RADIONUCLIDE CBF AND CAROTID ANGIOGRAM/Foo et al.
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territory. Despite perfusion pressures calculated at 110 cm
H2O and less, we were unable to demonstrate profound
capillary collapse, even in areas at high risk to the "noreflow phenomenon" such as thalamus and basal ganglia. In
addition, Chiang et al.5 probably infused their fixative
against a much higher cerebrovascular resistance because, in
their experiments, the cerebral vasculature had been filled
with blood during ischemia, the viscosity of which was undoubtedly increased as a result of the stasis.4 Thus, it is
highly likely that the fixative perfusions of Chiang et al. occurred at pressures and flow rates considerably less than
those of the present experiments.
The possibility remains that the absence of the formed
elements of the blood (red cells, white cells and platelets)
from the lumina of the ischemic capillaries might have
prevented the endothelial and glial changes from occurring
in our experiments. If substances released by these structures are instrumental in causing the pathology in question,
they would operate equally in all areas of the brain rather
than preferentially in selected areas which is the pattern of
the "no-reflow phenomenon."
Although the current experiments cannot relate the
changes in ischemic cerebral capillaries to postischemic
neurological function, we believe that they provide a more
accurate picture of the structural state of the ischemic
capillaries than was previously offered.5 Although glial
swelling previously seemed to obstruct red cell passage
through capillaries within 15 minutes of ischemia, we agree
with others that this seems doubtful," as it is quite unlikely
39
that the glial swelling and capillary luminal narrowing found
in the present experiments would present an absolute barrier
to the flow of red cells. We feel that the impaired flow noted
in acute experimental ischemic models1"3- ••10 therefore must
be better explained by mechanisms other than pericapillary
glial swelling, such as precapillary shunting, increased blood
viscosity due to red cell settling' or vascular constriction.10
References
1. Ames A III, Wright RL, Kowada MD, et al: Cerebral ischemia. II. Noreflow phenomenon. Am J Path 52: 437-453, 1968
2. Ginsberg MD, Myers RE: The topography of impaired microvascular
perfusion in the primate brain following total circulatory arrest.
Neurology 22: 998-1011, 1972
3. Fischer EG, Ames A III: Studies on mechanisms of impairment of cerebral circulation following ischemia: Effect of hemodilution and perfusion
pressure. Stroke 3: 538-542, 1972
4. Merrill EW: Rheology of blood. Physiol Rev 49: 863-888, 1969
5. Chiang J, Kowada MD, Ames A III, et al: Cerebral ischemia. III.
Vascular changes. Am J Path 52: 455-476, 1968
6. Cantu RC, Ames A III: Distribution of vascular lesions caused by cerebral ischemia. Relation to survival. Neurology (Minneap) 19: 128-132,
1969
7. Peters A: The fixation of central nervous system. In Nauta WJH,
Ebbesson SOE (eds): Contemporary Research Methods in Neuroanatomy. New York, Springer-Verlag, pp 56-76, 1970
8. Siegel S: Non-Parametric Statistics for the Behavioral Sciences. New
York, McGraw Hill Book Co, p 279, 1956
9. Olsson Y, Crowell RM, Klatzo I: The blood-brain barrier to protein
tracers in focal cerebral ischemia and infarction caused by occlusion of
the middle cerebral artery. Acta Neuropath (Berl) 18: 89-102, 1971
10. Wade JG, Amtorp O, SjJrenson S: No-flow state following cerebral
ischemia. Arch Neurol 32: 381-384, 1975
11. Cuypers J, Matakas F: The effect of postischemic hyperemia on intracranial pressure and the no-reflow phenomenon. Acta Neuropath (Berl)
29: 73-84, 1974
Radionuclide Cerebral Blood Flow and Carotid
Angiogram
Correlation in Internal Carotid Artery Disease
DOMINIC FOO,
M.D.,*
AND LYNN HENRICKSON,
M.D.f
S U M M A R Y Radionuclide cerebral blood flow (CBF) examinations of 48 patients with atherosclerosis, 18 with occlusion and
30 with stenosis of the internal carotid artery (ICA) were correlated
with their respective cerebral angiograms.
