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229Discussion
Valdueza et al., Neurosonology and Neuroimaging of Stroke: A Comprehensive Reference, Second Edition (ISBN 978-3-13-141872-2), copyright © 2017 Thieme Medical Publishers
All rights reserved. Usage subject to terms and conditions of license.
What is the role of radiologic methods in the evaluation and grading of intracranial stenoses? For decades,
DSA has been the only method for direct imaging of the
intracranial circulation. However, until recently, no specifi c grading system has been established and stenoses
were usually estimated by “eyeballing.” DSA also has
technical shortcomings as it is commonly performed only
in two standard levels of projection (posteroanterior and
lateral). However, for MCA evaluation, the lateral image
does not allow suffi cient evaluation of either the distal
or proximal segments. In presumed mild to moderate
stenosis, oblique and rotated views would be required,
but these views are not part of the routine diagnostic
algorithm in a presumed stenosis. This may be one explanation for the “false-positive” MCA stenoses found in
TCD compared with DSA resulting in a low positive predictive value of only 36% in the SONIA trial (Feldmann et
al 2007). The second reason is the particular sensitivity
of ultrasound within the range of mild to moderate stenoses, as fl ow velocity is inversely related to the square of
vessel diameter. Exact quantifi cation of low-grade sten-
oses by DSA is diffi cult, not at least because of the small
vessel diameters—2–3 mm in their main stems. Also in
our case the right MCA and ACA stenoses would probably
have been missed if no special attention had been paid
because of the high-grade left-sided M1-MCA stenosis.
A systematic approach of using DSA for graduation
of stenoses >50% was fi rst adopted in the WASID study.
The stenoses were graded by using the residual and the
assumed normal vessel diameters. The latter was measured proximal to the stenosis within the widest visible
segment. If this was not available, the next normal distal
segment was used. If the complete M1-MCA or basilar artery was aff ected, the distal ICA or the dominant intrac-
ranial VA was used. For all intracranial ICA stenoses, the
petrosal ICA segment, or if also involved, the most distal
extracranial ICA diameter, were used as the reference. A
99% stenosis was diagnosed if a “gap sign,” defi ned as an
absent vessel signal over a short distance, was observed.
In an analysis of 24 aff ected intracranial arteries, the
inter-observer agreements for the three participating
readers ranged from 71% to 100% and the intra-observer agreements ranged from 83% to 100% (Samuels et al
2000). However, only conventional lateral and posteroanterior images were used and patients were included only
if a lumen reduction >50% was found on “eyeball” examination, so low-grade stenoses were not included.
TOF-MRA and contrast-enhanced MRA are now commonly used for assessment of the intracranial vasculature. TOF-MRA, based on the contrast mechanism known
as fl ow-related enhancement, accentuates hemodynamic
features and therefore generally overestimates the degree
of stenosis, especially in cases with low fl ow distal to the
ICAS. A short signal gap with preserved distal vessel segments, as in our patient, is not an occlusion but corresponds to a high-grade stenosis. In real occlusion, there
usually is a long signal gap with obviously reduced distal
vessel segments or total absence of signal (Aizawa et al
2012). In unclear cases it may be helpful to analyze the
source images which increase the sensitivity. Although
it is “old fashioned,” even the assessment of fl ow voids
on normal axial T2-weighted images may contribute
to the evaluation of vessel patency. Flow appearance in
the vessel segment distal to a stenosis allows assessing
its hemodynamic relevance. Reduced poststenotic vessel signal intensity indicates a hemodynamic relevant
stenosis and also the risk of recurrent stroke (Leng et al
2013, Liebeskind et al 2014). Brightness and visibility of
vessels on TOF-MRA are also related to hyperperfusion
in leptomeningeal collateral activation. A prominent PCA
sign in MCA steno-occlusive disorder means that the PCA
serves as a collateral vessel via leptomeningeal anastomoses (Uemura et al 2004). In acute MCA occlusion, a
prominent PCA signal was referred to as the “PCA laterality MRA sign” which indicated a better prognosis (Ichijo
et al 2013). Almost all MRA signs mentioned were also
present in our case. The mild stenoses of the right A1-ACA
and M1-MCA were visible as well as the poststenotic fl ow
distal to the left high-grade M1-MCA stenosis. Finally, the
collateral left-sided PCA fl ow was visible as a PCA signal
increase.
