Anterior Choroidal Artery
For a fuller discussion, see dedicated neuroembryology section. For a masterful description, consult Lasjaunias and Berenstein’s work “Surgical Neuroembryology”, either 1st edition volume 3 or 2nd edition volume 1.
The anterior choroidal artery is almost as old as hills. Phylogenetically, its homologs (recorded under various confusing names in dissections of “lower” species) are already well developed in fishes and continue into amphibians and mammals. In these species, it supplies the ever enlarging posterior hemispheres, in effect vascularising the territory of the posterior cerebral artery in the human. This is because the posterior circulation does not begin to supply “supratentorial brain” until late in evolution when (probably) growing volume of the brain places increasing demand on additional vascular supply sources. As the posterior cerebral artery is annexed by the vertebrobasilar system in relatively advanced mammals, the role of the anterior choroidal artery in hemispheric supply diminishes.
In the human embryo, the anterior choroidal is quite prominent at the “choroidal” stage of development (roughly 5 weeks or so) when the vertebrobasular system has not yet come to be and the carotid artery supplies almost the entire brain, including upper brainstem. As the hemispheres grow, the volume of brain supplied by the anterior choroidal diminishes in favor of the posterior cerebral artery. This explains why in some individuals the anterior choroidal artery retains portions of cortical PCA territory (see below). This has led to numerous erroneous angiographic and surgical reports of “duplicated PCA” based on appearance of two large vessels coming off the distal ICA. Likewise, perforator vessels can come from either proximal choroidal or just distal to it, from the ICA proper. It is critical to understand that this, too, is an error — there is only one PCOM, and only one anterior choroidal possible — choroidal being the vessel that supplies choroid plexus. However, even in its “normal” relatively small state, the anterior choroidal enjoys importance far out of proportion to its size.
The A. Chor. ostium is usually seen on 1.5T MRA, but the rest of the vessel is seldom visualized unless significant pathology exists to enlarge it. In contrast, both cisternal and choroidal portions of normal-size anterior choroidal arteries are nearly always on 3T MRA. All of these studies have to be of high quality.
3-Tesla MRA of normal anterior choroidal arteries (red)
1) Ostium of the A Choroidal artery lateral and distal to the PCOM (blue)
2) Cisteral portion of the A Chor
3) Lateral course in the perimesencephalic cistern at level of PCOM / PCA confluence. Even medial choroidal artery (orange) can be seen on a 3-T
4) Entrance into the choroidal fissure
5) In the choroidal fissure, in plane of scan
6) Branching to feed choroid plexus
In contrast to 3T, the 1.5T MRA below only shows an ostium of what is in fact a very prominent anterior choroidal artery (red), as seen on angio of the same patient. Poor visualization is to some extent related to direction of Anterior Choroidal flow, which can be close to plane of MRA slab.
However, we do not stop there. Here’s what 7T can produce. Pretty stunning. The Anterior Choroidal (light blue) can be traced perfectly well towards the choroid plexus (dark red). Gadolinium contrast was administered prior to the scan, which explains some venous structures in there (not labeled). Notice amazing views of the lateral lenticulostriates (black), thalamogeniculate (dark blue double-sided arrow), as well as posterior choroidal (white), posterior inferior temporal (green) and middle inferior temporal (pink). The tentorium cerebelli enhancement (yellow) is also very helpful, as best seen in stereo
The same image in cross-eye stereo. Notice the graceful fall of the tentorium cerebelli, separating branches of the PCA and the SCA. Can you see the junction of the medial septal and thalamostriate veins?
Anterior Choroidal Artery Anatomy and Landmarks
The course of anterior choroidal artery cisternal segment in the paramesencephalic cistern (around the cerebral peduncles) is superimposed angiographically upon the middle segment of the basal vein of Rosenthal. This can be demonstrated on a single image by selecting the arterial phase of the injection to be the “mask” of a later venous phase
In the stereo projections above, where “mask” arteries appear white, a prominent Ant. Chor. artery is superimposed upon the basal vein. The patient suffers from NFII with multiple meningiomas. Notice many tiny branches (red arrows) coursing superiorly from the Anterior Choroidal artery (best seen in the “normal” image below marked with red arrows).
Anterior Choroidal perforators 2
Another illustration of anterior choroidal perforators (purple) coming off the main trunk (red) prior to the plexal point (light blue). A branch to the choroid distal to the plexal point may be present also (pink). The PCOM is orange (with a large thalamic branch of its own). MHT (dark blue) and ILT (green) branches are also visible.
