Transcranial Doppler sonography. Examination technique and normal reference values.

The main application of ultrasound in neurology is the examination of extracranial arteries. Recently the Doppler sonographic measurement of flow velocity in the basal cerebral arteries through the intact skull was developed using a pulsed Doppler technique and 2 MHz emitting frequency. Doppler frequencies in systole and diastole were recorded in 51 healthy subjects at 0.5 cm steps along the middle (MCA), anterior (ACA) and posterior cerebral artery (PCA) as well as the basilar artery (BA). The averaged Doppler shift in the MCA was 2.3 +/- 0.4 kHz in systole and 1.15 +/- 0.25 kHz in diastole, in the ACA 1.8 +/- 0.35 kHz and 0.85 +/- 0.22 kHz, in the PCA 1.5 +/- 0.29 kHz and 0.74 +/- 0.18 kHz, in the BA 1.45 +/- 0.31 kHz and 0.72 +/- 0.22 kHz. Separation in four age groups showed a decrease of Doppler shift in the MCA of 20% from a mean age of 17 to 67 years. Static and dynamic compression tests were evaluated to assign transcranial Doppler signals to the MCA, ACA and PCA. No compression test was necessary for the identification of the BA insonated through the occipital foramen.