Ch. Arning . Department of Neurology, Allgemeines Krankenhaus (general hospital) Hamburg-Barmbeck
Is continuous wave Doppler sonography still of value in the diagnosis of extra-cranial vessel
disease?
Summary
The aim of this study was to assess the current value of extracranial continuous wave (cw) Doppler
sonography in routine use as compared to color-coded duplex sonography. For this purpose, 500 carotid
and 500 vertebral arteries were examined by a user experienced in both methods. The error rate of
Doppler sonography was determined only when the methods allowed a clear decision to be made about
the status of the vessel (normal findings including common variants, stenosis, and occlusion): In 85.4%
of the carotid arteries and 88% of the vertebral arteries, the Doppler findings fulfilled the diagnostic
differentiation unequivocally. For these cases, false findings were obtained in 1.9% of the carotid
arteries and 0.2% of the vertebral arteries. Accordingly, a clear Doppler sonographic finding, normal, or
pathologic, is still of large diagnostic value. However, ambiguous or uncertain findings requiring further
diagnostic workup are not uncommon. Thus, the sole use of cw Doppler sonography is no longer
sufficient in a stroke center but still retains its utility in the practitioner’s office.
Key words
Continuous wave (cw) Doppler sonography . color-coded duplex sonography . A. carotis interna .
A.vertebralis . false findings
Priv.-Doz. Dr. Ch. Arning
Neurologische Abteilung,
Allgemeines Krankenhaus Barmbeck,
D-22291 Hamburg,
E-Mail: christian.arning@t-online.de
T
he color-coded duplex sonography is the current method of choice for the diagnosis of
extracranial vessel disease: It allows for nuanced statements about significance, localization, and
morphology of vascular changes and has become the standard procedure within a short period of
time [15].
But cw Doppler sonography continues to be in use, partly for primary diagnostics in hospitals and often
as the sole method for extracranial vessels at the neurologist’s office. Although the validity of Dopplersonographic findings of the carotid artery has been documented impressively by several study groups [4,
7, 10, 14], Doppler sonography as the sole method for the diagnostic of extracranial vessel disease had
been abandoned by these study groups long ago [6, 9, 11].
False-positive findings of stenosis have to be expected with cw Doppler sonography in torturous vessels
[2] as well as false-negative findings in non-stenotic emboli sources [1]. The therapeutically important
differentiation between filiform stenosis and vessel occlusion remains uncertain [8]. With cw Doppler
sonography of the vertebral artery it is not possible to differentiate with certainty between a pathologic
situation or a harmless normal variation in cases of missing flow signal or slowed flow [5]. With colorcoded duplex sonography all these findings can be interpreted unambiguously as a rule.
Is the use of cw Doppler sonography today still justifiable regardless? How frequent is the occurrence of
false results with cw Doppler sonography really? What ranking does the Doppler sonography have in
comparison to the color-coded duplex sonography? Which Doppler findings require additional tests?
These questions were examined by comparing routine use of both methods at a department of
neurology, whereby the value of Doppler sonography as the sole method of the diagnosis of vessel
disease was examined. The advantages of Doppler sonography as an addition to duplex sonography,
especially in the exam of the periorbital arteries, are generally accepted. The aim of this study is
therefore the broader use of both methods in combination (e.g. examination of the periorbital arteries
and the subclavian artery with cw- Doppler sonography, evaluation of the carotid and vertebral arteries
with duplex sonography).
Method
Doppler and duplex sonography findings of 500 carotid and 500 vertebral arteries from routine testing
at the ultrasound laboratory of the department of neurology were included in the study. The study was
done on 250 consecutive patients by a user (DEGUM seminar leader, certified by the German Society for
Ultra Sonography in Medicine) very experienced in both methods.
A complete cw Doppler sonography (DWL Multi-Dop P, probes 4 and 8 MHz) with frequency spectrum
analysis was performed at first in all cases. The following vessels were compared side by side with the
usual technique [13, 15]: A. supratrochlearis, A. carotis communis, A. carotis interna, A. carotis externa,
A. vertebralis at the atlas loop and if possible at the origin as well as A. subclavia.
For each Doppler sonography finding it was determined if it allowed for a clear determination of the
vessel condition. The differentiation between normal finding including common variants, stenosis, and
vessel occlusion had to be unambiguous. All vessel findings with localized narrowing leading to
hemodynamic changes (from a degree of about 50-60% stenosis on) and principally detectable with
Doppler sonography were considered a stenosis.
