Developmental and physiologic changes in cerebral blood flow velocity.

Developmental change of mean blood flow velocity (MBFV) and resistance index of the basilar artery (BA), as well as the changes in MBFV of the BA and the middle cerebral artery (MCA) during sleep and hyperventilation, were studied using transcranial Doppler sonography in healthy Japanese subjects. The MBFV of the BA increased with age from infancy through early childhood, reaching the maximum (64.4 +/- 2.6 cm/s) at the age of 5 y, and then gradually decreased. MBFV ratio of MCA to BA was almost stable between 1.57 to 1.64 in all age groups. The resistance index of the BA showed a maximum value in infants, decreased in 1- to 2-y-olds, and remained constant thereafter. The MBFV of both the MCA and BA were lower during non-rapid eye movement sleep than during wakefulness, whereas during rapid eye movement sleep they showed almost the same value as during wakefulness. They were also decreased during hyperventilation. At an expiratory CO2 level of 25 mm Hg (33.33 kPa), the average decrease in MBFV in children (n = 10) was -50.1 +/- 3.9% in the BA, and -46.2 +/- 7.4% in the MCA, significantly (p < 0.05) more marked than that in adults (n = 10) (-41.5 +/- 5.9% and -37.9 +/- 4.2%, respectively). Transcranial Doppler sonography is a noninvasive method that has a potentially wide range of applications in pediatric neurology.