Low cerebral blood flow and perfusion reserve induce hyperperfusion after surgical revascularization: Case reports and analysis of cerebral hemodynamics

Background: Hyperperfusion syndrome after surgical revascularization is a rare complication and there has not been any systematic study on factors that induce hyperperfusion after surgery. In this paper, we retrospectively analyzed the factors related to this syndrome. PATIENTS AND METHODS: We performed 46 cases of surgical revascularization including 33 cases of carotid endarterectomy (CEA) and 13 cases of superficial temporal artery- middle cerebral artery (STA-MCA) anastomosis during the past 5 years. Among these, we encountered three cases of hyperperfusion syndrome despite well- controlled blood pressure postoperatively. To evaluate factors related to the occurrence of hyperperfusion syndrome, we examined four parameters: (1) regional cerebral blood flow (rCBF), (2) the increase in the ratio of the postoperative rCBF compared to the preoperative rCBF (increase ratio), (3) cerebral perfusion reserve presented by the increase of rCBF after acetazolamide administration (ΔrCBF), and (4) the difference in mean blood pressure between the preoperative and postoperative state (ΔBP). RESULTS: Preoperative rCBF was significantly lower in cases of hyperperfusion syndrome than the control cases (p < 0.01 Mann-Whitney U-test). Moreover ΔrCBF was evidently lower in the hyperperfusion cases than the control (p < 0.05 Fisher's exact method). However, there was no significant difference in the ΔBP between the hyperperfusion cases and the control cases. Conclusion: In cases of marked low perfusion (low rCBF) with poor perfusion reserve (low ΔrCBF), hyperperfusion after surgical revascularization can occur even if blood pressure is adequately controlled.