In cases where the assignment of the Doppler sonography finding to one of the 3 categories was not
possible without ambiguity, the finding was rated as ambiguous/uncertain; a presumable diagnosis was
not sufficient. Hence a missing visualization of the internal carotid artery at its origin was labeled as an
ambiguous result even if direct signs of stenosis were missing (exclusion of a middle-grade stenosis is
with this constellation of findings not possible). Likewise, the typical findings for an occluded internal
carotid artery were always rated as ambiguous since the possibility for a differential diagnosis of filiform
stenosis exists. A unilateral slowing of the vertebral artery flow was always, even with a normal pulse
curve, rates as an inconclusive finding since a common variant can only be determined with certainty if
the lumen diameter is known and, alternatively, a pathologic situation could exist. Table 1 shows all
findings that were classified as ambiguous for the carotid and vertebral arteries.
Table 1
Findings with cw Doppler sonography classified as ambiguousa
A. carotis
A. carotis interna not visualized at its origin
A.carotis communis not visualized
Questionable stenosis finding of the A. carotis interna (DDx torturous vessel)
Questionable finding of a pathologic increase of flow (AV-fistula?)
A. vertebralis
A. vertebralis not visualized
A. vertebralis not unequivocally identifiable
A. vertebralis slowed unilaterally
Questionable stenosis finding at the origin (finding ambiguous)
___________________________________________________________________________________________
a
Differentiation between normal finding (including common variant), stenosis, and vessel occlusion not possible
Doppler sonography was followed by color duplex sonography (Acuson 128 XP 10, standard probe L5,
nominal frequency of 5 MHz). The following vessels were examined with the usual technique [3, 13, 15]:
A. carotis communis, A. carotis interna, and A. carotis externa bilaterally each as well as the A.
vertebralis in the 1st and 2nd segment bilaterally. The criteria published by us in 1999 [3] were used for
the duplex-sonographic diagnosis of stenoses, occlusions, and normal variants.
The results of Doppler and duplex sonography were compared. If there were deviations between the
methods and an unambiguous result of the cw Doppler sonography, the Doppler result was regarded as
a false finding. The reference method duplex sonography delivered an unambiguous result in all cases. It
was always attempted to detect the cause of the false Doppler findings.
In cases classified as ambiguous after the Doppler sonography, the duplex findings were consulted to
determine the frequency of important pathologic results compared to harmless common variants.
Results
Table 2 shows the frequency of unambiguous and ambiguous/uncertain diagnoses with Doppler
sonography of the carotid and vertebral artery: An unambiguous finding for the vessel (normal finding
including common variants, stenosis, and occlusion) could be determined for the carotid artery in more
than 85% of the cases and in more than 88% of the cases for the vertebral artery.
Table 2
Frequency of unambiguous and uncertain/ambiguous diagnoses with Doppler sonography of the A.
carotis and A. vertebralis (n=500)
Diagnosis unambiguousa
___________________
[n]
[%]
Diagnosis uncertain/ambiguous
__________________________
[n]
[%]
_______________________________________________________________________________
A. carotis
427
85.4
73
14.6
A. vertebralis
440
88.0
60
12.0
_________________________________________________________________________________________
a
Reliable differentiation possible between normal finding (including common variant), stenosis, and occlusion
The rate of false results with the cw Doppler sonography is very low, with a total of 1.9% for the carotid
artery and 0.2% for the vertebral artery if only the findings determined to be unambiguous by the
examiner are considered (table 3). Causes for the false-negative findings for the carotid artery were
unrecognized low- to mid-grade stenoses, for the vertebral artery collateralized vessel occlusions. One
false-positive case for the carotid artery occurred because of collateral flow increased with a contralateral occlusion.