The following results were obtained. Flow was visually unilaterally
diminished in 29 (60%) of 48 patients, including 14 (78%) with occlusion
and IS (50%) with stenosis. Sixty-two percent of the subjects with severe
stenoses and 46% of the patients with mild stenoses had a positive flow
study. Diminished flow was evident in the neck in 80% of the patients,
intracranially in 20%. Positive radionuclide angiograms always pointed
to the side with occlusion or the greater degree of stenosis even though
bilateral internal carotid disease was frequently found (54%). The data
leading to the differentiation between major and minor ICA stenosis are
not sufficient to justify any conclusion.
Introduction
FISHER 1 ' 2 mentioned his experience with the autopsy findings in 200 cases of cerebrovascular accident clinically
suspected of having middle cerebral artery (MCA) throm-
bosis in which he failed to find any such thrombosis. Nor
was he able to locate the source of cerebral emboli in many
cases with postmortem examinations. By a systematic investigation of the cervical portion of the carotid arteries at
autopsy and by carrying out a thorough clinicopathological
correlation, he established the role of internal carotid artery
(ICA) disease as a major cause of ischemic stroke.
Brain scanning was introduced by Moore in 1948. Subsequently, the development of the scintillation camera allowed
the use of dynamic evaluation of radioisotope movement
•Neurobehavior Unit, VA Hospital, 150 South Huntington- Avenue,
Boston, Massachusetts 02130.
tDepartment of Radiology, VA Hospital, Minneapolis, Minnesota 55417;
and the University of Minnesota Department of Radiology, Minneapolis,
Minnesota 55455.
This study was supported in part by the Research Department of the VA
Hospital, Minneapolis, Minnesota 55417.
STROKE
40
Downloaded from http://stroke.ahajournals.org/ by guest on June 16, 2017
through the carotid and cerebral arteries. 3 Radionuclide
cerebral blood flow (CBF) has been used widely since its introduction in 1966.4 There have been several excellent
reviews of this subject which describe the radionuclide
angiographical results in cerebrovascular disease.5"7
In experiments with dogs and with square-wave electromagnetic flowmeters,8 critical stenosis was determined for
the canine common carotid artery (CCA) with some of the
cervical vessels occluded. In a similar study in conscious
humans with intracranial berry aneurysms whose CCAs
were to be ligated, Brice et al.9 determined the critical
stenosis when a significant decrease in carotid blood flow occurred. Mann et al.,10 in their experiments with dogs, estimated that the area of the arterial lumen might be reduced
90% before 50% reduction in blood flow occurred. Fischer et
al.5 estimated that the radionuclide angiography would be
abnormal if the carotid stenosis was greater than 50%.
The exact diagnosis of ICA lesions rests on the carotid
angiogram or autopsy, but clinical features serve to distinguish most cases. As mentioned by Fisher,1 hemiplegia of
unknown cause in persons in the younger age group and
absence of the carotid pulse at the acute phase of stroke are
highly diagnostic. However, in some cases the clinical picture is atypical and additional investigation is required to establish the diagnosis. Brain scanning frequently locates the
site and estimates the size of cerebral infarct. Serial scanning sometimes can differentiate stroke from brain tumor.
In many cases of cerebral infarction, the dynamic flow study
is positive while the static views are still negative shortly
after stroke. Animal and human experiments 8 ' 9 have
demonstrated a certain correlation between the degree of
ICA stenosis and decreased carotid blood flow. Many
reports in the past 1115 have demonstrated the use of the
radionuclide CBF technique in the diagnosis of carotid lesion. As it is easily available and noninvasive, it has been
widely used in the evaluation of patients with strokes,
ischemic and nonischemic, together with the static images.
In the previous English literature, there were not many
large studies using this method to evaluate ICA disease.
T.MiiiK 1 Number of Cases Not Included in This Study
(1)
93 cases of carotid angiograms
!•">
ICA stenosis <2.">9r*
ICA stenosis without available radionuclide
flow study
2.'!
ICA occlusion without available radionuclide
study
29
Bilateral ICA occlusion with poor flow study
:•{
CCA occlusion
'•>
Occlusion of cavernous ICA with cervical stenosis J
Stenosis of cavernous ICA with cervical stenosis
I
MCA occlusion with cervical stenosis of ICA
.'!
