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The authors describe a method for measuring cerebral tissue respiration by mass spectrometry. The first applications concern the action of vaso-active drugs on intracerebral PCO2 and PO2. The information gained with this method may prove of value in elucidating the mechanisms of drug action and the regulatory mechanisms of cerebral blood flow. Further prospects of experimentation offered by the method are mentioned.

Sixteen patients with subcortical vascular lesions of one hemisphere, (7 left, including 4 aphasics and 9 right, 4 of which had a left neglect syndrome) and 4 controls without noticeable cerebral pathology underwent cerebral blood flow (CBF) measurements with intra-venous Xe 133, both at rest and during activation. The latter consisted of listening to a text together with eye opening and was considered non specific. At rest, a non significant CBF lowering on the side of the lesion was found in most patients, mainly in right brain damaged ones. Hypoperfusion areas (HA) were noted, predominantly in parieto-temporal cortex in right lesions, and in lower and middle frontal areas as well in left lesions. HA persisted during activation on both sides, except on the right side in left damaged patients. Activation resulted in a bilateral and roughly symmetrical mean CBF increase, which was not significant in left lesions nor in controls, but was significant (p less than .05) in right brain damaged patients without neglect syndrome. Conversely, patients with right lesions resulting in left neglect exhibited conspicuous mean CBF asymmetry during activation with depression on the right side. Right-left difference in mean CBF was significantly higher in this group than in right sided lesions without neglect (p less than .05). These facts are consistent with an activation imbalance between hemispheres as the mechanism of unilateral neglect syndromes, and support the view that right subcortical pathways and especially the thalamus, play a part in the activation of both cerebral hemispheres.