Search

Spontaneous dissection of brain-supplying cervical arteries, which also includes findings after minor injuries, is one of the main causes of ischaemic strokes in young adults. Strokes due to dissection are usually due to arterio-arterial embolism. They are rarely the first symptom of dissection because an intraluminal thrombus must first develop. Therefore, early diagnosis of dissection can contribute to stroke prevention - through immediate therapy with anticoagulants or antiplatelet drugs. This article describes the diagnostic criteria and typical findings of spontaneous dissection, in which no dissecting membrane is to be expected as in aortic dissection. Traumatic dissections following blunt or penetrating injuries also present with different findings. Examiners should be aware of possible differential diagnoses whose ultrasound image may mimic a dissection. A frequently occurring but avoidable cause of misdiagnosis is idiopathic carotidynia. Ultrasound also enables differentiation between dissection and vasculitis or carotid web and detection of normal variants such as fenestration of the vertebral artery. Further possibilities for misdiagnosis may arise in the presence of a variant of the ascending pharyngeal artery or in extracranial vasospasm. The different imaging techniques for the detection of a dissection are complementary, as false-negative findings occur with all techniques; no method serves as the gold standard. In any case, ultrasound can make an important contribution to the detection of a dissection, and it is worth knowing the diagnostic criteria., Competing Interests: Declaration of financial interestsReceipt of research funding: no; receipt of payment/financial advantage for providing services as a lecturer: no; paid consultant/internal trainer/salaried employee: no; patent/business interest/shares (author/partner, spouse, children) in company: no; patent/business interest/shares (author/partner, spouse, children) in sponsor of this CME article or in company whose interests are affected by the CME article: no.Declaration of non-financial interestsThe authors declare that there is no conflict of interest., (Thieme. All rights reserved.)

Since 1986, German ultrasound criteria for grading carotid stenosis have followed the local diameter reduction percentage consistent with the definition used in the European Carotid Surgery Trial (ECST) definition. To overcome the confusion caused by the coexisting grading method used in the North American Symptomatic Carotid Endarterectomy Trial (NASCET), a German interdisciplinary council on carotid artery stenosis has recommended the implementation of the NASCET grading system (distal diameter reduction percentage) as the standard. The multi-parametric German "DEGUM ultrasound criteria" consisting of combined Doppler and imaging criteria have consequently been revised and transferred to the NASCET definition. In addition, a novel differentiation between main (primary) and additional (secondary) criteria has been proposed. When these ultrasound criteria are combined, vascular sonography allows reliable grading of carotid disease., (Copyright Georg Thieme Verlag KG Stuttgart . New York.)

Aim: To evaluate the usefulness of various sonographic criteria for detecting a dissection of the internal carotid artery (ICA)., Method: Twenty-three consecutive patients displaying typical clinical symptoms of ICA dissection were identified. The diagnosis of dissection in these cases was confirmed by MRI/MRA or arteriography. The sonographic examination was the first technical investigation and involved the combined use of Doppler and duplex sonography. The value of different sonographic criteria was evaluated for the identification of ICA dissection: 1) Morphological criteria: intramural haematoma or double lumen. 2) Haemodynamic findings of distal stenosis/occlusion in combination with suddenly appearing clinical signs of a space-occupying lesion in the respective region (Horner's syndrome, lower cranial nerve palsies). 3) Haemodynamic signs of distal stenosis/occlusion with ensuing recanalisation within a few weeks., Results: Morphological criteria alone allowed detection of a dissection in 47,8 % of patients. By the combined use of morphological and haemodynamic criteria ICA dissections were identified on admission in 73.9 % and after an average of 4.5 weeks (at the latest after 6 weeks) in 91.3 % of the patients., Conclusion: ICA dissections can be identified sonographically with high sensitivity. In some of the cases, however, definite diagnosis can only be provided by follow-up evaluation.

Unlabelled: Therapeutic decisions in cases of arteriosclerotic stenosis of the internal carotid artery usually depend mainly on the degree of stenosis. However, the recommendations with regard to suitable ultrasonographic criteria are so controversial that even authors of repute describe "confusion" and "chaos in methodology"., Aim: The aim of this study is to assess which of the most frequently recommended sonographic criteria for stenosis best fulfill the requirements of an exact quantification of stenoses of the internal carotid artery., Method: In 42 consecutive cases the preoperative ultrasound findings were compared with the degree of stenosis in surgically removed specimens. The sonographic technique employed consisted of the analysis of 2 direct and 3 indirect hemodynamic criteria of stenosis. In 34 of these cases planimetry was performed, too. The specimens were obtained by eversion thrombendarteriectomy or arteriotomy; for determination of the degree of stenosis a Paladur molded cylinder was prepared and measured., Results: Quantification of the haemodynamic criteria carries provided well with the endarterectomy specimens. Only in two cases there was a deviation of more than 10 %; however, in these two cases a change with time in the degree of stenosis was probably responsible for the discrepancy. In contrast, planimetry usually underestimated the degree of stenosis: In 61 % of the findings the ultrasonographic results differed by more than 10 % from the reference standard., Conclusion: Quantification of stenosis of the internal carotid artery should be made using a combination of direct and indirect haemodynamic ultrasonographic criteria.

Unlabelled: Perivascular tissue vibrations, an artefact of the colour Doppler method, are already known to be a sonographic sign of stenosis but have not yet been investigated systematically in the examination of the internal carotid artery., Aim: The present study is intended to assess the value of this artefact in the diagnosis of stenosis of the internal carotid artery., Method: A total of 167 consecutive cases including a stenosis of the internal carotid artery of at least 50% were diagnosed according to the usual haemodynamic criteria using Doppler and duplex sonography and classified into 10% categories. Intermediate groups were formed for findings that could not be assigned unambiguously. By means of suitable apparatus settings each finding was examined to test whether a perivascular colour artefact was detectable., Results: In the stenosis categories of 50% to 70% no perivascular colour artefact was found, whereas in the stenosis categories of 80% to 90% this was the case in 80% of the findings, and in the intermediate 75% category in 42% of the findings. The perivascular colour artefact was recognizable even under poor sonographic conditions., Conclusion: When a perivascular colour artefact is seen the diagnosis of a high-degree stenosis (or an AV fistula) is certain. The phenomenon is particularly valuable as a supplementary criterion of stenosis in cases of unfavourable sonographic conditions. However, the perivascular colour artefact may only be used to confirm, but never to exclude, a high-degree stenosis.

The practical application of colour-coded duplex sonography shows that physico-technical artifacts of colour Doppler imaging may not be obvious in all cases and can lead to misinterpretation. Slice-thickness artifacts are due to restricted transversal resolution, as in the B-mode, and may cause false negative results in vascular occlusions. Specific problems in creating and processing the colour flow image interfere with lateral resolution and lead to errors in the quantification of stenoses from the colour Doppler image. Mirror image artifacts produce phantom pictures that can be easily identified as such in some cases, but may resemble recesses in the arterial wall in other cases. Phenomena of sound shadowing resulting from the same reasons as in B-mode may lead to assume vascular occlusions in cases of long-range stenoses. Artifacts of the sonication angle in case of blood vessel tortuosity may lead to misdiagnosis of a non-existent retrograde flow. The artifacts mentioned do restrict the capacity of colour coded duplex sonography for localising flow in the ultrasound image. Users of the method should therefore be familiar with these artifacts.