[Effect of head rotation on the vertebrobasilar system. A transcranial Doppler ultrasound contribution to the physiology].

Examination of the vertebrobasilar system until a short time ago was possible only by invasive and therefore potentially harmful techniques. The results of these studies were also contradictory. The objective of the present study was to determine how blood flow velocity differed in the vertebral arteries during head rotation in normal subjects. The origin of cervical vertigo essentially involves three components that are difficult to distinguish. There are the sensory proprioceptive, vascular and sympathicotonic components. Use of transcranial Doppler sonography (TCD) has now made it possible to measure the flow velocity of the vertebral arteries. In 17 normal probands without vertigo or cervical nystagmus, the mean diameters of the vertebral arteries were measured by means of duplex scanning. TCD was used to determine the mean flow velocities of the vertebral arteries in a median position and after head rotations of 30 degrees and 60 degrees to the left and right. Blood flow velocities in both vertebral arteries were not altered by head rotation. This observation contrasted with that of other publications, which were mainly based on cadaver findings. The results of this study form the basis for further investigations on symptomatic patients with recurring cervical nystagmus and cervical vertigo.