Kuybu Okkes, Tadi Prasanna, Dossani Rimal H.
LSUHSC Shreveport
Asram Medical College, Eluru, India
A solid understanding of the pathophysiology of a posterior cerebral artery (PCA) stroke as well as the syndrome relating to it, requires adequate knowledge of the structures and vascular anatomy of the brain. Anterior and posterior circulations provide the primary blood circulation of the brain. Both circulations are connected by the posterior communicating arteries (PCOM), which make up the circle of Willis. When there is an occlusion in the cerebral vasculature, the circle of Willis, as well as collateral circulations, provide blood to the occluded areas. Posterior circulation is supplied by the vertebral arteries (VA), posterior inferior cerebellar arteries (PICA), basilar artery (BA), anterior inferior cerebellar arteries (AICA), pontine branches of the basilar artery, superior cerebellar arteries (SCA), PCA, and PCOM. The VAs arise from the subclavian arteries and fuse into the BA within the cranium. The BA typically divides into PCAs near the pituitary stalk at the pontomesencephalic junction. PCAs can originate from BA 70 percent of the time, 20 percent of the time from PCOMs, and 10 percent of the time from a mix of the two. The PCAs then give off branches to the midbrain, subthalamic nucleus, basal nucleus, thalamus, temporal, occipital, and occipitoparietal cortices (See Figure). PCA is divided into four segments, P1 to P4. The segments can be further categorized into deep and superficial segments or proximal and distal, respectively. P1 and P2 segments are deep segments. The P1 segment is between the termination of the BA and the PCOM. The thalamic-subthalamic arteries derived from the P1 segment supply the paramedian parts of the upper midbrain and thalamus. The tuberothalamic arteries usually arise from the PCOM and supply the anterior and anterolateral parts of the thalamus. Both sides of the thalamus and midbrain can be supplied by an Artery of Percheron (AOP), which is a rare anatomic variation. AOP arises from proximal P1. The other branches of the P2 segment include thalamogeniculate arteries and the posterior choroidal arteries. The thalamogeniculate arteries supply the ventrolateral part of the thalamus. The posterior choroidal arteries supply the lateral geniculate body, pulvinar, posterior thalamus, hippocampus, and parahippocampal gyrus. . P3 and P4 are superficial segments. The P3 segment is the quadrigeminal segment. Anterior and posterior inferior temporal arteries arise from the P3 segment. The P4 segment is the cortical segment within the calcarine fissure and became the calcarine artery. Other branches include the occipitotemporal and occipitoparietal arteries.
要扎实理解大脑后动脉（PCA）卒中的病理生理学及其相关综合征，需要充分了解大脑的结构和血管解剖。前循环和后循环构成了大脑的主要血液循环。这两个循环通过后交通动脉（PCOM）相连，后交通动脉构成了Willis环。当脑血管发生阻塞时，Willis环以及侧支循环会为阻塞区域供血。后循环由椎动脉（VA）、小脑后下动脉（PICA）、基底动脉（BA）、小脑前下动脉（AICA）、基底动脉的脑桥分支、小脑上动脉（SCA）、大脑后动脉（PCA）和后交通动脉（PCOM）供血。椎动脉发自锁骨下动脉，在颅内汇合成基底动脉。基底动脉通常在脑桥中脑交界处靠近垂体柄处分为大脑后动脉。大脑后动脉70%起源于基底动脉，20%起源于后交通动脉，10%起源于两者混合。然后，大脑后动脉向中脑、丘脑底核、基底核、丘脑、颞叶、枕叶和枕顶叶皮质发出分支（见图）。大脑后动脉分为P1至P4四个节段。这些节段可进一步分别分为深节段和浅节段或近节段和远节段。P1和P2节段为深节段。P1节段位于基底动脉末端和后交通动脉之间。起源于P1节段的丘脑-丘脑底动脉供应中脑上部和丘脑的旁正中部分。丘脑结节动脉通常起源于后交通动脉，供应丘脑的前部和前外侧部分。丘脑和中脑的两侧可由Percheron动脉（AOP）供血，这是一种罕见的解剖变异。Percheron动脉起源于P1近端。P2节段的其他分支包括丘脑膝状体动脉和脉络膜后动脉。丘脑膝状体动脉供应丘脑的腹外侧部分。脉络膜后动脉供应外侧膝状体、丘脑枕、丘脑后部、海马和海马旁回。P3和P4为浅节段。P3节段为四叠体节段。颞叶前下动脉和颞叶后下动脉起源于P3节段。P4节段是距状裂内的皮质节段，成为距状动脉。其他分支包括枕颞动脉和枕顶动脉。
