ORIGINAL ARTICLE
The importance of Doppler studies in asymptomatic
intracranial and extracranial arterial disease
Peter Hermes
2nd Division of Neurology, Prof G Arnetoli, Carreggi Hospital, Florence, Italy(Received for publication on March 25, 2002)

Abstract. Knowledge of intracranial and carotid disease in the symptomatic and especially theasymptomatic high risk population may be useful for evaluating future treatment modalities. A groupof 204 symptomatic patients and 105 asymptomatic elderly patients at high risk for stroke were tested
by carotid duplex ultrasound and transcranial doppler for the presence of carotid and intracranialstenosis. Quantitative measurements of the stenosis were made directly from the hard copy of the carotid duplex and the transcranial doppler. Of the 204 symptomatic patients 168 (83%) had some degreeof stenosis: 84 of the 204 (41%) in the intracranial circulation only, 59 (29%) in the internal carotid
only, and 26 (13%) in both sets of vessels. Of the asymptomatic patients 85 (81%) had some degree ofstenosis; 31 of 105 (30%) in the intracranial circulation only, 35 (33%) in the internal carotid only, and19 (18%) in both sets of vessels. Statistical analysis did not reveal signiﬁcant differences between thetwo groups. The large percentage of intracranial disease in the symptomatic as well as the asymptomatic population at high risk for stroke require further conﬁrmation by good duplex studies of theintracranial circulation. This is important in order to create coherent treatment protocols. (Keio J Med
51 (4): 189–192, December 2002)
Key words: transient ischemic attack, transcranial Doppler

Introduction
Stroke prevention is of paramount importance.1 TheNorth American Symptomatic Carotid Artery Endarterectomy Trial (NASCET) study2 and the Asymptomatic Carotid Artery Stenosis (ACAS) study3 among
others have addressed the issues of identying patientswith carotid stenosis most at risk for stroke and in needof intervention. Both studies examined the effects ofpharmacologic and surgical therapy of the extracranial
carotid system on the mortality and morbidity resulting
from ischemia. A few studies of intracranial circulationin symptomatic patients are on record,4,5 and studies
on abnormalities of intracranial circulation in high risk
asymptomatic patients have been recently reported.6The question asked in this study concerned is the incidence of intracranial vessel abnormalities in a symptomatic group of patients as deﬁnied below versus anasymptomatic group.
We compared the intracranial and extracranial Doppler ﬁndings in an elderly group of asymptomatic high-risk and symptomatic patients. We then compared
the prognostic implication of these sonographic ﬁndings with the prognostic implications of the modiﬁed
Framingham questionnaire7,8 (a one page document
modiﬁed by Wolf and this author which interrogates thevarious risk factors of a potential candidate study. SeeAppendix A) and the history of stroke-TIA and/orcarotid bruits. The Framingham questionnaire was
modiﬁed for this study by the addition of four additional risk factors: alcohol consumption, family historyof stroke, elevated cholesterol >200 and overweight.
Each added factor was assigned a maximum weight of 2
points equivalent to the weight points of other risk factor. The cut-off scores as described in the Framingham
questionnaire were adjusted upward by A25% to reﬂect
the increase in total possible score adding these new 4factors.
Although the study population does not reﬂect theepidemiologic incidence of stroke risk and symptomatology in the general population, the conclusions of thisstudy regarding the utility of Doppler sonography in theReprint requests to: Dr. Peter Hermes, 9 Via Guicciardini, Apt. 9, 50125 Firenze, Italy
189