Contrast-enhanced MRA allows simultaneous imaging of the entire length of the brain-supplying arteries, from extracranial segments to distal intracranial
branches. It provides better morphologic visualization
than TOF-MRA and may therefore be used especially for
a high-degree stenosis with low fl ow. Its sensitivity to
detect intracranial lesions is lower than that of extracranial lesions (van Laar et al 2006b). In the near future,
3- and 7-T MRI scanners may further contribute to better characterization of intracranial stenoses with higher
accuracy and even the visualization of intracranial vessel wall abnormalities such as hematoma in dissection
or plaque morphology like intraplaque hemorrhage, lipid core, and fi brous cap in atherosclerosis (Bodle et al
2013, Majidi et al 2013).
Advanced multislice CTA provides excellent intracranial spatial resolution and fast data acquisition times
facilitating detection and graduation of intracranial stenoses. An issue of concern to be considered in this technique is radiation exposure and the intravenous contrast
required. However, in hyperacute acute stroke these
usually are not relevant contraindications (Klingebiel et
al 2002, Saba et al 2014). If fast acquisition is required,
no other technique apart from CT combines multimodal imaging (bone, parenchyma, perfusion) rapid data
acquisition (<10 seconds from aortic arch to vertex),
high spatial resolution, easy vital parameter monitoring,
operator independence, and high interrater agreement.
Newer techniques such as volume and dual-source CT
provide temporal information about blood fl ow and may
further increase the utility of the CT technique. Comparison of CTA and TOF-MRA for the detection of intracranial stenoses with DSA as reference method revealed a
higher sensitivity (98% versus 70%) and a higher positive
predictive value (93% versus 65%) for the CTA technique.
At least in selected constellations of distal BA near occlusion CTA was even superior to DSA, where DSA due
to low fl ow phenomena or retrograde BA fl ow suggested
total BA occlusion (Bash et al 2005).
The above developments require ultrasound to aim for
similar diagnostic reliability and anatomic distinctiveness, which can only be achieved using TCCS (rather than
TCD) in the hands of a well-trained sonographer, which
then does not compete with but rather complements the
results of other diagnostic modalities.
230
Valdueza et al., Neurosonology and Neuroimaging of Stroke: A Comprehensive Reference, Second Edition (ISBN 978-3-13-141872-2), copyright © 2017 Thieme Medical Publishers
All rights reserved. Usage subject to terms and conditions of license.
Case 6
Left P2 Posterior Cerebral Artery Stenosis
Clinical Presentation
A 25-year-old woman was admitted to a district general hospital with a disturbance aff ecting the right visual
fi elds of both eyes and a right-sided hemihypesthesia.
She had no history of migraine and had no other vascular risk factors other than using an estrogen-containing
contraceptive pill. No headaches were reported. Ischemic strokes of the left occipital lobe and the left thalamus were diagnosed on MRI. No magnetic resonance
angiography (MRA) was performed. Echocardiography,
electrocardiogram (ECG), and transcranial Doppler
(TCD) revealed normal fi ndings. Laboratory workup
demonstrated mildly raised levels of lipoprotein(a) and
slight hyperhomocysteinemia. Antiplatelet therapy with
aspirin was started. Four weeks later, the patient was
admitted to our Emergency Department because of a
subjective deterioration in her right-sided visual fi elds.
Initial Neuroradiologic Findings
MRI on the day of admission showed the known posterior cerebral artery (PCA) infarct in the left occipital region
in addition to a small area of ischemia of the left thalamus, identical to the initial fi nding 4 weeks previously.
T1-weighted images revealed a mild hyperintense signal
in the region of the cortical PCA infarction, indicating a
slight hemorrhagic transformation. Time-of-fl ight (TOF)
MRA was suggestive of an occlusion of the left distal
P2-PCA segment (Fig. B6.1 and Fig. B6.2).
Suspected Diagnosis
Hemorrhagic transformation of the known left-sided
PCA infarction.
Questions to Answer by Ultrasound
Techniques
• Was there an occlusion or stenosis within the left PCA?
• Was there evidence of vascular changes in the extracranial brain-supplying arteries, in particular within
the vertebrobasilar system?
