PICA infarction

CT-images of a left-sided PICA-infarction.
In unilateral infarcts there is always a sharp delineation in the midline because the superior vermian branches do not cross the midline, but have a sagittal course.
This sharp delineation may not be evident until the late phase of infarction.
In the early phase, edema may cross the midline and create diagnostic difficulties. Infarctions at pontine level are usually paramedian and sharply defined because the branches of the basilar arery have a sagittal course and do not cross the midline.
Bilateral infarcts are rarely observed because these patients do not survive long enough to be studied, but sometimes small bilateral infarcts can be seen.