Posterior Choroidal Arteries

Posterior Medial and Lateral Choroidal Arteries
Stereo Lateral; Red=posterior lateral choroidal; Orange=posterior Medial choroidal (bilateral are seen on the left image)
Posterior choroidal arteries with anastomosis near foramen of Monro, and associated thalamoperforating branches
Dominant posterior medial choroidal artery.  The hemodynamic balance of the posterior medial and lateral choroidal arteries can be shifted in either direction.  The dominant vessel traverses the foramen of Monro to supply the choroid plexus of the correspondingly hypoplastic feeder.  In this example, the medial choroidal (red) is dominant and extends superolaterally across the foramen of Monro point (yellow) to supply the lateral ventricular territory (orange).  A hypoplastic lateral choroidal artery (black) is present.  The splenial arteries are labeled in purple. 
Posterior Lateral Choroidal Artery and Thalamoperforating arteries supplying a left thalamic AVM.
The anterior thalamus near foramen of Monro is usually supplied by an anteromedial perforator coming off the posterior communicating artery, as is seen in this case.  A ruptured AVM with a pseudoaneurysm (green) arising from an anterior thalamic perforator (yellow) supplies the lesion together with the posterior medial choroidal artery (blue) and posterior thalamic artery (red).  These arteries and psedoaneurysm can be identified with high degree of certainty on a pre-angiographic post-contrast MRI T1 gradient echo sequence (MP-RAGE in this case). 
Variant supply of third ventricle choroid plexus and sequential identification
Having a series of images through which an arterial course and corresponding parenchymal and venous phases can be traced is very useful when questions of identity arise.  Here, variation in foramen of Monro supply is present with distal origin of a branch coursing through velum interpositum (yellow) to reach foramen of Monro, with a hypoplastic medial choroidal artery.  The lateral choroidal system (red) is well developed. Parenchymal and venous phases help identify the choroidal blush and venous counterparts of the arterial vessels, increasing one’s confidence in correctly identifying the anatomy.
Red=psterior lateral choroidal; yellow=fornix/choroidal branch in velum interpositum; purple=choroidal blush of the lateral (higher) and third ventricle (lower and anterior to the lateral ventricular blush); light and dark blue=internal cerebral vein
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