In 1981, the Norwegian physiologist and cyberneticist, Rune Aaslid, developed a device which made it possible to apply the transcranial Doppler sonographic technique in man. In 1983, Dr. Albrecht Harders took on the project of working out a clinically practicable method that would allow atraumatic measurements to be made of the blood flow velocity in the large branches ofthe circle of Willis. The technique has now become a competitor of the conventional methods of measuring the intracranial hemodynamics, including angiography and the xenon method of cerebral blood flow measurement. Harders proceeded from the assumption that the measurement of the blood flow velocity is more relevant for clinical diagnoses than the usual volume flow measurements. He stresses the very valuable application of the technique in detecting cerebral vasospasm before and after aneurysm surgery.
The changes in the blood flow velocities measured by transcranial Doppler sonography in the individual vessel segments of the circle of Willis are interpreted with respect to the various factors that can effect such changes (collateral circulation in the circle of Willis, diameter of the vessel, vascular resistance, the general cardiovascular situation, arterial partial CO pressure, autoregulatory factors, position of body). The rate of 2 complications associated with angiography has thus been reduced, since the best time both for angiography and for surgery can be determined, and continuous TCD examinations show when the patient is out of a critical phase of cerebral vasospasm.
Hemodynamic Principles.- Physiological Blood Flow.- Principles of Ultrasound Doppler Sonography.- Doppler Formula.- Continuous Wave and Pulsed Doppler Instruments.- Insonation Angle.- Frequency Spectrum Analysis.- Vascular Resistance.- Ultrasound Doppler Sonography and Blood Flow Velocity.- Transcranial Doppler Device.- Ultrasound and the Skull.- Technical Data.- Transcranial Doppler Investigation Technique.- Anatomic Considerations.- Insonation Angle, Measured Depths, and Flow Direction.- Compression Tests.- Normal Values.- Blood Flow Velocity Changes Under Physiological Deviations.- Age.- Blood Flow Velocity End-tidal CO2 Partial Pressure.- Orthostasis and TCD.- Body Acceleration.- Valsalva Test and TCD.- Spontaneous Subarachnoid Hemorrhage and Disturbed Intracranial Hemodynamics.- Hemodynamic Considerations in Stenosis and Vasospasm.- Pathomorphology of the Cerebral Arteries After SAH and Vasospasm.- Timing of Aneurysm Operation.- Natural Time Course of Vasospasm.- Patients.- Method.- Results.- Vasospasm and Aneurysm Surgery Within 72 Hours After Subarachnoid Hemorrhage.- Patients.- Vasospasm Within 72 Hours After the Last SAH.- Vasospasm Between Day 4 and Day 31 After SAH.- Clinical Outcome.- Discussion.- Correlation of Angiographically Confirmed Vasospasm and Stenosis with Transcranial Doppler.- Vasospasm and Delayed Aneurysm Surgery.- Intra-aneurysmal Flow Pattern.- Special Case: Vein of Galen-AVM.- Extracranial-Intracranial Bypass.- Method.- Patients.- Results.- Results: STA Compression Tests and TCD.- Results: Special Cases.- Results: Comparison of CBF Measurements with Transcranial Doppler Sonography.- Discussion.- Arteriovenous Malformations.- Feeding Arteries and Steal Effect.- SAH and AVM.- Vascular Resistance Following Surgical Exclusion.- Superselective Embolization and TCD Recordings.- Discussion.- Monitoring of Frequency Spectra in the MCA During Angiography.- Vascular Hemodynamic Response to Meningitis.- Case Reports.- Discussion.- Brain Death and TCD Recordings.- References.
Number Of Pages: 136
Published: October 1986
Publisher: SPRINGER VERLAG GMBH
Country of Publication: AT
Dimensions (cm): 24.41 x 16.99
Weight (kg): 0.25