Transcranial Doppler sonography and its application in extracranial-intracranial bypass surgery

Transcranial Doppler sonography is a new non-invasive technique to measure atraumatically intracranial haemodynamics. The Doppler principles and the investigative procedure with respect to the cranio-cerebral topography in normal subjects are described. Normal blood flow velocities in the circle of Willis and the influence of age and CO2-pressure are discussed in Part I. With the Doppler method, a description of the pre- and postoperative intracranial haemodynamics in patients undergoing extracranial-intracranial bypass surgery is possible for the first time. Superficial temporal artery compression tests demonstrate the contribution of the bypass to the brain circulation. Bypass surgery can be controlled without angiography. The surgeon can gain a better understanding of the haemodynamics of circulation in the brain.