What is the aim of this review?
The aim of this review was to find out how accurate two imaging techniques - transcranial colour Doppler (TCD) and transcranial colour-coded duplex (TCCD) - are for detecting a blockage of the arteries in the brain in the first hours after a stroke and whether they can be used to select patients who may need to receive more invasive and expensive imaging methods such as intra-arterial angiography (IA), computed tomography angiography (CTA), and magnetic resonance angiography (MRA). There is currently no agreement on the use of TCD and TCCD in the management of people with acute stroke, and the use of TCD and TCCD varies between and within countries.
TCD and TCCD may provide clinically helpful information for detecting a blockage of arteries in the brain when compared with IA, CTA, and MRA.
What was studied in the review?
Ischaemic stroke is the third leading cause of death and the most common cause of long-term disability. It is usually caused by a blockage of the blood supply to one part of the brain. When stroke is caused by a blockage of a large artery due to a blood clot, the prognosis, without treatment, is often poor and can lead to severe disability. Curently, there are two effective treatment options that can be used to dissolve the blood clot: to administer a thrombolytic drug, or to physically extract the blood clot from the artery (mechanical thrombectomy). Both treatments work best within the first few hours of stroke onset. Ultrasound scans (TCD and TCCD) are a quick and simple way to detect the blockage of blood vessels in the brain. We reviewed the current literature for clinical studies assessing the accuracy of these diagnostic techniques compared with IA, CTA, and MRA for the detection of blocked blood vessels in the brain in people with symptoms of ischaemic stroke.
What are the main results of the review
A comprehensive search of major relevant electronic databases from 1982 to 13 March 2018 identified 13,534 articles but only nine studies met the prespecified inclusion criteria. The nine identified studies included a total of 493 stroke patients with similar proportions of men and women. The average age of included participants was 64.2 years (range 55.8 to 69.9 years). Six studies recruited participants in Europe, one in South America, one in China, and one in Egypt. The results of this review indicate that if TCD or TCCD were to be used in a group of 1000 people with symptoms of acute stroke, which in 420 (42%) of them is caused by a blockage of large arteries in the brain, then 428 would have a positive test result but 29 of these (29/428, 7%) would be wrongly identified as positives even though they would not have a blockage of large arteries. Similarly, an estimated 572 would have a negative test result indicating that their symptoms are not caused by a blockage of large arteries in the brain but 21 (21/572, 4%) of these negative cases would actually have a blockage of the large arteries, which TCD or TCCD have missed. In brief, for people with acute ischaemic stroke, TCD or TCCD can provide clinically helpful information for detecting blockage of large arteries in the brain compared with IA, CTA and MRA. Both tests studied in the review (TCD and TCCD) have shown similar accuracy.
How reliable are the results of the studies in the review?
The main limitation of this review is the small number of people assessed by TCD and TCCD in the individual studies. Not enough people have been studied to be really confident about these results. Further larger studies are needed to confirm or refute these results.
This review provides evidence that TCD or TCCD, administered by professionals with adequate experience and skills, can provide useful diagnostic information for detecting stenosis or occlusion of intracranial vessels in people with acute ischaemic stroke, or guide the request for more invasive vascular neuroimaging, especially where CT or MR-based vascular imaging are not immediately available. More studies are needed to confirm or refute the results of this review in a larger sample of stroke patients, to verify the role of contrast medium and to evaluate the clinical advantage of the use of ultrasound.
An occlusion or stenosis of intracranial large arteries can be detected in the acute phase of ischaemic stroke in about 42% of patients. The approved therapies for acute ischaemic stroke are thrombolysis with intravenous recombinant tissue plasminogen activator (rt-PA), and mechanical thrombectomy; both aim to recanalise an occluded intracranial artery. The reference standard for the diagnosis of intracranial stenosis and occlusion is intra-arterial angiography (IA) and, recently, computed tomography angiography (CTA) and magnetic resonance angiography (MRA), or contrast-enhanced MRA. Transcranial Doppler (TCD) and transcranial colour Doppler (TCCD) are useful, rapid, noninvasive tools for the assessment of intracranial large arteries pathology. Due to the current lack of consensus regarding the use of TCD and TCCD in clinical practice, we systematically reviewed the literature for studies assessing the diagnostic accuracy of these techniques compared with intra-arterial IA, CTA, and MRA for the detection of intracranial stenosis and occlusion in people presenting with symptoms of ischaemic stroke.
To assess the diagnostic accuracy of TCD and TCCD for detecting stenosis and occlusion of intracranial large arteries in people with acute ischaemic stroke.
We limited our searches from January 1982 onwards as the transcranial Doppler technique was only introduced into clinical practice in the 1980s. We searched MEDLINE (Ovid) (from 1982 to 2018); Embase (Ovid) (from 1982 to 2018); Database of Abstracts of Reviews of Effects (DARE); and Health Technology Assessment Database (HTA) (from 1982 to 2018). Moreover, we perused the reference lists of all retrieved articles and of previously published relevant review articles, handsearched relevant conference proceedings, searched relevant websites, and contacted experts in the field.
We included all studies comparing TCD or TCCD (index tests) with IA, CTA, MRA, or contrast-enhanced MRA (reference standards) in people with acute ischaemic stroke, where all participants underwent both the index test and the reference standard within 24 hours of symptom onset. We included prospective cohort studies and randomised studies of test comparisons. We also considered retrospective studies eligible for inclusion where the original population sample was recruited prospectively but the results were analysed retrospectively.
At least two review authors independently screened the titles and abstracts identified by the search strategies, applied the inclusion criteria, extracted data, assessed methodological quality (using QUADAS-2), and investigated heterogeneity. We contacted study authors for missing data.
A comprehensive search of major relevant electronic databases (MEDLINE and Embase) from 1982 to 13 March 2018 yielded 13,534 articles, of which nine were deemed eligible for inclusion. The studies included a total of 493 participants. The mean age of included participants was 64.2 years (range 55.8 to 69.9 years). The proportion of men and women was similar across studies. Six studies recruited participants in Europe, one in south America, one in China, and one in Egypt. Risk of bias was high for participant selection but low for flow, timing, index and reference standard. The summary sensitivity and specificity estimates for TCD and TCCD were 95% (95% CI = 0.83 to 0.99) and 95% (95% CI = 0.90 to 0.98), respectively. Considering a prevalence of stenosis or occlusion of 42% (as reported in the literature), for every 1000 people who receive a TCD or TCCD test, stenosis or occlusion will be missed in 21 people (95% CI = 4 to 71) and 29 (95% CI = 12 to 58) will be wrongly diagnosed as harbouring an intracranial occlusion. However, there was substantial heterogeneity between studies, which was no longer evident when only occlusion of the MCA was considered, or when the analysis was limited to participants investigated within six hours. The performance of either TCD or TCCD in ruling in and ruling out a MCA occlusion was good. Limitations of this review were the small number of identified studies and the lack of data on the use of ultrasound contrast medium.