Transcranial Doppler sonography in children.

The blood flow velocities in the basal cerebral arteries can be recorded at any age by transcranial Doppler sonography. By a standardized examination technique, the vessel identification is reliable even without visual control of the site of the sample volume. A stable state of vigilance is necessary to obtain constant recordings. Age has a tremendous influence on the flow velocities. The velocities increase rapidly during the first weeks and reach their maximum around the sixth year of life. The influence of carbon dioxide partial pressure, gestational age, birth weight, hematocrit, and vigilance on the velocities has to be considered. Heart rate and arterial blood pressure are relevant only in cases of extreme values. The clinical applications of transcranial Doppler sonography cover diseases like patent ductus arteriosus, perinatal brain damage, increased intracranial pressure, cerebral malformations, brain death, and stenoses and occlusions of main cerebral arteries. The technique is helpful for control of certain therapies. A continuous recording technique has also been developed for this purpose. Care should be taken in deriving a prognosis from Doppler recordings.