ICA occlusion with severe stenosis of
eontralateral F.CA
1
ICA stenosis with poor radioiniclide study
4
ICA stenosis with equivocal radionuclide study
2
>."> months between nuclear and contrast
angiograms
S
(2)
1.', cases of radionuclide flmv studies
flow
Kquivoeal asymmetry of radionuclide
ICA stenoses with poor
flow
>."> months between nuclear and contrast
angiograms
•For 197o, please see Methods of text.
2
4
X
VOL 8, No
1, JANUARY-FEBRUARY
1977
Jhingram et al.,4 Griep et al.,8 and Bell16 found a high correlation between ICA occlusion and the result of the
radionuclide study. However, apart from the study by Griep
et al., few reports compare the results of radionuclide studies
with the degree of ICA stenosis.
Some authors12' "• 1? did not find any significant correlation between the site of obstruction of the ICA and the site
of the diminished activity in the radionuclide CBF. However, there was no large study of this sort of comparison.
Many of the reviewed studies were only case reports. In addition, bilateral carotid artery disease is quite frequent.18
The role of the radionuclide study in bilateral ICA lesions
has not been adequately evaluated as well apart from
bilateral ICA occlusion in which the isotope study is usually
poor.
The purpose of this study is to correlate the radionuclide
CBF with the findings at bilateral carotid angiography in
ICA lesions limited to the cervical region only. Attempts
were made to (1) compare the result of the radionuclide
study between ICA occlusion and stenosis of varying
severity, (2) correlate the site of ICA lesion proved at cerebral angiography and the site of diminished activity in the
radionuclide study, and (3) evaluate the role of the radionuclide study in bilateral ICA lesions.
Methods
Bilateral carotid angiograms performed at the
Minneapolis Veterans Administration Hospital in the last
five-year period were reviewed. During the period 1971 to
1974, only stenoses greater than 25% were consistently
recorded in the radiology files. During 1975, ICA stenoses of
all degrees of severity were recorded. Therefore, those cerebral angiograms with ICA stenosis less than 25% were not
selected. A total of 141 bilateral carotid angiograms were
reviewed. Of these, 48 were selected because the ICA lesion
was limited to the cervical region and the corresponding
dynamic flow studies of the brain scan were available. In
these 48 cases, there were no significant lesions in the CCA,
MCA, ACA or other portions of the internal carotid artery
beyond the cervical region. Bilateral ICA occlusions were
also excluded. The other 93 studies were not considered
(table 1), including 52 ICA lesions without available radionuclide blood flow examinations, three bilateral ICA
occlusions, three CCA occlusions, two ICA lesions in the intracavernous portion of the vessel, three mainstem MCA
occlusions and one ICA occlusion with additional severe external carotid artery disease on the opposite side. In eight
cases, the time interval between the carotid angiogram and
radionuclide study was greater than five months. These cases
were also excluded. Another six subjects with ICA stenoses
were excluded because of poor radionuclide flow or
equivocal asymmetry of flow.
In this study, the terms "radionuclide cerebral blood
flow," "dynamic flow study" and "radionuclide angiogram" are used interchangeably.
ICA stenosis was defined as narrowing of the arterial
lumen less than 100%. The degree of the ICA stenosis was
graded in accordance with the criteria in the article on cerebral infarction by Alter et al.19 Lesions were classified as
severe with 90% to 99% stenosis, moderate with 507o to 89%
stenosis, and mild with 25% to 49% stenosis. ICA occlusion
RADIONUCLIDE CBF AND CAROTID ANGIOGRAM/Foo et al.
TAHLIC 2
Itadionuelide CBF in /,S Cases of
Proved ICA
Angiographicalli)
Lesions
Type of ICA lesion
Occlusion
Stenosis
Total
Normal
4 (22'/;)
i.-)(.-)<)'•;)
19(40'V)
Abnormal*
c
14 (78 :;)
io(.-)0<;;)
29 (60':;)
Total
IS
30
4S
•Diminished railioisotope perfusion on one side.
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I'ailioniirliilf
CBF in 10 Cases of A ngioyrtiphicalh/
Proved ICA Stenoses of Varying Severity
Severity of ICA stenosis
N orma!
Abnormal*
Total
Severe (00-99 )f
Moderate (."iO-SO)
.Mild (2.V40)
Total
."> (38)f
. » (7.-.)
i:j
7 r>4)
8 (62)
I (2.1)
6 (46)
l.'i (•"><>)
1.") (.">())
30
•Diminished radioisotope perfnsion on one side.