If you talk to an open vascular surgeon, they will tell you about duplicated or multiple choroidal arteries. Essentially what they are seeing are several vessels arising distal to the PCOM and looking like they are heading into choroidal territory. While it is certainly a correct observation that more than one vessel can be seen in the choroidal region, there is only one choroidal artery — meaning the artery that supplies the choroid plexus. What is really going on is that perforator vessels which normally arise from the cisternal (proximal) portion of the anterior choroidal artery can sometimes as a variant arise directly from the adjacent internal carotid artery. These distal vessels are pretty much all eloquent. They are also the same vessels that hypertrophy to provide anastomoses between the choroidal perforator system and the lenticulostriate vessels in Moya-Moya. Here is an example of multiple normally proximal choroidal artery perforators arising as a variant directly from the ICA. Perforators are marked by red arrows. Choroidal artery proper is purple, including its choroidal segment (white). PCOM is yellow. Case courtesy Dr. David Gordon
Typical appearance of an anterior choroidal artery in stereo.
Typical appearance of the anterior choroidal artery (red). The red arrow marks the plexal point where the artery enters the choroidal fissure. A small artery distal to the anterior choroidal is present also (orange) These arteries ascend thru the anterior perforated substance and may supply areas of hypothalamus or optic tract — these are the arteries which hypertrophy in the moya-moya condition. An MHT branch is also present (blue)
Anterior Choroidal Projection — RAO projection (about 80-60 degrees RAO) of the RIGHT Anterior choroidal artery usually elevates the MCA branches away from the choroidal.
Frontal projection — the best projection for choroidal aneurysm is usually an ipsilateral oblique and somewhat submental. It is particularly good for visualizing choroidal artery origin when associated with an aneurysm. For example, in this case the optimal coiling view of this left choroidal aneurysm is a steep left anterior oblique, somewhat Waters.
Red=A. Chor; Purple=plexal point; Yellow=choroidal segment
It is basic knowledge that infarcts of the anterior choroidal artery can lead to hemiplegia, due to its participation in supply of the posterior limb of the internal capsule. Other potential deficits include various homonymous field cuts (optic tracts, lateral geniculate), hemisensory deficits (lateral thalamus), non-primary motor movement changes, such as relief of rigidity and less often tremor from classic surgical ligations of the choroidal artery in patients with Parkinson’s disease (globus pallidus interna and ansa reticularis). As with other vessels, the clinical syndrome of anterior choroidal artery occlusion will be determined by 1) size of territory supplied by the choroidal in each individual case, which is highly variable and 2) availability of collateral support. There is definite value to memorizing the structures which could be potentially supplied by the artery, but it is silly to expect choroidal occlusions to produce a particular deficit related to one of these areas. Some choroidal occlusions are nearly asymptomatic, while others can be devastating, for the above reasons. More details on choroidal artery distribution can be seen below, including examples of when the choroidal persists in supply of the posterior temporal territory that is normally annexed by the PCA.
In the following patient with a ruptured perinidal choroidal aneurysm, global and microcatheter injections demonstrate the more typical course of the distal choroidal artery, just proximal to its plexal point, through the expected region of the posterior limb of the internal capsule.
A post-nBCA CT scan confirms the course of the vessel through the posterior limb, with the index hemorrhage
Anterior Choroidal-PCOM confusion
One of the more embarrassing and potentially hemiparetic misidentifications is to mistake the anterior choroidal for a PCOM. This is especially critical in surgical cases, where a PCOM aneurysm may be treated by sacrifice of the PCOM (unless it turns out to be the anterior choroidal)
The anterior choroidal is labeled in red, whereas a small PCOM, arising more proximally, is marked with orange arrows. On the AP, you can see the hemispheric portion of the A Chor in red, and the choroidal portion in purple.
Anterior Choroidal Artery capturing PCA cortical territory
As a consequence of embryonic participation of the choroidal artery in supply of cortical territory in many mammal species, there is occasionally encountered a variant whereby the choroidal artery supplies the territory typically served by the Posterior Cerebral Artery. The most commonly encountered variant captures territory of the inferior temporal branch, which supplies the undersurface of the temporal lobe. The parieto-occipital and calcarine branches typically originate from their “usual” positions. It is important not to confuse this variant with by thinking of it as a “duplicated PCOM, or duplicated choroidal”. There can be only one PCOM and one choroidal. Here are MRA and angio examples from same patient
Red=PCOM/PCA; Yellow=Anterior Choroidal Artery
Another example, courtesy Dr. Howard A. Riina, with temporal branch labeled with black arrows
Cross-eye stereo lateral
Frontal cross-eye stereo
Vertebral artery injection shows lack of inferior temporal branch on right, which is present on the left (black arrow)
Another example, with an aneurysm. It is critical not to mistake this choroidal aneurysm for a PCOM — surgical or endovascular sacrifice of PCOM ostium with a good P1 backfilling it is very well tolerated. Choroidal sacrifice is a different story. There are plenty of examples of the latter.
