Vergleich der Doppler-/Duplexsonographie und MR-Angiographie in der Diagnostik von Stenosen der A. carotis interna (ACI)

This study compared the additional information derived from the non-invasive and minimally invasive diagnostic methods of Doppler/duplex sonography and MR angiography, which are routinely used in the diagnosis of cerebral ischaemia. 'Additional information' was defined as lesions in the arteries supplying the brain with the exception of ipsilateral symptomatic ICA. The study also investigated and compared the two methods' effectiveness regarding the detection of tandem stenoses of the ipsilateral ICA. The third objective of this study was to investigate the two diagnostic methods' concordance regarding ICA stenosis grading. To do so, the study specifically compared two non-invasive and minimally invasive diagnostic methods to one another without recourse to DSA, which is still regarded as the “golden standard”, as a reference method. This comparison explicitly avoided the use of DSA, which is commonly and widely used in the investigation of similar issues, because of its side effect profile and significant cost. This comparison also expressly focussed on differentiating between ipsilateral and contralateral ICAs in its analyses. Within the framework of the three research questions outlined above, the study also investigated the demographic structure of the patient cohort and the distribution of cardiovascular risk factors, and calculated the average PSVs for the ICA stenosis groups as specified under the NASCET criteria for both the ipsilateral and contralateral vessels. The study revealed that MR angiography is significantly superior to Doppler/duplex sonography regarding the provision of additional information (68.3% vs. 8.3%, p<0.001). Most of the additional information obtained through MRA in this study was from the vertebrobasilar (38.6%) and intracranial vessels (35.7%), which are often described in the literature as areas in which Doppler/duplex sonography performs poorly. However, Doppler/duplex sonography outperformed MRA in the provision of additional information regarding extracranial anterior circulation (55.6% vs. 20% from MRA). In keeping with the few literature sources available on this subject, the findings regarding the methods' effectiveness in detecting ipsilateral tandem stenoses were totally discordant (κ=-0.029, p=0.737). None of the two diagnostic methods was significantly better than the other. However, MRA identified six-times as many ipsilateral tandem stenoses than Doppler/duplex sonography. The analysis of the common cardiovascular risk factors revealed that a disproportionately high number of patients in the patient group with the ipsilateral tandem stenoses had a history of cerebral ischaemia (51.7% vs. 26.4% of the patient group without tandem stenoses) and of regular nicotine/alcohol use (28.6% vs. 15.1% and 9.4% respectively in the patient group without tandem stenoses, however, neither of which are significant). Even though these data are plausible, more patients are required to confirm this trend. The investigation of the correlation between the two diagnostic methods' grading of ICA stenoses showed that there was a high level of discord between the two (26.7% for the ipsilateral and 21.7% for the contralateral side), which is in line with the levels cited in the literature. Both diagnostic methods produced concordant findings, with regard to which it is remarkable that this concordance was far more pronounced on the asymptomatic side (r=0.874) than on the symptomatic side (r=0.616). This phenomenon is described as very rare in the literature and thought to be due to changes in the haemodynamic flow characteristics and the limits of diagnostic imaging regarding vessels that have undergone severe pathological changes on the side that has turned symptomatic. This finding implies that the reliability of pre-operative diagnostic examinations can be increased by combining the two diagnostic methods. The above leads to the following conclusions: MRA provides significantly more additional information than Doppler/duplex sonography. When grading ICA stenosis, it is vital to differentiate between the ipsi- and the contralateral arteries. Despite their many advantages, the results obtained with these non-invasive and minimally invasive diagnostic methods should always be treated with caution and, if the findings are discordant but important to treatment, should be supplemented with a standardised reference method. The two diagnostic methods should therefore be internally validated against a reference method - where necessary, taking into account surgical specimens.