Ultrasound diagnostics of the intracranial brain arteries and monitoring techniques

There have been significant further developments in ultrasound diagnostics of the intracranial brain arteries in recent years. Besides the traditional transcranial Doppler sonography (TCD) the two-dimensional colour duplex te chnique (TCCS) has become a well-established method. This enables a safe di fferentiation of the basal brain arteries even without compression tests, a s well as a clear definition against surrounding parenchymal structures. It is now possible to obtain safe and rapid information on the vascular statu s for immediate diagnosis in brain infarction patients. Since information o n vascular malformations and aneurysms can be obtained only if the vascular pathology is sufficiently large, TCCS cannot replace other methods of iden tification as far as this aspect is concerned. The ultrasound contrast medi a for whom the lungs are patent greatly improve the signal-to-noise ratio o f the Doppler signal. After enhancement by the ultrasound contrast media, D oppler signals may be analysed even under unfavourable conditions (for exam ple: insufficient penetration of sound through the temporal bone). By means of haemodynamic TCD monitoring it is now possible to determine significant characteristics of brain blood supply with relatively little effort, such as changes in the median speed of flow, cerebrovascular resistance and auto regulation. The clinical application of this kind of monitoring is demonstr ated by three examples. During the interventional neuroradiological experim ental occlusion of the internal carotid artery the TCD data can be used to assess haemodynamic and possible clinical effects of such an occlusion. In the tilting-table test ICD can supply valuable insights into the cerebral e ffects of systemic dysregulations. In a subgroup of patients with orthostat ic intolerance it was only TCD that showed clear pathological changes. For practical reasons it has not yet been possible to establish TCD monitoring in continuous control checking in stroke units. However, first experiences seem to point out that possibly TCD monitoring may reveal the development f or critical cerebral circulatory disturbances in patients with space-occupy ing media infarctions and may thus supply a significant contribution to the indication for cranial decompression. By means of repeat examinations of t he course, using the TCD and TTCS technique, it is possible to identify in patients with acute cerebral infarction the time of rechannelling and to es timate the space-occupying effect of an infarction by measuring the displac ement of the third ventricle. Monitoring patients after thrombendarterectom y of the internal syndrome, whereas monitoring of an embolism helps to esti mate the risk of a post-operative ischaemic event.