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SUMMARY Tomogrephic images of cerebral blood flow (CBF) and oxygen extraction fraction (OEF) using the U O continuous inhalation technique, and positron emission tomography, were obtained from a patient with cerebral ischemia distal to an occluded left internal carotid artery. There was a focal mismatch between CBF and oxygen metabolism in the brain supplied by tbe middle cerebral artery where CBF was decreased and OEF increased ("misery-perfusion syndrome" as opposed to "luxury-perfusioa syndrome"). These abnormalities were most marked in tbe parieto-ocdpital watershed area. After left superficial temporal to middle cerebral artery anastomosis, the clinical attacks ceased and a repeat study did not demonstrate tbe prerious CBF and OEF abnormalities. This suggests that this pattern of abnormalities indicates potential liable tissue. The concept of "mlsery-perfuslon" may be of some importance In tbe patbophysiological mechanisms of hemodynamic cerebral ischemia and serve as a rational basis for rerascularization procedures.

SUMMARY The oxygen-15 continuous inhalation technique and PET were used to study the age-related changes in regional CBF and CMRO 2 . Twenty-seven patients, aged 19 to 76 years, free of any history of cerebral disease and vascular risk factors were examined in "resting state." CBF, CMRO 2 and oxygen extraction fraction (OEF) values were calculated in seven different brain structures as well as in mean gray matter. Left-right ratios were also computed for all symmetrical structures analyzed.Mean gray CBF, but not mean gray CMRO 2 , decreased linearly with age (p < 0.02). However, when younger subjects (S50 yrs) were compared to older subjects (>50 yrs), an age-related matched decrease in CBF and CMRO 2 was observed in mean gray matter (18% and 17%, p < 0.05) and in all gray matter regions analyzed, particularly in frontal, temporo-sylvian and parieto-occipital cortex. White matter CBF and CMRO 2 remained remarkably stable with advancing age.Although the possibility'of methodological artifacts was considered, we favor progressive loss of cortical neurones and/or diminished activity of those remaining to explain our findings. In addition, age-related changes in cognitive activities might also be involved. Stroke Vol 15, No 4, 1984 DESPITE NUMEROUS STUDIES, 114 the effects of aging on cerebral circulation and metabolism still remain largely unsettled. Studies on global hemispheric cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO 2 ) have so far provided discrepant results: some^ concluded that CBF and CMRO 2 did not decrease with advancing age except when vascular risk factors were present, while other authors 1 2 found a parallel decline in both CBF and CMRO 2 . These discrepancies may be partially explained by different criteria for normality used. In his review on this subject, Kety 7 favored the idea that there was a rapid fall of both CBF and CMRO 2 around puberty which continued to the third decade and was followed by a more gradual decline in middle and old age.

Summary: With the use of positron emission tomog raphy (PET) and the 150 steady-state- [ISF]fluorode oxyglucose combined method, the local interrelationships between the cerebral metabolic rate for oxygen (CMR02) and the cerebral metabolic rate for glucose (CMRGlc) were investigated in control subjects and in stroke pa tients. In addition to the classic in vivo autoradiographic approach, a kinetic method was used to measure CMRGlc because it was expected to be more reliable in cerebral ischemia. In control subjects local coupling be tween CBF, CMR02, and CMRGlc was confirmed, and acceptable values for the CMR02/CMRGlc ratio were found; the latter, however, was lower in white matterThe recent development of independent methods for measuring in the human brain the rates of ox ygen consumption (CMR0 2 ) and glucose utilization (CMRGlc) using positron emission tomography (PET) has revived the study of the coupling be tween CMR0 2 and CMRGlc, previously restricted to the whole brain only (Finkle stein et aI., 1981; Baron et aI., 1982; Rhodes et aI., 1982). Such in vivo studies may help us understand better the con ditions required for the occurrence and the prog nostic significance of enhanced anaerobic glycol ysis in cerebral ischemia.Address correspondence and reprint requests to Dr. Baron at Service Hospitalier Frederic Joliot, CEA Departement de Biol ogie, 91406 Orsay, France.Abbreviations used: CBV, Cerebral blood volume; CMRGlc, cerebral metabolic rate for glucose; CMR02, cerebral metabolic rate for oxygen; CT, computerized tomography; GlcAV, arterio venous glucose difference; ICA, internal carotid artery; MR, metabolic ratio; OEF, oxygen extraction fraction; OM, orbito meatal; PET, positron emission tomography.140 than in gray. Uncoupling between CMR02 and CMRGlc was observed in all stroke patients, suggesting that (1) enhanced anaerobic glycolysis occurred both in reper fused recent infarcts and in chronically ischemic tissue, and (2) substrates other than blood-borne glucose were being oxidized at the borders of recent infarcts. However, methodological uncertainties presently make such obser vations only tentative. Finally, a coupled depression of CMRO, and CMRGlc was found in the contralateral cer ebellu m . Key Words: Cerebral glucose utilization-Ce rebral oxygen consumption-Oxygen-IS -Positron emission tomography. METHODS AND PATIENTS MethodsThe steady-state oxygen-IS method of measuring CBF and CMR02 (Jones et aI., 1976) was combined with the [ISF]fluorodeoxyglucose eSFDG) technique for measuring CMRGlc (Phelps et aI., 1979; Reivich et aI., 1979). A detailed account of the combined measurement has been given earlier (Baron et aI., 1982). Briefly, consecutive continuous inhalation of trace amounts of CI502 and 1502 was performed first. Once completed, 16 min (eight pe riods) were allowed to elapse before rapid (=20 s) intra venous injection of IsFDG (3-8 mCi). Generally, three contiguous head levels, parallel to the orbitomeatal (OM) line, were studied. The coincidence photons were col lected by an EC...

Background and Purpose: Recent reports have shown an increase in specific binding (in vitro) of [3H]PK 11195 to peripheral-type benzodiazepine receptors in both experimental animals and humans, reflecting a glial/macrophagic reaction within and around focal ischemic insults. We have evaluated by positron emission tomography the time course of changes in brain uptake in vivo of "C-labeled PK 11195 and flumazenil (an antagonist of central benzodiazepine receptors) as indirect and direct markers of neuronal loss, respectively, after focal cerebral ischemia.Methods: Ten anesthetized baboons were submitted to sequential positron emission tomography studies between day 1 and day 91 after unilateral middle cerebral artery occlusion. The studies consisted of