Extracranial-Intracranial Bypass Surgery for Symptomatic Cerebral Artery Occlusion—Reply

In Reply We thank Dr Li and colleagues for their Letter about our recent study. We agree that collateral circulation is an important factor regulating cerebral blood flow. In patients with intracranial atherosclerotic disease, cerebral perfusion is determined by a complex interplay of multiple factors, such as the degree of stenosis, location, autoregulation, and collateral circulation status. CT perfusion, which uses an algorithm to quantitatively calculate the overall hemodynamic status, represents the integrated result of many factors, including collaterals. The perfusion status, instead of the collateral status, has been reported to have prognostic value in patients with symptomatic chronic occlusive cerebrovascular disease.