Initial Neurosonologic Findings (Day 2)
Extracranial Duplex Sonography
Assessment of the carotid and vertebral arteries (VAs)
revealed normal fi ndings. There was no evidence of
a t h e r o s c l e r o s i s .
Transcranial Duplex Sonography
Normal and symmetric fl ow signals were seen in both
anterior cerebral arteries (ACAs) and middle cerebral
arteries (MCAs) (not shown). Flow velocities in both P1PCA segments and the right P2-PCA segment were within
the normal range. A distinct turbulent fl ow was evident
in the left distal P2-PCA segment. Doppler spectrum
analysis in this area revealed an increased fl ow velocity
(156/75 cm/s) (Fig. B6.3, Fig. B6.4, Fig. B6.5, Fig. B6.6; see
also Video
B6.1).
Conclusion
Distal left P2-PCA stenosis of unknown origin.
Clinical Course
On MRI there was no evidence of subsequent ischemic events. The mild hemorrhagic transformation in the
PCA infarct was considered to be the cause of the clinical
deterioration. Neurosonologic examination demonstrated a stenosis in the distal left P2-PCA segment, which
was probably overlooked during the initial TCD study
4 weeks previously. In light of the ultrasound fi ndings,
the small residual MRA vessel signal in the projection
of the left distal P2-PCA segment was thought to result
from the weak blood fl ow distal to a high-grade steno-
sis or to belong to the superior cerebellar artery. As the
only known potential vascular risk factors were a mildly
raised level of lipoprotein(a), a mild hyperhomocysteinemia, and the use of an estrogen-containing contraceptive
pill, an in-situ thrombus was suspected. Because of the
hyperhomocysteinemia the patient was prescribed folic
acid. Furthermore, we recommended that she stopped
taking the combined contraceptive pill. Aspirin therapy
for secondary stroke prevention was continued as no new
ischemic event had occurred. Repeated clinical and ultrasound follow-up over a 3-year period demonstrated a stable neurologic status and unchanged ultrasound fi ndings.
231Clinical Course
Valdueza et al., Neurosonology and Neuroimaging of Stroke: A Comprehensive Reference, Second Edition (ISBN 978-3-13-141872-2), copyright © 2017 Thieme Medical Publishers
All rights reserved. Usage subject to terms and conditions of license.
Fig. B6.1 Left: MR FLAIR image, axial plane. Hyperintense ischemic lesions in the left occipital lobe as well as in the left thalamus
(arrows). Right: T1-weighted image, axial plane. Mild hyperintense signals in the area of infarction, suggestive of hemorrhagic
t r a n s f o r m a t i o n ( a r r o w s ) .
P1-PCA-R
Fig. B6.3 TCCS ( tran stemp oral a ppro ach), r ight -side d inso nation,
midbrain plane. Normal fl ow in the right P1-PCA (fl ow velocity
79/37 cm/s).
P1 PCA-L
Fig. B6.2 3D TOF-MRA, axial maximal intensity projection (MIP).
Absent signal of the left distal P2-PCA main stem, suggesting highgrade stenosis or occlusion (large arrow). Note the weak vessel signal more distally (small arrows), probably corresponding to a PCA
branch or to the superior cerebellar artery.
P2-PCA-R
Fig. B6.4 TCCS ( tran stemp oral a ppro ach), r ight -side d inso nation,
midbrain plane. Normal fl ow in the right distal P2-PCA (fl ow veloc-
ity 78/43 cm/s).
P2-PCA-L
Fig. B6.5 TCCS ( transte mpor al a ppro ach), left -sided i nson ation ,
midbrain plane. Left P1-PCA shows a normal fl ow signal (fl ow
velocity 54/29 cm/s).
Fig. B6.6 TCCS ( tran stemp oral appro ach) , le ft-s ided inson atio n,
midbrain plane. Intrastenotic fl ow signal in the distal left P2-PCA
(fl ow velocity 156/75 cm/s).
232 Case 6 Left P2 Posterior Cerebral Artery Stenosis
Valdueza et al., Neurosonology and Neuroimaging of Stroke: A Comprehensive Reference, Second Edition (ISBN 978-3-13-141872-2), copyright © 2017 Thieme Medical Publishers
All rights reserved. Usage subject to terms and conditions of license.
