Developmental change of blood flow velocity and pulsatility index (PI) of the basilar artery (BA) were studied, using transcranial Doppler sonography on 137 healthy subjects (68 males and 69 females) from 1 month to 30 years old.
Blood flow velocity of the basilar artery increased with age during infancy and childhood, reached the maximum at the age of 5, and then gradually decreased. It ratio to blood flow velocity of the middle cerebral artery (MCA) i.e. MCA/BA showed a constant value irrespective of age. On the other hand, PI of the basilar artery showed a maximum value at infancy, and decreased during 1-2 years of age thereafter, it showed a constant value. Physiological variation of the blood flow velocity of MCA and BA during natural sleep and hyperventilation was also investigeted. There is a close correlation between the optimal pulsed signal depth for the measurement of blood flow velocity of the basilar artery and head circumference, or occipito-frontal diameter.