Transcranial Dopplersonography of the vertebro-basilar system.

This is the first investigation of distances, angles and locations of the vascular system in the posterior fossa. The distances from the skin surface of the neck, where a Doppler probe is positioned for transforaminal insonation, to the brainsystem have been measured in sagittal MRI pictures. The mean distance from the insonation point to the beginning of the basilar artery (BA) is 66.6 mm in males, 58.8 in females. The distance to the end of the BA is 90.0 and 80.4, respectively. These distances are relevant for locating the vertebral and basilar arteries. The insonation angles to the VA and BA range from 20 degrees to 30 degrees. Correlations with Doppler findings are discussed.