Rapid Resolution of Brain Ischemic Hypoxia After Cerebral Revascularization in Moyamoya Disease BACKGROUND: In moyamoya disease (MMD), cerebral revascularization is recom- mended in patients with recurrent or progressive ischemic events and associated reduced cerebral perfusion reserve. Low-flow bypass with or without indirect revas- cularization is generally the standard surgical treatment. Intraoperative monitoring of cerebral partial pressure of oxygen (PtiO 2 ) with polarographic Clark-type probes in cerebral artery bypass surgery for MMD-induced chronic cerebral ischemia has not yet been described. OBJECTIVE: To describe basal brain tissue oxygenation in MMD patients before revascularization as well as the immediate changes produced by the surgical procedure using intraoperative PtiO 2 monitoring. METHODS: Between October 2011 and January 2013, all patients with a diagnosis of MMD were intraoperatively monitored. Cerebral oxygenation status was analyzed based on the Ptio 2 /PaO 2 ratio. Reference thresholds of PtiO 2 /PaO 2 had been previously defined as below 0.1 for the lower reference threshold (hypoxia) and above 0.35 for the upper reference threshold (hyperoxia). RESULTS: Before STA-MCA bypass, all patients presented a situation of severe tissue hypoxia confirmed by a PtiO 2 /PaO 2 ratio ,0.1. After bypass, all patients showed a rapid and sustained increase in PtiO 2 , which reached normal values (PtiO 2 /PaO 2 ratio between 0.1 and 0.35). One patient showed an initial PtiO 2 improvement followed by a decrease due to bypass occlusion. After repeat anastomosis, the patient’s PtiO 2 increased again and stabilized. CONCLUSION: Direct anastomosis quickly improves cerebral oxygenation, immediately reducing the risk of ischemic stroke in both pediatric and adult patients. Intraoperative PtiO 2 monitoring is a very reliable tool to verify the effectiveness of this revascularization procedure. KEY WORDS: Brain/diagnosis/metabolism/surgery, Brain/metabolism, Cerebrovascular circulation/physiology, Hypoxia-ischemia, Intraoperative/methods, Monitoring, Oximetry/methods Neurosurgery 76:302–312, 2015 DOI: 10.1227/NEU.0000000000000609 www.neurosurgery-online.com M oyamoya disease (MMD) is a cerebro- vascular disorder characterized by pro- gressive occlusion of both terminal internal carotid arteries with consequent hyper- trophy and proliferation of the lenticulostriate arteries to form a collateral circulation network. 1,2 The term MMD is reserved for cases of unknown etiology. In contrast, moyamoya syn- drome is a similar condition with an underlying cause, such as arteriosclerosis, radiotherapy, Down syndrome, meningitis, and sickle cell disease, and induces a progressive unilateral or bilateral steno-occlusion with the associated compensatory development of a collateral net- work. 3,4 Takeuchi and Shimizu 5 were the first to describe this disease in the Japanese literature in 1957 in a patient with “hypoplasia of the bilateral internal carotid arteries.” The term moyamoya was first introduced in 1969 when Fuat Arikan, MD* Jordi Vilalta, MD, PhD* Ramon Torne, MD* Montserrat Noguer, MD, PhD‡ Carles Lorenzo-Bosquet, MD§ Juan Sahuquillo, MD, PhD* *Department of Neurosurgery and the Neurotraumatology and Neurosurgery Research Unit (UNINN); ‡Departments of Anesthesiology and §Nuclear Medi- cine, Vall d’Hebron University Hospital, Universitat Auto ` noma de Barcelona, Barcelona, Spain Correspondence: Fuat Arikan, MD, Department of Neurosurgery, Vall d’Hebron University Hospital, Paseo Vall d’Hebron 119-129, Barcelona, Spain. E-mail: farikan@vhebron.net Received, August 6, 2014. Accepted, October 20, 2014. Published Online, January 12, 2015. Copyright © 2015 by the Congress of Neurological Surgeons. ABBREVIATIONS: CBF, cerebral blood flow; EMS, encephaloduromyosynangiosis; FiO 2 , fraction of inspired oxygen; MMD, moyamoya disease; PtiO 2 , cerebral partial pressure of oxygen; SBP, systolic arterial blood pressure; SPECT, single-photon emission computed tomography; STA-MCA, Super- ficial temporal artery to middle cerebral artery; Tc-99m, technetium-99m RESEARCH—HUMAN—CLINICAL STUDIES RESEARCH—HUMAN—CLINICAL STUDIES 302 | VOLUME 76 | NUMBER 3 | MARCH 2015 www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited