In three patients with vertebral artery dissection presenting subarachnoid hemorrhage, hemodynamic changes in the affected arteries were investigated by transcranial Doppler sonography (TCD) . On measurement of the vertebrobasilar system by TCD, a combined midline and lateral approach was used for accurate evaluation of the hemodynamic state of the system.
Two-layered Doppler waveform was recorded in two patients, and decrease of the flow velocity in the affected artery compared with the contralateral vertebral artery was recorded in the other patient. This two-layered waveform may be a direct finding of arterial dissection.
