Transcranial US and Color Doppler studies in Neonatal Hypoxic-Ischemic Brain Insults

Abstract

HIE is an important cause of morbidity and mortality in the neonatal period and of cerebral palsy as a late neurologic sequel in the postnatal period. Although intervention is limited and mostly supportive at this time, it is still important to promptly and accurately identify neonates who have sustained a hypoxic-ischemic brain injury to facilitate optimal management. Cranial US with its own advantages and disadvantages, show characteristic patterns of brain injury that correlate well with the degree of hypotension and the level of brain maturity at the time of the insult, thus excluding other causes of encephalopathy and limiting the diagnosis to HIE. HII can pose a difficult diagnostic problem from a neuroimaging standpoint, especially in newborns. Observed injury patterns are highly variable and depend on brain maturity, severity and length of insult, and type and timing of imaging. Making the diagnosis of HII at US, CT, and MR imaging requires a clear understanding of the various imaging patterns that can result. By focusing on the specific regions that are most likely to be injured due to selective vulnerability, one can avoid false-negative interpretations caused by overlooking subtle findings in an otherwise normal-appearing brain. Cranial ultrasound is currently in routine use in neonatal intensive care units and was found to be an excellent and non-invasive tool for brain imaging during the neonatal period. It enables screening of the brain and serial imaging in high-risk neonates. In experienced hands, cranial ultrasound is an excellent tool to detect the most frequently occurring brain abnormalities in preterm and full-term neonates, to study the evolution of lesions. Transcranial ultrasonography is the most widely used neuroimaging technique in both premature and full term infants. The high susceptibility to hypoxia of the preterm brain explains the raised prevalence of intracranial haemorrhage at this group of patients. Ultrasound examination contributes to assessment of the neurologic status in children by diagnosing and staging of the intracranial bleeding, and brings information about immediate and long term prognosis. The two major pictures of cerebral damage secondary to perinatal hypoxia are: peri and intraventricular haemorrhage and periventricular leucomalacia respectively. Cerebral artery Doppler ultrasonography is a useful tool for the evaluation of the cerebral hemodynamics in asphyxiated newborns admitted to the neonatal intensive care unit. The degree and duration of cerebral hemodynamic alterations are in direct correlation with the severity of the disease and later outcome. RI and cerebral velocities are predictive for prognosis. Early Doppler investigation may be important in neonatal screening after hypoxic-ischemic injury to delineate the risk group, and, interpreted in respect to clinical data, it may lead the clinicians’ management. Cranial U/S is an excellent screening modality for use in neonates too critically ill to be transported to MRI. Also is very sensitive in detecting injuries and is often the only study available during the initial evaluation of these critically ill patients or in those under hypothermic treatment. US provides an option for the interval follow-up assessment of these infants