[Identification of the basilar artery with transcranial Doppler sonography].

In 100 normal subjects the flow velocity in the terminal segments of the vertebral arteries and the basilar artery was investigated by suboccipital transcranial Doppler sonography. In normal cases, flow velocity and direction are not sufficient criteria to differentiate these arteries. Using anatomical and haemodynamical parameters it can be shown that a Doppler signal originating from the basilar artery cannot be expected in a depth of less than 85 mm, thus being deeper than it is usually reported in the literature. Due to methodological limitations, the basilar artery cannot be insonated in about 30% of cases.