• Satoshi Kuroda, Tohru Shiga, Kiyohiro Houkin, Tatsuya Ishikawa, Chietsugu Katoh, Nagara Tamaki, and Yoshinobu Iwasaki.
• Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan. skuroda@med.hokudai.ac.jp
• Stroke. 2006 Feb 1;37(2):393-8.

Background And PurposeIt is still unclear that impaired cerebrovascular reactivity (CVR) to acetazolamide is comparable to elevated oxygen extraction fraction (OEF) on positron emission tomography (PET) in patients with occlusive carotid diseases. Therefore, in this study, the authors aimed to clarify whether OEF is elevated in all patients with reduced cerebral blood flow (CBF) and CVR (type 3) on single photon emission computed tomography (SPECT), and, if not, to specify the underlying pathophysiology of type 3 but normal OEF.MethodsThis study included 46 patients who had decreased CBF and CVR on N-isopropyl-p-(123)I-iodoamphetamine SPECT in the ipsilateral middle cerebral artery area attributable to occlusive carotid diseases. Hemodynamic and metabolism parameters were determined in all patients by (15)O-gas PET, and neuronal integrity was evaluated in 19 patients using 11C-flumazenil (FMZ) PET.ResultsOEF was significantly elevated in 20 (43.5%) of 46 type 3 patients. Another 26 type 3 patients had normal OEF. Regression analysis showed that OEF significantly correlated with cerebral metabolic rate for oxygen and 11C-FMZ binding potential but not with other parameters. Subcortical infarction had no significant effect on OEF values.ConclusionsThe results strongly suggest that type 3 patients with reduced CBF and CVR may be divided into 2 pathophysiologically different subgroups: misery perfusion attributable to hemodynamic compromise and matched hypometabolism attributable to incomplete infarction. Type 3 but normal OEF may represent a transition stage from misery perfusion to matched hypometabolism.

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