2024年5月28日 · A1: horizontal or pre-communicating segment. originating from the terminal bifurcation of the internal carotid artery, extending ~14 mm in length. terminates at the anterior communicating artery. A2: vertical, post-communicating or infracallosal segment

2024年5月28日 · Anterior cerebral artery hypoplasia or absence (aplasia) is an uncommon anatomical variant involving the first portion (A1 segment) of the anterior cerebral artery. The artery may be underdeveloped, as in hypoplasia, or completely absent, as in aplasia.

There is non-visualization of the A1 segment (pre-communicating) of the right anterior cerebral artery. The left A1 is prominent and gives off the tortuous anterior communicating artery as well as both A2 (post-communicating) segments.

Hypoplasia of the right A1 segment is compensated by dominance of the left A1 segment that supplies the right A2 segment, via the anterior communicating artery.

2024年3月20日 · A1 segment: ~2%. A2 segment: ~2% (autopsy series) anterior communicating artery: ~5%. middle cerebral artery fenestration: <1%. posterior cerebral artery: rare. basilar artery fenestration: ~0.6%. vertebral artery: ~1%

2023年4月15日 · ACA territory infarcts are less common because if the A1 segment is occluded there is generally enough collateral flow via the contralateral A1 segment to supply the distal ACA territory 2. Embolic strokes (often with MCA involvement) are the most common cause 3 .

Aplastic right A1. Case Discussion Nice example of a common variant of the circle of willis where the right A1 is tiny and the right A2 is supplied by a large Acom.

The CTA with 3D-VR shows a saccular aneurysm of the anterior cerebral artery (A1 or pre-communicating segment) measuring (8 x 6 mm) with a narrowed neck measuring 2 mm. The remainder of the arterial circle of Willis is unremarkable. No subarachnoid hemorrhage is seen.

Two normal variants of the anterior cerebral artery are illustrated in this case, Azygous anterior cerebral artery and hypoplastic A1 segment.

Diagnostic angiography 11 x 7 x 4 mm, daughter aneurysms, broad necked, arising from dominant left A1 segment. Right A1 segment is aplastic. Questionable area involving the right P1 of either dysplastic segment versus very small bleb aneurysm, worthy of follow up.