"("Numbers in parentheses are percent.
Correlation Between, Site of Abnormal
Radionuclide
CBF and Angiographically
1'roved ICA Lesion in 2!) Cases
Type of ICA lesion
Neck*
Headt
Total
J0(71)i
13 (87)
23 (80)
4 (29)
2 (L3)
6 (20)
14
1.")
Occlusion
Stenosis
Total
29
•Diminished radioisotope perfusion in the carotid area.
fDiminished radioisotope perfusion in the MCA area.
{Numbers in parentheses are percent.
was defined as obliteration of the lumen of the artery. The
authors examined the dynamic flow studies of the brain scan
together for evidence of unilaterally decreased radioisotope
activity in the region of the neck or the head in the distribution of the MCA. Rosenthall15 defined five patterns of perfusion in the radionuclide cerebral angiogram in patients with
intracranial disease. Four of these patterns referred to
changes resulting from brain tumors and the remaining
pattern to diminished perfusion of the afflicted cerebral
hemisphere. Strauss et al.20 stated that asymmetry of the distribution of the tracer was the most important criterion in
the interpretation of the nuclear angiogram. In this study
only anterior images were examined. A normal radionuclide study meant that the radioactivity in the distribution
of the major cerebral blood vessels was equal bilaterally.
The study was positive or abnormal if there was definite
asymmetry of radioactivity. If visualization of radioactivity
in the neck and head was unsatisfactory, the study was
designated poor and was excluded.
No attempt was made to quantify the degree of
diminished radioisotope activity in the abnormal studies as
our analysis was only visual. Undoubtedly, the quantitative
analysis of the radionuclide angiogram increases its sensitivity in detecting ICA lesions by comparing the slope of
activity with time over the cervical carotid region.21
Similarly, the activity or time differential of radioisotope activity and the "hemispheric retention phenomenon" from
delayed arterial or venous visualization were not chosen as
criteria in our study. Criteria used in our study were clear
visualization of the radioactivity in the neck and in the head
in the distribution of the MCA and distinct asymmetry
between the activity bilaterally. The side with diminished activity was considered abnormal or positive. This asymmetry
was found most strikingly on the first scintiphoto following
the appearance of tracer. Therefore, only the first scintiphotos of the anterior flow images following appearance of
radioactivity was examined for asymmetry in the neck and
head. Two cases with equivocal asymmetry, four with poor
flow and eight with a greater than five-month interval
between contrast and radionuclide angiograms were excluded (table 1, part 2).
Forty-eight cases were eventually selected. The time interval between all the radionuclide and carotid angiograms was
within six weeks, i.e., within one week in 23 cases, two weeks
T.MU.I: .'!
TABLK 4
41
4
i:;
in 20 cases, and greater than two weeks in five cases. Neurosurgical records confirmed that no patients underwent endarterectomy between the radionuclide and contrast angiogram. The carotid angiograms were reviewed independent of
the radionuclide study.
No attempt was made to correlate the degree of angiographically proved stenosis with the quantitative diminution
in radionuclide flow. Our visual analysis was considered too
insensitive for such a quantification and comparison.
In the Minneapolis VA Hospital, an Anger camera (PhoGamma III; Serle) was used with a low-energy, highsensitivity collimator and a 25% window centered over the
140 kev 99mTc photopeak. With the patient facing the
camera, 20 mCi of 99mTc-pertechnetate in less than 1 cc of
saline were injected as a bolus into an antecubital vein.
Serial 70-mm images of flow in the neck and head were obtained every three seconds following completion of injection.
Incapacitated patients were examined in the supine position.
Results
Subjects were divided into two groups: (1) 18 with unilateral ICA occlusion, and (2) 30 with unilateral or bilateral
ICA stenoses.
All ICA occlusions were situated at the carotid sinus or
close to its origin. In none of the 48 patients were there
significant lesions beyond the cervical carotid or within the
external carotid artery.
The results of the radionuclide flow study in these patients
with angiographically proved ICA lesions were tabulated
(table 2). Unilateral diminished radioactivity was observed
in 14 (78%) of the 18 subjects with ICA occlusion, 15 (50%)
of the 30 subjects with ICA stenosis, and 29 (60%) of the 48
subjects with ICA occlusion or stenosis.