Table 3
False findings with cw Doppler sonography of the A. carotis and A. vertebralisa
Findings with
False findings
False findings
clear diagnosis
[n]
[n]
[%]
______________________________________________________________________________________
A. carotis
Normal finding
397
7
1.8
Pathologic finding
30
1
3.3
Findings total
429
8
1.9
A. vertebralis
Normal finding
438
1
0.2
Pathologic finding
2
0
0
Findings total
440
1
0.2
_______________________________________________________________________________________
a
Without consideration of ambiguous/uncertain findings
All the findings for the carotid and vertebral artery classified as ambiguous/uncertain with Doppler
sonography were able to be clarified with duplex sonography (table 4).
Table 4
Causes of uncertain/ambiguous findings with cw Doppler sonography (n+500) after resolution with
color-coded duplex sonography
Doppler sonography
[%]
Color-coded duplex sonography
[%]
__________________________________________________________________________________________
ACI origins segment not visualized
10.8
Dorso-medial origins variant
4.6
Vessel occlusion
4.4
Filiform stenosis (proximal)
0.8
Slowing of flow in occlusion/distal stenosis 1
ACC not visualized
0.8
Occlusion
Pathway anomaly (loop formation)
0.6
0.2
ACI: questionable stenosis (DDx torturous
vessel)
2.8
Stenosis
Torturous vessel
Increased flow
1.2
1.2
0.2
ACI: questionable pathologic increase in flow
(AV-fistula?)
0.2
AV-fistula
0.2
AVT origins not visualized
4.6
Hypoplasia
Vessel occlusion
Slowing of flow in proximal disturbance
Slowing of flow in distal disturbance
Unremarkable (poor test conditions)
1.8
2.0
0.2
0.2
0.4
AVT not distinctly identifiable
1.8
AVT unilaterally slowed, normal pulsatility
1.8
Hypoplasia
Unremarkable (poor test conditions)
Hypoplasia
Proximal occlusion
0.6
1.2
1.6
0.2
Hypoplasia
Distal disturbance
1.4
1.8
Proximal stenosis
Proximal occlusion
0.2
0.2
AVT unilaterally slowed, increased pulsatility
AVT unilaterally slowed, reduced pulsatility
1.4
AVT: questionable stenosis finding at origin
0.2
Stenosis at origin
0.2
__________________________________________________________________________________________
ACI A.carotis interna, ACC A. carotis communis, AVT A. vertebralis
Discussion
The study shows that cw Doppler sonography has a very low error rate as long as it delivers an
unequivocal and certain finding, either normal or pathologic, from the hand of an experienced user. A
routine duplex sonography is not necessary in such cases. In the evaluation of the determined error rate
it is to be considered that the definition of “ambiguous or uncertain finding” was kept very broad here.
All constellations that would allow any different, also rather improbable, diagnoses were included. For
example, even the typical constellation of findings for internal carotid artery occlusion was considered
uncertain because of the possibility of the filiform stenosis as differential diagnosis. If the Doppler
sonography finding would have been evaluated as a definite occlusion, which is possible with a
predictive value of 90% [13], four significant false results would have occurred in our collective in this
manner.
The same is valid for other constellations of findings in the carotid or vertebral artery. With a missing
flow signal or slowed flow in the vertebral artery, it cannot be clearly differentiated with cw Doppler
sonography if it is a pathologic situation or a common variant [5]. However, this differentiation is of
certain relevance; therefore, all similar findings must be rated as “uncertain”.
The rate of false findings in the carotid artery and especially in the vertebral artery would be significantly
higher if all – even uncertain – Doppler sonography findings would be part of the equation. The
experienced examiner would be able to prove “most” clinically relevant findings if cw Doppler
sonography would be solely available, but this is not enough for today’s demand of a sophisticated
vascular diagnostic.
The relatively high rate of ambiguous and uncertain findings in our study, 14.6% with the carotid artery
and 12% with the vertebral artery, can be explained by about 50% with variations in pathway and caliber
of the vessels as well as pathologic vascular changes. In a collective with a greater share of normal
findings, possibly at a neurologist’s office, one should expect less ambiguous cases than in our study
population. A department of neurology with a “stroke focus” on the other hand, has to expect a
comparatively rate of ambiguous cases, requiring further clarification with duplex sonography. In such
an environment the color-coded duplex sonography is certainly the method of choice in primary
diagnostics.
