Posterior Circulation Hyperperfusion Syndrome after Superficial Temporal Artery–Superior Cerebellar Artery Bypass for Vertebral Artery Dissection

A 68-year-old man was diagnosed with infarction of the cerebellum and medulla oblongata caused by vertebral artery dissection manifesting as severe stenosis with poor collateral flow. He underwent superficial temporal artery (STA)–superior cerebellar artery (SCA) bypass for the prevention of fatal brain stem infarction. He had consciousness disturbance 2 days postoperatively. Single-photon emission computed tomography revealed hyperperfusion in the posterior circulation. His consciousness improved as hyperperfusion improved. We report the first case of posterior circulation hyperperfusion syndrome after STA–SCA bypass and provide a review of the relevant literature.