Here is a vert injection — notice that inferior temporal branches are missing on the left (normal ones inside oval on right)
Global frontal and lateral views on top, cross-eye stereos on bottom
Lateral oblique. Typical course of the choroidal artery (black arrow). There is no “wash-in” from P1 segment — tells you that that either this should be a fetal PCOM, or that this is a choroidal. Several perforators are seen coming off choroidal (white arrows) and one separately from the more distal ICA (dashed white arrow). Do not confuse this for “duplicated anterior choroidal artery” — there is no such thing . By definition a choroidal artery is one that goes to choroid plexus — the rest are perforators off ICA — they may be eloquent, but they are not the choroidal artery. The posterior inferior temporal branch is marked by dashed black arrow. Middle inferior branch by open black arrow.
Anaglyph VR stereo
Hard to figure out on MRA prospectively, but it is there, separate PCA (black) and choroidal (white). No PCOM
Common trunk PCOM and Anterior Choroidal
Super rare. But very real. And can be extremely clinically important as well — again, not to mistake an anterior thalamoperforator for choroidal artery — both are eloquent of course but in very different ways.
Presentation is SAH. Cause is a tiny aneurysm at the bifurcation of common origin PCOM (black arrows) and choroidal (white arrows). Dont see the aneurysm — its very tiny indeed and superimposed on the PCOM in this straight lateral
Here it is (white arrowhead), in an oblique view. Pretty neat diagnosis, huh?
The aneurysm is clipped. Despite best efforts, the choroidal is lost (image on right). However, the patient is asymptomatic 🙂
Why? The choroidal backfills via the posterior lateral choroidal system! Extremely rare for collateral to actually rescue the choroidal — but here it is…
Look at the vessels side by side. What a great case!
According to Lasjaunias, as illustrated by Dr. Clarencon, the embryologic mechanism responsible for common pcom/choroidal origin is related to persistence of some less typical anastomoses between PCOM and Choroidal vasculature, is as follows:
Choroidal is white arrow
Another super rare variant, also explained by embryology above. Cases below courtesy Dr. Eytan Raz
In this very rare variant, there is a connection between choroidal and PCA at the level of P2. How to think of it? It is on the spectrum of choroidal persistence in supply of PCA territory — part PCA is from choroidal, part from PCOM/P1 — except that there is a connection between the two at P2 segment.
There is a small left P1 (white arrow). The right ICA is “normal”. Left ICA standard projections are also unrevealing
Oblique lateral projection view of left ICA – PCOM is white arrow, proximal choroidal is dashed arrow, distal choroidal is ball arrow, connection between choroidal and PCOM origin PCA is arrowhead. Distal PCA branches are open arrows. Clearly there is a choroidal-PCOM “ring”
Volume rendered image, same case
Another case of same, on CTA, also courtesy Dr. Eytan Raz
PCOM (arrow) and choroidal (dashed arrows) fusion at P2 segment (open arrow) to produce a slightly larger caliber PCA (arrowhead)
Volume Rendered image of same. The PCOM is very faint and thus really cant be seen here. But, there is a nice ACOM fenestration 🙂
Anterior Choroidal origin proximal to PCOM
According to theory, anterior choroidal artery can never be proximal to the PCOM — the latter being the caudal ramus of the internal carotid artery (see neuroembryology). However, sometimes it just does, like in the example below, right? NO!! Fake! Below is a particularly convincing fakeout.
Loot at this frontal view, and you will understand. The choroidal below is labeled in RED
Proximal Anterior Choroidal=red; Choroidal segment of Ant. Chor = white; Parenchymal Ant. Chor. branches = yellow; PCOM=orange
AP and Lateral views (Stereo pair on top) of a temporal lobe avm with deep anterior choroidal supply component.
Anterior Choroidal – Posterior Lateral Choroidal anastomosis — the anterior choroidal beyond the plexal point supplies the plexus of the temporal horn, where it is in balance with the posterolateral choroidal going to the atrium region. This is elegantly shown in the following case of left choroidal plexus AVM, supplied by both vessels with beautiful illustration of draining veins.
Red=anterior choroidal; yellow = posterolateral choroidal; pink=choroidal vein; light blue=inernal cerebral vein; brown=basal vein to sylvian veins; dark blue = atrial vein; white = superior petrosal sinus; green = midbasilar agenesis
Irving S. Cooper M.D. SURGICAL ALLEVIATION OF PARKINSONISM: EFFECTS OF OCCLUSION OF THE ANTERIOR CHOROIDAL ARTERY. Journal of the American Geriatrics Society Volume 2, Issue 11, pages 691–718, November 1954