Cerebral hyperperfusion syndrome resulting in subarachnoid hemorrhage after carotid artery stenting

A 64-year-old, right-handed man underwent endovascular treatment for internal carotid artery stenosis after experiencing a left-hemispheric transient ischemic attack. O-15-gas and H (2) (15) O positron emission tomography revealed slightly reduced cerebral blood flow (CBF), elevated cerebral blood volume, and severely reduced cerebral vasoreactivity in the ipsilateral hemisphere as determined by an acetazolamide challenge test. The patient underwent left carotid artery stenting (CAS) via a prefemoral approach under local anesthesia without any complications. Follow-up examinations performed 20 h postoperatively showed subarachnoid hemorrhage (SAH) and cerebral hyperperfusion syndrome (CHS) in the left frontal lobe. Although it is a relatively rare phenomenon, SAH resulting from CHS was determined to be specifically caused by CAS. In this case, the causes of SAH may have been related to multiple factors including increased regional CBF, loss of cerebrovascular autoregulation, contrast agent-mediated disruption of major cerebral vessels, and strong antiplatelet therapy.