Outside of facilities serving the acute diagnostics of stokes, the use of cw Doppler sonography appears
justified to this day as long as there is an option to clarify uncertain findings with duplex sonography.
Clinical relevance certainly needs to be considered because further investigation is not required in all
cases of ambiguous or uncertain Doppler sonography findings. If, for example, hemodynamically
relevant stenoses must be excluded prior to a cardio-surgical intervention, the detailed search for an
emboli source is not necessary.
The numbers determined here regarding the error rate of cw Doppler sonography are valid for the
experienced examiner; the dependence of the results on the qualifications of the examiner and the
difficulties learning the methods are well-known [12].
Conclusions
Continuous wave Doppler sonography of the carotid and vertebral artery is a valuable method for the
experienced examiner. Such findings always have a great validity when they are clear and unambiguous,
either normal or pathologic. But ambiguous and uncertain findings occur in a significant share of cases,
demanding further diagnostics. The application appears therefore only to make sense if there is a
possibility to resolve uncertain findings with duplex sonography.
Half of the uncertain findings are caused by anatomical variants and by pathologic changes.
Complementary diagnostic will therefore be necessary more frequently; the sooner relevant pathologic
findings can be expected. For this reason, cw Doppler sonography alone is not sufficient for a stroke
center. In the practitioner’s office, on the other hand, it still retains its utility.
Literature
1. Arning C, Hermann HD (1988) Floating thrombus in the internal carotid artery disclosed by B-module
ultrasonography. J Neurol 235: 425-427
2. Arning C (1994) False diagnosis carotid stenosis in conventional Doppler sonography. Causes of false diagnoses
with use in clinic and practice. Ultraschall Klin. Prax 9: 144-148
3. Arning C (1999) Color-coded duplex sonography of the arteries supplying the brain. A text-picture atlas of
methodical foundations, normal and pathologic findings, 2. Aufl. Thieme, Stuttgart
4. Daffershofer M, Hennerici M (1990) Spectrum analysis of Doppler signals. Ultraschall Med 11: 219-26
5. Delcker A. Diener HC (1992) The different ultrasound methods for examining A. vertebralis – a comparing
evaluation. Ultraschall Med 13: 213-220
6. Delcker A, Diener HC, Timmann D, Faustmann P (1993) The role of vertebral and internal carotid artery disease
in the pathogenesis of vertebrobasilar transient ischemic attacks. Eur Arch Psychiatry Clin Neurosci 242: 179-183
7. Diener HC, Dichgans J, Voigt K (1981) Functional anatomy of extracranial arteries in occlusive vascular disease by
direct continues wave Doppler sonography. Cadiovasc Intervent Radiol 4: 193-201
8. Görtler M, Niethammer R, Widder B (1994) Differentiating subtotal carotid artery stenoses from occlusion by
colour-coded duplex sonography. J Neurol 241: 301-305
9. Hennerici MG, Meairs SP (1999) Cerebrovascular ultrasound. Curr Opin Neurol 12: 57-63
10. Neuerburg-Heusler D (1984) Doppler sonographic diagnostic in extracranial occlusive disease. Validity of
direct, indirect, and combined methods. Vasa (Suppl 12): 59-70
11. Neuerburg-Heusler D, Hennerici MG (1999) Vascular diagnostic with ultrasound, 3. Aufl. Thieme, Stuttgart
12. Reutern GM von (1982) Thoughts for the education in ultrasound diagnostic in brain-supplying arteries.
Ultraschall 3: 58-60
13. Reutern GM von, Kaps M, Büdingen HJ von (2000) Ultrasound diagnostic of brain-supplying arteries. 3. Aufl.
Thieme, Stuttgart
14. Trockel U, Hennerici M, Aulich A, Sandmann W (1984) The superiority of combined continuous wave Doppler
examination over periorbital Doppler for the detection of extracranial carotid disease. J Neurol Neurosurg
Psychiatry 47: 43-50
15. Widder B (1999) Doppler and duplex sonography of brain-supplying arteries, 5. Aufl. Springer, Berlin Heidelberg