Uneven cerebral hemodynamic change as a cause of neurological deterioration in the acute stage after direct revascularization for moyamoya disease: cerebral hyperperfusion and remote ischemia caused by the 'watershed shift'.

Superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis is the standard surgical treatment for moyamoya disease (MMD). The main potential complications of this treatment are cerebral hyperperfusion (CHP) syndrome and ischemia, and their managements are contradictory to each other. We retrospectively investigated the incidence of the simultaneous manifestation of CHP and infarction after surgery for MMD. Of the 162 consecutive direct revascularization surgeries performed for MMD, we encountered two adult cases (1.2%) manifesting the simultaneous occurrence of symptomatic CHP and remote infarction in the acute stage. A 47-year-old man initially presenting with infarction developed CHP syndrome (aphasia) 2 days after left STA-MCA anastomosis, as assessed by quantitative single-photon emission computed tomography (SPECT). Although lowering blood pressure ameliorated his symptoms, he developed cerebral infarction at a remote area in the acute stage. Another 63-year-old man, who initially had progressing stroke, presented with aphasia due to focal CHP in the left temporal lobe associated with acute infarction at the tip of the left frontal lobe 1 day after left STA-MCA anastomosis, when SPECT showed a paradoxical decrease in cerebral blood flow (CBF) in the left frontal lobe despite a marked increase in CBF at the site of anastomosis. Symptoms were ameliorated in both patients with the normalization of CBF, and there were no further cerebrovascular events during the follow-up period. CHP and cerebral infarction may occur simultaneously not only due to blood pressure lowering against CHP, but also to the 'watershed shift' phenomenon, which needs to be elucidated in future studies.