Table 3 shows that the degree of ICA stenosis in the 30
subjects of Group 2 was severe in 13, moderate in 4, and
mild in 13. Diminished radionuclide flow was observed in
eight (62%) of the 13 subjects with severe stenosis, one (25%)
of the four subjects with moderate stenosis, and six (46%) of
the 13 subjects with mild stenosis.
The site of the diminished activity in the radionuclide examinations was correlated with the level of the ICA lesion
identified angiographically (table 4). Radioactivity was
diminished in the neck in 23 (80%) of the 29 patients with a
positive radionuclide study. In the other 20%, the diminished
activity was seen in the head in the region of the MCA. In 10
(71%) cases of ICA occlusion and 13 (87%) cases of ICA
stenosis, the diminished radioactivity was observed in the
neck.
The prevalence of bilateral ICA lesions proved angiographically was also assessed (table 5). In 26 (54%) of the 48
patients, bilateral ICA lesions were present. Ten (56%) of
42
STROKE
T.MII.K ".> Distribution of 4^ Cases of Aiu/ioi/raiihiealh/ Proved
Unilateral anil liilateral ICA Lemon
Type of ICA lesion
Occlusion
Stenosis
Total
Unilateral
S (44)*
14 (47)
22 (40)
Bilateral
10 C)6)
16 (:>:!)
IS
2 6 (.">4)
4S
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the 18 subjects with ICA occlusion and 16 (53%) of the 30
subjects with ICA stenosis had bilateral ICA lesions. The
distribution of the bilateral ICA abnormalities in both
groups was also tabulated (table 6). There were three
bilateral ICA occlusions which were excluded from this
study because of poor radionuclide flow study. It was
noticed that the radioactivity was always diminished on the
side of the occluded ICA irrespective of the severity of the
associated stenosis on the contralateral ICA. Diminished
flow was also on the same side as the stenosis if the stenosis
was unilateral (except for one patient with unilateral mild
stenosis and diminished flow on the opposite side). If the
ICA stenoses were bilateral, flow was always diminished on
the side with the greater stenosis. Six subjects were found
with mild bilateral ICA stenoses. Four of these had normal
radionuclide examinations. Two others had diminished flow
corresponding to the symptomatic side.
The abnormal radionuclide cerebral flow between unilateral and bilateral ICA lesions was also compared (table
7). The radionuclide study was abnormal in 16 (62%) of the
26 subjects with bilateral ICA lesions and normal in the
other ten subjects. In unilateral ICA lesions, 13 (60%) of 22
subjects had an abnormal radionuclide flow, the other nine
(40%) being normal. Therefore, the results of the radionuclide study were similar between unilateral and bilateral
ICA lesions.
Discussion
16
Bell noted 100% correlation between 99mTc CBF studies
and bilateral carotid angiograms in 13 cases with ICA occlusion. Jhingram et al.4 compared the contrast cerebral angiogram with the radionuclide angiogram. He found that in 24
subjects with angiographically proved unilateral carotid
occlusion, 23 had a positive radionuclide study. Jhingram
also found that if there was stenosis of the ICA, four of
seven subjects had a positive radionuclide study. Fischer et
al.5 noted that in 29 subjects with completed stroke, the cerebral angiogram corresponded with the radionuclide angiogram, but he did not mention the various types of carotid
artery lesions. Meschan et al.7 noted that in 11 of 15 subjects
with aortocranial atherosclerosis proved angiographically,
the dynamic flow on the brain scan was abnormal. In
Type of ICA lesion
Occlusion
Stenosis.
Total
of 2(1 Cases of Angiographicalh/
One side
Severity
Contralateral
Occlusion
Occlusion
Occlusion
Severe
Severe
Moderate
Mild
Severe
Moderate
Mild
Moderate
Mild
Mild
Mild
Proved
No.
4
:i
•i
1
6
•_>
6
26
1, JANUARY-FEBRUARY
1977
TAIU.K 7 Comparison of Hadioniiclide- CHF in '£2 Cases of
Unilateral and 2li Cases of liilateral ICA Lesion
Total
•Numbers in parenthese* arc percent.
TAWJK 6 Distribution
liilaleral ICA Lesion
VOL 8, No
'icV
lesion
Unilateral
Bilateral
Total
Isotope study
Normal
Al>n ormal*
Occlusi on
Stenosis
Occlusion
Stenosis
4
0
.">
10
4
10
13
J4
0
6
No.
