Dolichoectasia of the internal carotid artery terminus, posterior communicating artery, and posterior cerebral artery: The embryonic caudal ramus internal carotid segmental vulnerability legacy

Abstract

Dolichoectasia of the distal internal carotid artery, posterior communication artery (PCoA) and posterior cerebral artery is an extremely rare abnormality. Dolichoectasia of the internal carotid artery, PCoA and the P1 segment of posterior cerebral artery can be postulated its pathogenesis by the embryological perspective basis from caudal ramus of the internal carotid artery terminus. The pathogenesis and treatment strategy are not well established. We reviewed and proposed embryological perspective, pathogenesis, clinical setting, radiological findings and management of this rare malformation.

Keywords: Dolichoectasia; aneurysm; embryology.

Figure 1.

Simplified illustration of the embryonic stage of vascular development. At the 4th–5th week stage, the ICA branches divide into the cranial and caudal rami (a). Later, the cranial ramus of the ICA, which is a telencephalic brain artery, will give rise to the ACA, MCA, and AchA, while the caudal division remains as PCoA and later annexes to the BA. The terminal caudal ICA ramus is the future PCoA and future P1 segment of the PCA (b). Source: reproduced with permission from Elsevier.¹⁰

Figure 2.

A case of calcified dolichoectasia in the right PCoA-PCA with acute subarachnoid hemorrhage. Axial (a) non-contrasted CT scan of the brain shows acute subarachnoid hemorrhage at the right ambient cistern and tubular-like shaped calcifications at the right-sided suprasellar cistern. Axial (b) T1-weighted MR with gadolinium image shows a multi-lobulated aneurysm of the P1 segment in the right PCA and tortuous vessels. Left vertebral angiogram (c) shows dilated, elongated and tortuous at the right PCoA (arrow), which contributed to the right MCA territories (double arrows) via the residual short segment of ICA. There is right ICA occlusion, which terminates at the ophthalmic artery (not shown). Note the large, multi-lobulated aneurysm at the P1 segment of the right PCA (arrowhead). Embolization was done at the outpouching portion, which was surrounded by the subarachnoid blood detected in the non-contrasted CT scan. Coil embolization (arrowhead) was meticulous to preserve the right PCA (arrow) (d).

Figure 3.

An illustrative case of dolichoectasia in the right ICA, P1 segment of the right PCA and distal BA presenting with acute left hemiparesis. Axial (a) diffusion-weighted MR image shows acute lacunar infarction at the left cerebral peduncle. Axial (b) proton density-weighted MR image shows the significant tortuous course of the supraclinoid right ICA and fetal-type AChA (arrow). Left vertebral angiogram anteroposterior (c) view shows irregular aneurysmal dilatation, and the elongated and tortuous P1 segment of the right PCA (arrowhead) and dysplasia of the distal BA (arrow). Notably, the SCA appears normal. Right internal carotid angiogram anteroposterior (d) views show a 360-degree loop of the right supraclinoid ICA and confirmed the fetal-type AchA (arrow). The fetal-type AChA gives the terminal temporal cortical branches. The fetal-type AChA variation is rare. In general, the telencephalic embryonic branches of the AchA will annex with the P1 and become the future P2, P3 and P4 in the typical adult human pattern. In this particular case, the abluminal P1 might fail to completely annex the embryonic AchA branches. The persistent embryonic arterial pattern is one piece of evidence that links segmental dolichoectasia back to a date in early life.

Figure 4.

An illustrative case of a woman who experienced chronic headache for years and developed left third cranial nerve paresis over a month. The skull radiography lateral view (a) shows serpentine, tram-track calcification at the suprasellar region (arrow). Coronal CT angiography of the brain (b) and (c) confirms the elongated, fusiform dilated vascular wall with calcification of the P1 segment of the left PCA and supraclinoid left ICA, respectively. Left internal carotid angiogram anteroposterior view (d) shows the elongated, fusiform dilated and tortuous nature of the left distal ICA (arrow). Axial reformation 3D digital subtraction angiography (e) shows the hyostapedial variant of the left ICA (arrowhead in d and e). Left vertebral artery angiogram anteroposterior (f) view shows elongated and fusiform dilatation of the P1 segment of the left PCA, including basilar tip (arrow). The P1 segment of the right PCA supplies the right MCA territory (arrowhead) due to aplastic right ICA (image not shown).

Figure 5.

A case of dolichoectasia at the left ICA and P1 segment of the left PCA presented with acute subarachnoid hemorrhage. Axial non-contrasted CT scan (a) and axial CT angiography (b) of the brain show acute subarachnoid hemorrhage at the left-sided basal cistern and calcified left supraclinoid ICA. 3D-digital subtraction angiography reformation of the left internal carotid artery (c) shows fusiform dilatation, oblong and redundant. Left vertebral angiogram (d) shows multi-lobulated dilatation of the P1 segment of the left PCA (arrow). Post-surgical left vertebral angiogram (e) shows successful clipping (arrow). The left occipital artery–left PCA bypass is also successful (image not shown).