Cerebral vasoreactivity and blood flow before and 3 months after carotid endarterectomy.

We measured regional cerebral blood flow and cerebral vasoreactivity before and 3 months after carotid endarterectomy using xenon-133 inhalation with single-photon emission computed tomography and the acetazolamide test in 14 selected patients who had suffered cerebral transient ischemic attacks due to an ipsilateral internal carotid artery stenosis. The patients had neither clinical nor cerebral computed tomographic evidence of infarction. Baseline regional cerebral blood flow was symmetrical before and unchanged after endarterectomy. Before endarterectomy, vasoreactivity in the middle and anterior cerebral artery territories of the symptomatic side was significantly reduced (p less than 0.05); however, vasoreactivity was normalized 3 months after surgery. Our findings strongly suggest that the stenoses caused a reduction in perfusion reserve that was improved by carotid endarterectomy.

Reduced cerebral blood flow in high altitude climbers.

Cerebral blood flow (CBF) was studied by 133Xe inhalation dynamic single photon emission computer tomography in 8 members of a climbing expedition to the Himalayas. With one exception they had all previously climbed at high altitudes. All stayed above 6,500 m for approximately 3 weeks, and 5 reached the summit of Mt. Everest. CBF was measured in Oslo before, immediately after, and one year after the completion of the expedition. Measurements were made at rest and following the injection of 1 g acetazolamide intravenously. As reference group was used 13 healthy male subjects of similar age from the hospital staff. Ten age-matched male diving instructors formed a second control group. In the climbers a small, but not significant reduction in CBF was seen after the expedition. On the other hand, they had significantly lower CBF than reference subjects already before the expedition. The flow difference was most pronounced corresponding to the perfusion territory of the middle cerebral artery. One year after the completion of the expedition the average CBF in climbers was still more than 15% lower than in the reference group. The climbers had higher relative flow increase after acetazolamide injection than the reference subjects, showing that the functional capacity of the microvascular system of the brain was intact. Whether neuronal activity or number of neurones is reduced in climbers proportional to the decrease in flow, or maintained at normal level by increased oxygen and glucose extraction, cannot be answered by the present data.

Measurement of cerebral blood flow with 133Xe inhalation and dynamic single photon emission computer tomography. Normal values.

Cerebral blood flow (CBF) was studied by 133Xe inhalation tomography in 25 healthy subjects. Mean age was 41 years and range 23-66 years. Mean hemispheric CBF at rest was 59.8 ml/100 g/min, and cerebellar flow 60.8 ml/100 g/min. This difference was not statistically significant. The distribution of CBF values was skewed and approximated a log normal distribution. Estimated lower and upper normal reference range limits calculated as mean (log) +/- 2 S.D. (log) were 47-74 ml/100 g/min. Women had approximately 5 ml/100 g/min higher CBF values than men. This difference corresponded to the difference in hematocrit. Neither in men nor in women was there any tendency to age dependent reduction or increase in flow. In both sexes hemispheric regional CBF (rCBF) was asymmetric with higher flow values in the right cerebral hemisphere; particularly in the anterior distribution territory of the middle cerebral artery. In this region the maximum individual flow difference was 8 ml/100 g/min and the average difference 3.5 +/- 2.6 ml/100 g/min. Emotional activation as a consequence of the study conditions is assumed to be the cause of this observed asymmetry. Cerebellar flow was not assymetric. No significant difference in cerebellar or hemispheric CBF was found when a second study followed the first by 3-15 months. PCO2 correction of flow improved the reproducibility. The standard deviation of the flow difference between test/retest measurements was 5 ml/100 g/min. After 1 g acetazolamide given intravenously the mean increase in hemispheric CBF was 15.7 +/- 5.1 ml/100 g/min.(ABSTRACT TRUNCATED AT 250 WORDS)