22
26
4S
-•"Diminished radioisotope perfusion on one side.
another 39 subjects, the dynamic study was normal in 18.
Again, he failed to quantify or qualify the lesion in the aortocranial vessels. Griep et al.6 also noted that 11 of 14 subjects
with unilateral ICA occlusion had abnormal radioisotope
angiography. From the above studies, the correlation
between ICA occlusion and the results of radionuclide flow
examination is strong ranging from 79%" to 100%.16 In our
study, 78% or 14 of 18 subjects with unilateral ICA occlusion had a positive radionuclide study (table 2).
Few large studies in the English literature compare the
results of radionuclide angiography between patients with
various degrees of narrowing of the ICA lumen. Griep et al.6
noted a significant difference in the radionuclide angiograms between subjects with ICA occlusion and stenosis of
varying severity. Eleven of 14 of his subjects with unilateral
ICA occlusion, three of six subjects with 50% to 80%
stenosis and three of 29 subjects with ICA stenosis less than
50% had a positive study. In our study, while 78% or 14 of 18
subjects with unilateral ICA occlusion had a positive radionuclide study, it was observed only in 50% or 15 of 30
patients with unilateral or bilateral ICA stenoses. Thirteen
of these had severe stenoses, eight with positive radionuclide study. Of 13 subjects with mild ICA stenoses, six
had a positive radionuclide examination. The percent variation in positive flow between severe and mild stenoses is not
significant, 62% versus 46% (table 3). This contrasts with the
study of Griep et al. However, the system for grading ICA
stenoses in our study is different from Griep's and stenoses
less than 25% were excluded from our analysis. The following phenomena may account for the lack of discrepancy in
radionuclide angiograms between patients with high-grade
and low-grade stenoses.
(1) Our examination of the anterior flow images was
visual. Weissman et al.,21 by a quantitative analysis of the
slope of radioactivity with time over the entire cervical
region in dogs, found that surgically produced high-grade
stenosis and occlusion could be differentiated from controls.
Definitely, a quantitative analysis is superior to a visual
evaluation. With the improved technique of Weissman et al.,
probably the radionuclide flow in ICA stenosis can be quantified and severe ICA stenoses may be differentiated from
mild.
(2) Maynard et al." stated that occasionally it was apparent that decreased vascularity in an area during
radioisotope angiography was not due to decreased perfusion but to displacement of the.major blood vessel groups.
They added that perhaps with more attention to the
positioning of the patient and added experience, displacement of the vessels could be more easily detected. Probably
this is a factor accounting for the lack of difference in radionuclide flow in patients with severe and minor stenoses in
our study.
(3) The sensitivity of radionuclide angiography in detec-
RADIONUCLIDE CBF AND CAROTID ANGIOGRAM/Foo et al.
Downloaded from http://stroke.ahajournals.org/ by guest on June 16, 2017
tion of cerebral flow abnormalities remains unknown.
Strauss et al.20 has estimated that at peak activity of 10,000
counts per second in the head, at least a 10% to 20%
difference in flow is needed to be detected.
(4) We only assessed anterior flow images. While the
ICA, ACA and anterior MCA were easily identified,
vertebrobasilar and posterior MCA branches were less visible. Collateral flow, both intracranial and extracranial, is
frequent, especially in cerebrovascular atherosclerotic disease.22- " Developmental aortocranial vascular anomalies
also could give false results. A large vertebral artery also
may mimic the normal carotid artery.
Our sample size was not large. Further observation is required to compare the radionuclide flow between severe and
mild ICA stenosis.
While the incidence of positive radionuclide study is 78%
for ICA occlusion and 50% for ICA stenoses (table 2), the
average percent falls to 60%. Nevertheless, in the absence of
carotid angiography, an abnormal radionuclide flow cannot
predict whether the ICA is occluded or stenosed, although
the probability of finding an occlusion is higher.
No large studies in the English literature attempt to correlate the site of diminished radioactivity and the ICA
obstruction visualized angiographically. Fischer et al. s
observed that the radionuclide flow was diminished in the
MCA area in 27 cases of completed strokes, and in the area
of the ICA and MCA in another 13 cases, not including the
ones with "hemispheric retention." Their sample of cases
was not a homogenous one like the subjects in this study.
