Published Online
on December 29, 2005

A more recent version of this article appeared on February 1, 2006

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Submitted on September 29, 2005
Revised on November 8, 2005
Accepted on November 13, 2005

Cerebral Oxygen Metabolism and Neuronal Integrity in Patients With Impaired Vasoreactivity Attributable to Occlusive Carotid Artery Disease

Satoshi Kuroda MD, PhD^*; Tohru Shiga MD, PhD; Kiyohiro Houkin MD, PhD; Tatsuya Ishikawa MD, PhD; Chietsugu Katoh MD, PhD; Nagara Tamaki MD, PhD; and Yoshinobu Iwasaki MD, PhD

From the Departments of Neurosurgery (S.K., T.I., Y.I.) and Nuclear Medicine (T.S., C.K., N.T.), Hokkaido University Graduate School of Medicine, Japan; and Department of Neurosurgery (K.H.), Sapporo Medical University, Japan.

^* To whom correspondence should be addressed. E-mail: skuroda{at}med.hokudai.ac.jp.

Background and Purpose--It 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.

Methods--This study included 46 patients who had decreased CBF and CVR on N-isopropyl-p-¹²³I-iodoamphetamine SPECT in the ipsilateral middle cerebral artery area attributable to occlusive carotid diseases. Hemodynamic and metabolism parameters were determined in all patients by ¹⁵O-gas PET, and neuronal integrity was evaluated in 19 patients using ¹¹C-flumazenil (FMZ) PET.

Results--OEF 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.

Conclusions--The 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.

Key words: acetazolamide • cerebral ischemia • flumazenil • metabolism • oxygen

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