Delayed intrahemispheric remote hypometabolism - Correlations with early recovery after stroke

Although 'intrahemispheric diaschisis' (i.e. a hypometabolism affecting the cerebral hemisphere ipsilateral to but remote from the infarct) may classi cally exacerbate acute-stage neurological deficit and influence early recov ery, it has been studied only rarely. Out of a series of 30 patients with f irst-ever middle cerebral artery (MCA) territory stroke, we analyzed the da ta from 19 survivors investigated by O-15 positron emission tomography (PET ) both in the acute (within 5-18 h of clinical onset) and subacute (approxi mately 3 weeks later) stage, and for whom chronic-stage CT coregistered wit h PET was available to assess infarct topography and size. Orgogozo's MCA s cale was used to assess neurological deficits at the time of, and recovery between, the PET studies. Oxygen consumption was obtained for both PET sess ions for the whole ipsilateral hemisphere (excluding ventricles and infarct ), as well as for the thalamus and the occipital and mesial-prefrontal cort ex (i.e. potentially deafferented tissue outside the MCA territory). In all regions except the occipital cortex, the oxygen consumption significantly decreased between the first and the second session, without significant cor relation with the concomitant changes in MCA scores. However, acute-stage m esial-prefrontal metabolism was significantly correlated with neurological recovery. Also, both the hemisphere and the mesial-prefrontal metabolism at the second session were significantly correlated with both infarct size an d concomitant MCA scores, but the latter relationship became insignificant when infarct size was taken into account. This study reveals no evidence of acute intrahemispheric diaschisis after MCA territory stroke in man. Howev er, it documents for the first time a phenomenon of delayed intrahemispheri c remote hypometabolism developing while the patients clinically recover. B ecause the degree of this secondary phenomenon is a function of infarct siz e, a mechanism of degeneration of the damaged neuron terminals is likely. F inally, contrary to other reports, neurological recovery was not a function of thalamic hypometabolism, but appeared to be influenced by acute-stage m esial-frontal metabolism, perhaps because this region is part of a network that has an important compensatory role in motor recovery. Copyright (C) 20 00 S. Karger AG, Basel.