The clinical applications of Doppler sonography are numerous in pediatric practice. Of the all the measurements of arterial signals available, the one that has been most useful used and has proved to be of practical benefit is the Pourcelot resistance index (PI). The change in PI is more sensitive than the real-time image for documentation of the cerebral insult in full-term asphyxia. The PI is much lower and stays lower for several days in the more severely asphyxiated infants and is thus extremely useful for predicting outcome as well. But multiple factors affect the waveform and PI, and it is important to understand how physiological and pathological variables influence chances in the Doppler signal in order to better understand changes in newborn with neurological problems. We present the changes of cerebral blood flow by Doppler ultrasound in a newborn with severe perinatal asphyxia and hypoxic-ischemic encephalopathy, associated with other neurological problems; coma, seizures and hydrocephalus.