Findings:
There is a conical protuberance from the basilar artery at the origin of the left superior cerebellar artery, likely in keeping with an infundibulum.
Fetal origin of the left posterior cerebral artery is seen. Hypoplastic right V4-segment is noted.
The Circle of Willis is otherwise normal.
The dural venous sinuses are normal.
The aortic arch has a normal appearance with conventional anatomy and no atheromatous change.
The common carotids, carotid bulbs, internal carotid and external carotid arteries have a normal appearance. No evidence of atheroma, stenosis, aneurysm or dissection is seen.
Vertebral arteries without hemodynamically significant changes.
Mild enlargement of the thyroid gland with cystic nodules in both thyroid lobes, in keeping with multinodular goitre. The soft tissue of the neck is otherwise unremarkable. No lymphadenopathy.
The lung apices are clear.
No bony abnormality is seen. The craniocervical junction and spinal canal appear patent.
Conclusion:
Focal dilatation of the basilar artery at the origin of the left superior cerebellar artery, likely in keeping with an infundibulum. No obvious evidence of any aneurysm.