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Hermes P: Carotid and cerebral ﬂow abnormalities in seniors

better identiﬁcation of elderly patients at risk for stroke
remain valid.
Material and Methods
Patients were culled from a population of seniors
who were living in retirement centers in New Yorkstate and were attending stroke prevention programs
presented as part of a health care symposia between
1993 and 1996. Attendees ﬁlled out a risk assessment
questionnaire, which was subsequently reviewed with aphysician.
High risk but asymptomatic patients were deﬁniedin accordance with the modiﬁed Framingham clinicalassessment criteria8 as discussed above. Risk factors
included hypertension (BP > 140/90); cardiovasculardisease including a history of MI, angina, atrial ﬁbrillation; peripheral vascular disease; excessive alcohol9 (>2glasses per day); history of smoking (>40 packs/year);diabetes mellitus; cholesterol >200 mg/dl; and excess
weight.10 Patients were considered to have a 50% orgreater chance of incurring a stroke if the accumulated
score exceeded 23 for males and 22 for females on themodiﬁed Framingham scale (similar to the Framingham
Score). Symptomatic patients were deﬁnied for thisstudy as those with a history of transient ischemic attack, stroke, or carotid bruits. Patients who met thesecriteria were invited to join the study.
Of the 309 patient studied, 204 (66%) were symptomatic, and 105 (34%) were asymptomatic high-risk.
Carotid duplex (Biosound) and transcranial Doppler(Medasonic) sonography were performed by vasculartechnicians on these 309 patients and the results of thetwo groups were compared. Results were evaluated by
the author (PH), a clinician with 12 years experience induplex interpretation.
The abnormalities of the carotid arteries were deﬁnied by the degree of stenosis at the site of maximum
plaque dimension and compared to the arterial diameter before the stenosis as suggested by Taylor andStrandness.11 Patients were categorized into one ofthree groups based on the degree of stenosis: less than
50% reduction in diameter, 50–70% reduction, andmore than 70% reduction.
Intervals were based on the indications for medical
therapy (>50% stenosis) and surgery (>70% stenosis).
Plaque size was measured with a caliper calibrated inmillimeters directly from the hard copy generated by
the duplex. Although Doppler ﬂow velocities wereobtained in each case we chose to measure arterial caliber diameter just as performed in the ACAS3 study.
Abnormal intracranial circulation was deﬁned as a
50% or more change (decrease or increase) in the ﬂow
velocity (in cm/sec) in the middle cerebral artery compared to the normal fellow artery,12 or total absence of

the arterial signal on one side. Normal values wereobtained from the study of Hansen et al.13 Statisticalanalysis was performed using the Wilcoxon-MannWhitney test (StatXact 3 for Windows, Cytel Software
Corporation, Cambridge, Mass.).
Results
Of the 204 symptomatic patients, 169 (83%) had
some degree of stenosis: 84 of 204 (41%) in the intracranial circulation only, 59 (29%) in the internal carotid
only, and 26 (13%) in both sets of vessels (Fig. 1),
intracranial circulation abnormalities were therefore
more common than extracranial circulation disease inthis group.
Of the 105 asymptomatic patients, 85 (81%) had
some degree of stenosis: 31 of 105 (30%) in the intracranial circulation only, 35 (33%) in both sets of carotid
only, and 19 (18%) in both sets of vessels (Fig. 2).

Fig. 1Results of Doppler studies in 204 symptomatic patients.

Fig. 2

Results of Doppler studies in 104 asymptomatic patients.

Keio J Med 2002; 51 (4): 189–192

Fig. 3Severity of carotid stenosis in 59 symptomatic paitents.

Fig. 4

Severity of carotid stenosis in 35 asympotomatic patients.

The Wilcoxon-Mann-Whitney test was used tocompare the frequency of stenosis in symptomatic
versus high-risk asymptomatic patients. The test revealed no signiﬁcant difference between the two groups(Mann-Whitney statistic ¼ 2:767  104, p ¼ 0.4648).
These data indicate that the lack of symptoms does notindicate an absence of arterial disease. Furthermore,
the likelihood of ﬁnding stenosis in a high-risk asymptomatic patient is signiﬁcant.
We then compared the degree of stenosis in the 59
symptomatic and 35 asymptomatic patients with only
carotid stenosis. We found less than 50% stenosis in
more than half the cases in both symptomatic andasymptomatic groups. Stenosis of 50–70% was found in
27% of symptomatic patients, and 40% of asymptomatic patients. Nineteen percent of symptomatic patients, but no asymptomatic patients, had stenosis morethan 70% (Figs. 3, 4).
Discussion
The ﬁndings of this study corroborate the ﬁndings of
the ACAS study3 regarding the presence of carotid191

