See the previous post for the first part of this case.
You decide to perform surgery on the gentleman described in the previous case. The surgery goes smoothly without any immediate complications. One week after the surgery, however, he begins having unilateral headache on the same side as the surgical repair, improved with upright position. Then, he has two episodes of focal motor seizures, witnessed, followed by a stroke with CT evidence of intracerebral hemorrhage. Imaging of the vessel itself does not show thrombosis or restenosis. This is not hemorrhagic conversion from an embolic stroke.
Challenge: What happened? What is this syndrome called? What is the pathophysiology?
Image is in the public domain.