Objective: Superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis is the standard surgical management for adult moyamoya disease (MMD) patients, but local cerebral hyperperfusion (CHP) and cerebral ischemia are potential complications of this procedure. Recent hemodynamic analysis of the acute stage after revascularization surgery for MMD revealed a more complex and unique pathophysiological condition, the so-called “watershed shift (WS) phenomenon,” which is defined as a paradoxical decrease in the cerebral blood flow (CBF) at the adjacent cortex near the site of local CHP. The objective of this study was to clarify the exact incidence, clinical presentation, and risk factors of the WS phenomenon after direct revascularization surgery for adult MMD. Patients and Methods: Among 74 patients with MMD undergoing STA-MCA anastomosis for 78 affected hemispheres, 60 adult patients comprising 64 hemispheres underwent serial quantitative CBF analysis by N-isopropyl-p-[123I] iodoamphetamine single-photon emission computed tomography after revascularization surgery. The local CBF was quantitatively measured at the site of anastomosis and the adjacent cortex before surgery, as well as on 1 and 7 days after surgery. Then, we investigated the incidence, clinical presentation, and risk factors of the WS phenomenon. Results: The WS phenomenon was evident in 7 patients (7/64 hemispheres; 10.9%) after STA-MCA anastomosis for adult MMD. None of the patients developed neurological deterioration due to the WS phenomenon, but 1 patient developed reversible ischemic change on diffusion-weighted imaging at the site of the WS phenomenon. Multivariate analysis revealed that a lower preoperative CBF value was significantly associated with the occurrence of the WS phenomenon (20.3 ± 7.70 mL/100 g/min in WS-positive group vs. 31.7 ± 8.81 mL/100 g/min in WS-negative group, p= 1.1 × 10–2). Conclusions: The incidence of the WS phenomenon was as high as 10.9% after STA-MCA anastomosis for adult MMD. The clinical outcome of the WS phenomenon is generally favorable, but there is a potential risk for perioperative cerebral infarction. Thus, we recommend routine CBF measurement in the acute stage after revascularization surgery for adult MMD to avoid surgical complications, such as local CHP and cerebral ischemia, caused by the WS phenomenon. Concomitant detection of the WS phenomenon with local CHP is clinically important because blood pressure reduction to counteract local CHP may have to be avoided in the presence of the WS phenomenon.

Objective: Superficial temporal artery (STA)-middle cerebral artery (MCA) anastomosis is a standard surgical procedure for adult patients with moyamoya disease (MMD) and plays a role in preventing ischemic and/or hemorrhagic stroke. Cerebral hyperperfusion (CHP) syndrome is a potential complication of this procedure that can result in deleterious outcomes, such as delayed intracerebral hemorrhage, but the exact threshold of the pathological increase in postoperative cerebral blood flow (CBF) is unclear. Thus, we analyzed local CBF in the acute stage after revascularization surgery for adult MMD to predict CHP syndrome under modern perioperative management. Materials and Methods: Fifty-nine consecutive adult MMD patients, aged 17–66 years old (mean 43.1), underwent STA-MCA anastomosis with indirect pial synangiosis for 65 affected hemispheres. All patients were perioperatively managed by strict blood pressure control (systolic pressure of 110–130 mm Hg) to prevent CHP syndrome. Local CBF at the site of anastomosis was quantitatively measured using the autoradiographic method by N-isopropyl-p-[123I] iodoamphetamine single-photon emission computed tomography 1 and 7 days after surgery, in addition to the preoperative CBF value at the corresponding area. We defined CHP phenomenon as a local CBF increase over 150% compared to the preoperative value. Then, we investigated the correlation between local hemodynamic change and the development of CHP syndrome. Results: After 65 surgeries, 5 patients developed CHP syndrome, including 2 patients with delayed intracerebral hemorrhage (3.0%), 1 with symptomatic subarachnoid hemorrhage (1.5%), and 2 with focal neurological deterioration without hemorrhage. The CBF increase ratio was significantly higher in patients with CHP syndrome (270.7%) than in patients without CHP syndrome (135.2%, p = 0.003). Based on receiver operating characteristic analysis, the cutoff value for the pathological postoperative CBF increase ratio was 184.5% for CHP syndrome (sensitivity = 83.3%, specificity =  94.2%, area under the curve [AUC] value  =  0.825) and 241.3% for hemorrhagic CHP syndrome (sensitivity =  75.0%, specificity =  97.2%, AUC value  =  0.742). Conclusion: Quantitative measurement of the local CBF value in the early postoperative period provides essential information to predict CHP syndrome after STA-MCA anastomosis in patients with adult MMD. The pathological threshold of hemorrhagic CHP syndrome was as high as 241.3% by the local CBF increase ratio, but 2 patients (3.0%) developed delayed intracerebral hemorrhage in this series that were managed following the intensive perioperative management protocol. Thus, we recommend routine CBF measurement in the acute stage after direct revascularization surgery for adult MMD and satisfactory blood pressure control to avoid the deleterious effects of CHP.

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A 38-year-old man with severe canal stenosis at the level of the atlas is reported. The clinical manifestations were muscular weakness and wasting of the upper limbs and spastic paresis of the lower limbs, which all progressed slowly. The atlas was hypoplastic and its retrodental space was narrow. The spinal cord was markedly compressed between the odontoid process and the posterior arch of the atlas. The clinical manifestations improved after a posterior laminectomy of the atlas.

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