disease in asymptomatic patients with risk factors, inparticular that asymptomatic patients with multiple risk
factors may have as much or more carotid stenosis as
symptomatic patients. Importantly, this study extends
this concept to the intracranial circulation, showing thepresence of intracranial abnormalities in asymptomatic
high-risk patients. Furthermore, these data help tofurther establish the usefulness of the modiﬁed Framingham questionnaire for identifying this high risk‘‘asymptomatic population’’.
Of the symptomatic patients within this study, 41%
had intracranial disease vs. 29% with carotid disease(see Fig. 1 p > 0,05). The fact that patients with symptomatic carotid disease have 30% more intracranialstenosis is surprising. This may be partially accounted
for by the extracranial artery disease stenosis which
may cause increased intracranial ﬂow.14 It is also important to note that the NASCET subset analysis has
found intracranial artery stenosis an independent risk
factor for stroke in patients with carotid stenosis.15
If the above ﬁndings are corroborated in large
studies it may become critical to use antiplatelet therapy in intracranial stenosis grater than 50% even if theextracranial circulation is normal.
Furthermore our ﬁndings demonstrated the presenceof intracranial abnormalities in asymptomatic patientseven without carotid abnormalities. The large percentage of abnormal intracranial or extracranial arteries in
the asymptomatic population was surprising. In thisgroup the combined rate of abnormalities was 81% withequal distribution between the intracranial and carotid
circulation. This is much higher than reported previously.16,17 Nevertheless intracranial artery stenosis isa dynamic lesion which can both progress and regress.18
A number of studies have described various therapeutic modalities in intracranial symptomatic stenosis.19–21 A small number of patients were mainly
treated with anticoagulation. These are uncontrolled
studies and although widely used in the medical andneurological practice lack supporting hard data.
In our study only the velocity shift of the middle
cerebral artery was analysed. A number of medical
conditions can cause marked changes in the velocity
shift such as anemia, increased viscosity, or congestive
heart failure. Usually, these conditions cause bilateralchanges. Furthermore, tandem stenosis and concomitant extracranial stenosis may alter TCD results.22 Until the B-mode results of intracranial circulation become
more sophisticated, a clear-cut reading of the arterial
wall abnormalities is difﬁcult.23 Intra-arterial ultrasound has become available24 for the carotid artery but
its use in the intracranial vessels has not yet been published. Although a very good correlation and up to 90%
sensitivity and speciﬁcity are reported between angiography and carotid Duplex,22 such a correlation has not192

Hermes P: Carotid and cerebral ﬂow abnormalities in seniors

been shown between angiography and transcranialDoppler. With the advent of good B-mode studies of
intracranial circulation,23 validation studies should beforthcoming.
The large percentage of intracranial disease in thesymptomatic population as well as the asymptomaticpopulation at high risk, surprisingly high in our study,requires further conﬁrmation by good Duplex studiesof the intracranial circulation, conﬁrmed by angiography.14,24 Randomized treatment studies for intracranial circulation stenosis may follow. This is important since there is no recognized therapeutic protocol
for intracranial vascular disease with solid supporting
data and since a large segment of the at-risk population
may beneﬁt from available medical or surgical therapeutics.25–27
Although ultimate clinical outcomes over an extended period of time are not known for this patientgroup at this time, the ﬁndings reported are signiﬁcantin and of themselves, as they suggest that these diagnostic tests are useful and may increase the clinician’sability to identify patients in whom intervention might
be warranted.

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