Delayed Transcranial Echo-Contrast Bolus Arrival in Unilateral Internal Carotid Artery Stenosis and Occlusion

Some patients with internal carotid artery (ICA) occlusion or stenosis are at risk of developing a hemodynamic stroke. Transcranial ultrasonography using an echo-contrast bolus technique might be able to assess the extent of hemodynamic compromise. We describe a transcranial Doppler sonographic method that analyzes the differences in echo-contrast bolus arrival between both middle cerebral arteries after intravenous echo-contrast application. Ten patients with 50%-79% ICA stenosis, 10 patients with 80%-99% ICA stenosis and 22 patients with ICA occlusion were studied and compared with 15 age-matched controls. There were significant increases in delayed filling of the middle cerebral artery in both 80%-99% stenoses and occlusions compared with controls. The extent of the observed delays did not correlate with vasomotor reactivity. Echo-contrast bolus arrival time can be used to gain additional information on the intracranial hemodynamic effects of extracranial carotid artery disease that seems to be independent of the established ultrasound indices.

Dopplersonographic measurement of global cerebral circulation time using echo contrast-enhanced ultrasound in normal individuals and patients with arteriovenous malformations

Echo-contrast "bolus tracking" by ultrasound (US) is an exciting new tool to study cerebral haemodynamics. In the present study, a global cerebral circulation time (CCT) was measured by extracranial Doppler as the time difference of contrast bolus arrival between the internal carotid artery and internal jugular vein. A total of 64 healthy volunteers and 9 patients with an angiographically diagnosed arteriovenous malformation (AVM) were studied. CCT in volunteers and patients was calculated as the time interval between the points of 10% rise (CCT(1)) and 90% rise (CCT(3)) of the total intensity increase and between the turning points (CCT(2)) of the resulting time-intensity curves. In the volunteer group, CCT(1) was 5.4 +/- 1.8 s, CCT(2) was 7 +/- 1.3 s and CCT(3) 7.5 +/- 1.8 s. CCT results in the AVM group were 2.8 +/- 2.5 s, 3.0 +/- 1.3 s and 4.5 +/- 2.1 s, respectively, and differed significantly from the controls. For the first time, we could confirm a significant shortening of CCT in patients with cerebral AVM by US. The presented test might become a new, additional tool for AVM evaluation and follow-up of treatment in these patients.

Relationship between regional pertechnetate cerebral circulation time and EEG in patients with cerebral infarction

The qualitative and regional correlations between the EEG and the cerebral circulation time (CCT), obtained by using intravenously injected pertechnetate and a multidetector device, were studied in 75 patients with supratentorial cerebral infarction. Because bolus dispersion and changes in systemic circulation may distort absolute CCT values when intravenous injection of the isotope is used, the inter- and intrahemispheric relative CCT values were used as indices of CCT. Overall good correlations could be demonstrated between both inter- and intrahemispheric CCT abnormalities and the EEG, though not in all patients. The number of patients with pathological CCT findings showed a tendency to increase with increasing severity of the EEG abnormality. The number of abnormal CCT areas per patient (indicating the size of the circulation disturbance) also increased significantly with increasing severity of the EEG disturbance. Interestingly, relative 'hypervelocity' areas occurred in fewer patients with normal or clearly disturbed EEGs than in patients with mildly disturbed EEGs, perhaps due to differences in autoregulatory capacity and collateral circulation. Within the EEG focus the relative number of CCT abnormalities was greater than outside it. In spite of this fairly good overall correlation between the EEG focus and the CCT abnormality, more than 10% of the patients with an EEG focus showed no CCT abnormalities, thus indicating the complementary roles of these methods. The present study on cerebral infarction, though using intravenously injected pertechnetate for the CCT measurement, showed a reasonable correspondence with earlier reports on the relationship between the EEG and either the CBF or the CCT (obtained by intra-arterially injected isotope). This would seem to suggest that the used non-invasive method for regional CCT measurement has potential for evaluation of cerebral haemodynamics.