medical history of hypertension and Parkinson's disease who presents as a transfer to our tertiary care institution with concern for subarachnoid hemorrhage vs intracerebral hemorrhage. Patient received repeat imaging on arrival to tertiary care institution.
Patient Data
The different projections of CTA demonstrate an approximately 9 mm aneurysm originally thought to arise from the left proximal cavernous segment of the internal carotid artery (ICA). A DSA is needed for further clarification.
On DSA, there is no evidence of ruptured intracranial aneurysm and no clinoid/supraclinoid left ICA aneurysm. A persistent trigeminal artery (PTA) is demonstrated, which is the dominant supply of the basilar artery and bilateral SCA/PCAs, with reflux in the proximal diminutive vertebrobasilar system. A 7-mm multilobulated semi-saccular, semi-fusiform aneurysm involving the origin of the PTA is demonstrated.
On 3D reconstruction, a 7-mm multilobulated semi-saccular, semi-fusiform aneurysm involving the origin of the PTA is again demonstrated.
Case Discussion
In embryonic development, the trigeminal arteries connect the cavernous part of the developing internal carotid arteries (ICA) with the paired longitudinal neural arteries that will later form the basilar artery. The persistent trigeminal artery (PTA) refers to the most cephalically located trigeminal artery that remains patent past the embryonic stage. This artery is the most common embryonic connection between the carotids and basilar artery that persists post-embryonic development. The incidence of the persistent trigeminal artery is around 0.1-0.6% when imaged using magnetic resonance angiography (MRA) and digital subtraction angiography.
In a recent study of >16,000 patients using MRA, the frequency of intracranial aneurysms found anywhere in the cerebral vasculature was the same in patients with or without a PTA (4.2% with a PTA vs 3.7 +- 0.7% in the general population). This finding is in contrast with previously reported data suggesting aneurysms were more common in patients with a PTA. Within the population of patients with a PTA and an intracranial aneurysm, only around 1% developed the aneurysm of the PTA itself.
In our case study, an aneurysm formed at the origin of the PTA where it arises from the left proximal cavernous segment of the ICA. This is the most common spot for an aneurysm to form on the PTA according to a systematic review of 40 cases of PTA aneurysms in Italy. While the original location of the aneurysm was unclear after the CTA (ICA vs PTA), DSA gave evidence of an aneurysm located at the origin of the PTA. As the patient’s presenting symptoms stabilized, no further surgical treatment was pursued and the patient was discharged from the hospital.