Microsurgical anatomy of the posterior cerebral artery

✓ In order to define the microsurgical anatomy, 50 posterior cerebral arteries (PCA's) were examined using × 3 to × 40 magnification. The PC A was divided into four segments: Pt was the segment proximal to the posterior communicating artery (PCoA); P 2 extended from the PCoA to the posterior margin of the midbrain and was subdivided into an equal anterior (P 2 A) and posterior (P 2 P) half; P 3 began at the posterior midbrain, ran within the quadrigeminal cistern, and ended at the anterior limit of the calcarine fissure. The PCA had three types of branches: 1) cortical branches to the cerebrum; 2) central branches to the brain stem; and 3) ventricular branches to the choroid plexus. The largest branches reaching the lateral surface of the cerebrum were located immediately anterior to the preoccipital notch, and in most cases were branches of the posterior temporal artery. This area offers a greater than 75% chance of finding a vessel large enough to perform a microvascular anastomosis. The central branches were of two types: 1) direct perforating, and 2) circumferential. The direct perforating branches arising on P 1 were the posterior thalamoperforating arteries. The “thalamogeniculate artery,” the vessel said to be occluded in the “thalamic syndrome,” was also of the direct perforating type, but it was a series of small arteries arising from P 2 A and P 2 P rather than being a single vessel. The circumferential arteries usually arose from P 1 and encircled the midbrain providing branches as far posteriorly as the colliculi. The branches to the choroid plexus were the medial and lateral posterior choroidal arteries; the former usually arose from P 2 A and entered the roof of the third ventricle, and the latter arose as a series of arteries from P 2 P and passed over the pulvinar to enter the lateral ventricle.