Rosenthall12 noted diminished flow in the MCA in a patient
with left ICA occlusion. Powell et al.17 also noted decreased
flow in the MCA in a case of proved left ICA occlusion. In
another case with right CCA ligation, the decreased flow
was seen in the neck. Rosenthall u stated that there was little
relationship between the site of obstruction and the
appearance of the isotope flow pattern in the positive study.
However, the relationship is significantly high in our subjects. In 80% of 29 angiographically demonstrated ICA
lesions, the diminished activity was seen in the neck in the
abnormal radionuclide studies (table 4). Therefore, in the
presence of diminished radioisotope activity in the neck, an
ICA lesion is more likely present than an MCA lesion.
Small vessel occlusions, developmental vascular anomalies
and collateral cerebral circulation may be present and, in
ICA disease with diminished isotope activity in the MCA
area, these factors may be partly responsible.
Angiographically or autopsy-demonstrated ICA lesions
are frequently bilateral. Bauer et al.18 found bilateral involvement in 72% of 172 patients with strokes studied angiographically. A little more than 50% of our subjects had
bilateral ICA disease (table 5). The radioisotope flow is
nearly always unsatisfactory in bilateral ICA occlusion.
Poor injection technique, increased intracranial pressure and
decreased cardiac output also give poor radionuclide study.
Probably, the radioisotope evaluation of bilateral ICA
occlusion can rarely be satisfactory. When the ICA lesion
was unilateral, diminished isotope activity was noted on the
involved side. With bilateral ICA lesions, excluding bilateral
ICA occlusion, a positive radionuclide study pointed to the
side of occlusion or greater stenosis. Our limited experience
with the two cases of bilaterally equally mild ICA stenosis
does not justify us to make a correlation between the radionuclide study and the svmDtomatic side if the stenosis nn
43
both sides is the same. Besides, the results of the radionuclide flow were similar in unilateral and bilateral ICA disease (table 7).
In summary, the radionuclide CBF examination plays a
role in the assessment of ICA lesions, but its limitations
have to be appreciated. Carotid occlusion or stenosis may be
clinically asymptomatic. Similarly, symptomatic stenoses
may not always be detected by the isotope method. The
presence of a unilaterally decreased flow in a patient with
clinically suspected ischemic stroke shows the side of ICA
disease if unilateral and the side of greater stenosis if the disease is present on both sides. Our study suggests that a
positive flow examination is more often found in occlusion
than stenosis and that diminished flow in the MCA area may
point to ICA disease. Bilateral cerebral contrast angiography is still mandatory for complete evaluation of the
degree of stenosis and presence of associated ulceration. The
data leading to the differentiation between major and minor
ICA stenosis are not sufficient to justify any conclusion.
Further observation is advisable and necessary.
References
1. Fisher CM: Occlusion of the carotid arteries. AMA Arch Neurol
Psychiat 65: 346-377, 1951
2. Fisher CM: Occlusion of the carotid arteries — further experiences.
AMA Arch Neurol Psychiat 72: 187-204, 1954
3. Toole JF, Janeway R: Diagnostic tests in cerebrovascular disease. In
Vinken PJ, Bruyn GW (eds): Handbook of Clinical Neurology, Vol 11.
Amsterdam, North Holland, pp 208-266, 1972
4. Jhingram SG, Johnson PC: Radionuclide angiography in the diagnosis of
cerebrovascular accident. J Nucl Med 14: 265-268 (May) 1973
5. Fischer RJ, Miale A Jr: Evaluation of cerebral vascular disease with
radionuclide angiography. Stroke 3 : 1-9 (Jan-Feb) 1972
6. Griep RJ, Wise G, Marty R: Detection of carotid artery obstruction by
intravenous radionuclide angiography. Radiology 97: 311-316 (Nov)
1970
7. Meschan I, Lytle WP, Maynard CD, et al: Statistical relationship of
brain scan, cervicocranial dynamic studies and cerebral angiography.
Radiology 100: 623-629 (Sep) 1970
8. Eklof B, Schwartz S: Critical stenosis of the carotid artery in the dog.
Scand J Clin Lab Invest 25: 349-353 (Jun) 1970
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Stroke. 1977;8:39-43
doi: 10.1161/01.STR.8.1.39
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