Regional cerebral blood flow and verbal memory after chronic exposure to organic solvents

Regional cerebral blood flow (rCBF; 133Xe-inhalation method) was investigated in 32 industrial workers (age: 51 +/- 9 years) who had been exposed to organic solvents during an average of 24.5 years. The measurements were made at rest and during learning of associated word pairs. The resting flow level was 17% lower than expected for normal subjects of similar age and the activation-induced changes of rCBF during the test lacked the frontal activation normally seen. Significant correlations between age, length of exposure, and rCBF level were found. In order to control for the age factor, results were also calculated from two subgroups of similar age but with very different levels of exposure (13 and 31 years of average exposure). The two groups differed only slightly in resting rCBF. A marked difference was, however, seen during activation, with significant post-central flow increases recorded in the lower-exposed group only. The results indicate the potential of the rCBF method for elucidating functional cortical changes related to neurotoxic effects of organic solvents.     

Regional cerebral blood flow measurements by 133Xe-inhalation: Methodology and applications in neuropsychology and psychiatry

This review describes methodological improvements of the ¹³³Xe-inhalation technique for measurement of regional cerebral blood flow (rCBF) comprising correction routines both for scattered radiation from air passages and for remaining activity from previous measurements, as well as a new index of curve fit exactness. Measurements in normals are described showing new characteristics of the resting flow pattern and localized flow changes during activation with a variety of mental tasks. Our clinical applications in psychiatry are reviewed demonstrating the ability of the rCBF technique for differential diagnosis of dementia, for the evaluation of treatment by drugs, ECT, or psychosurgery, as well as for following, cases of toxic influence. The paper finally discusses the potentials as well as the limitations and artifacts of the technique.     

Regional blood flow changes in the left cerebral hemisphere during word pair learning and recall

Regional cerebral blood flow measurements were made in the left hemisphere of 11 young healthy volunteers during learning and during recalling of word pair associates. Compared to the resting baseline, both tasks caused significant increases of average hemispheric flow, indicating an elevated neuronal activity level. Regionally both tasks were accompanied by considerable activation of parietal and occipital regions. The main difference between learning and recalling was that only the former task activated the prefrontal regions.