Positron emission tomography in the asphyxiated term newborn: parasagittal impairment of cerebral blood flow.

Hypoxic-ischemic encephalopathy secondary to perinatal asphyxia in the term newborn is the most common recognized cause of the subsequent motor deficits often grouped under the rubric "cerebral palsy." In order to provide insight into the basic nature and pathogenesis of the brain injury in such infants, we studied regional cerebral blood flow (CBF) by positron emission tomography (PET) in 17 asphyxiated term infants during the acute period of illness. A consistent and apparently unifying abnormality was observed, namely, a relative decrease in CBF to parasagittal regions, generally symmetrical and more marked posteriorly than anteriorly. Thus, parasagittal values for CBF were generally 25 to 50% lower than those for the sylvian cortex; in the normal or near normal infant, parasagittal values are only approximately 10% lower than those for the sylvian cortex. (Additional normal findings for regional CBF were 50% higher flows to the cerebral cortex than to the cerebral white matter and flows to the basal ganglia and thalamus at least as high as those to the cerebral cortex). That the relative deficit in CBF to parasagittal regions reflects tissue injury was indicated by the close topographic correlation on technetium brain scans in 3 patients of increased tissue uptake of radionuclide and the CBF abnormality. Moreover, the single patient studied at postmortem examination exhibited parasagittal ischemic cerebral injury that correlated well with the PET abnormality of regional CBF. The topography of the PET abnormality, i.e., the cerebrovascular watershed regions, suggests that the brain injury is basically ischemic and that the pathogenesis relates to impaired cerebral perfusion, perhaps secondary to systemic hypotension occurring in association with the perinatal asphyxia. Experimental data support this formulation.