PCA Infarct-MRI

Clinical Data: Young adult presents with history of headache and seizures. MR shows acute  non-hemorrhagic stroke of right PCA possibly involving P-2 segment. 

Teaching points by Dr MGK Murthy

·         PCA arises from top of basilar and supplies midbrain, subthalamic nucleus, basal nucleus, thalamus, mesial inferior temporal  cortices

·         Additionally via PCOM, supplies collateral circulation to MCA territory

·         Divided by PCOM in to P1 (including thalamogeniculate ,splenial and medial as well as lateral posterior choroidal arteries) and P2 segments (posterior temporal and internal occipital)(P2A=crural cistern segment, bridges with posterior P2P Ambient cistern component)

·         P3 segment of PCA  refers to  quadrigeminal segment and P4 is cortical segment

·         Prominent Laterality of P4 segment  is   a  reliable sign of collateral circulation positivity,  from leptomeningeal anastomosis (200to 600 microns in size) M1 segment  block  of MCA , (starts in hours and peaks in days or weeks )on MRA

·         Variant include fetal PCA (absent or hypoplastic P1) (30%)and central artery of Percheron (Bilateral  ,medial thalamic and rostral midbrain perforators arise from single ,unilateral , common, P1segment)

·         Etiology of stroke are like elsewhere , with cardiogenic embolization and dissection of proximal vessels  as well as migraine(70% occur only  in patients  with aura) preferentially involving PCA