Final Diagnosis
Left occipital PCA territory infarction with concomitant
thalamic involvement, probably caused by an in-situ
thrombus with residual left distal P2-PCA stenosis.
Discussion
Clinical Aspects
This patient is a 25-year-old woman with a left PCA infarction probably caused by a distal P2-PCA stenosis. In
view of the absence of the classic vascular risk factors, the
etiology of the stenosis remained unclear.
In the United States and Europe, 5–10% of stroke patients are less than 45 years of age (Jacobs et al 2002, Marini et al 2001). The incidence ranges from 11.3/100,000
per year in primarily white populations to 22.8/100,000
per year in black people (Kittner et al 1993, Kristensen
et al 1997). Young stroke patients more frequently have
cardiac embolism associated with a patent foramen
ovale (PFO). Also, a hypercoagulable state, illicit drug
use, and inherited blood clotting disorders are more
frequently found in young stroke patients than in the
older population (Pezzini et al 2003). One of the largest
population-based studies from 15 European stroke centers (the 15 Cities Young Stroke Study) reported ~3,331
patients aged 15 to 49 years with fi rst-ever ischemic
stroke. According to the TOAST criteria the cause of
stroke remained undetermined in 39.6% of cases, 17.3%
had a cardioembolism, 12.2% small-vessel disease, 9.3%
large-vessel disease, and 21.6% had another determined
etiology. PFO was the most frequent cardioembolic cause
with a proportion of 6.6% of all strokes in this series followed by cardiomyopathy (2.0%), PFO and atrial septal
aneurysm (1.8%), and ventricular wall hypo- or akinesia
(1.2%). In strokes of other determined etiologies, nonatherosclerotic noninfl ammatory and infl ammatory
arteriopathies, hematologic disorders, coagulopathies
(genetic, acquired, or related to systemic disorders), and
miscellaneous rare causes have to be mentioned. Cervical artery dissection was the most common cause with
12.8% of all strokes in the series, distantly followed by
antiphospholipid syndromes (1.2%), systemic vasculitis (0.8%), hematologic diseases (0.6%), systemic lupus
erythematosus (0.5%), primary angiitis of the CNS (0.5%),
migrainous infarction (0.4%), illicit drug use (0.4%), moyamoya (0.4%), pregnancy or puerperium-related (0.3%),
reversible cerebral vasoconstriction syndrome (0.2%),
fi bromuscular dysplasia (0.2%), hyperhomocysteinemia
or homocysteinuria (0.2%), CADASIL (0.2%), mitochondrial disease (0.2%), and other rare causes like HIV-related
vasculopathy in 0.1% (Putaala et al 2009, Yesilot Barlas et
al 2013). For further reading on moyamoya disease, see
Case 9); for cervical artery dissection, see Case 11 and
Case 19; for fi bromuscular dysplasia, see Case 13; for
migrainous infarction, see Case 22; for pregnancy-related
and reversible cerebral vasoconstriction syndrome, see
Case 36; and for HIV-related stroke, see Case 17.
CADASIL (cerebral autosomal dominant arteriopathy
with subcortical infarcts and leukoencephalopathy) is
a hereditary small-vessel disease without pronounced
ultrasound fi ndings but with a prolonged cerebral cir-
culation time (Chabriat et al 2009, Liebetrau et al 2002).
Fabr y’s disease, a lysosomal storage disease also rarely
related to stroke, was not specifi ed in the 15 Cities Young
Stroke Study. A separate large European multicenter trial
including 5,023 patients aged 18–55 years revealed defi -
nite and probable Fabry’s disease as main cause of stroke
in 0.5% and 0.4%, respectively (Rolfs et al 2013). Sickle cell
disease, also not specifi ed in the two European studies, is
discussed in Case 43.
In our patient none of the classic vascular risk factors
like arterial hypertension, diabetes mellitus, or hyperlipidemia were present and she did not smoke. However,
her homocysteine and lipoprotein(a) levels were mildly
raised and she was taking an estrogen-containing contraceptive pill. Metabolic disorders like hyperhomocysteinemia and homocystinuria are associated with ischemic
stroke in the young population (Mineyko and Kirton 2013,
Sébire et al 2004). The prevalence of mild or moderately
raised homocysteine levels ranges between 10% and 20%,
depending on the nutritional status of the studied population. Hyperhomocysteinemia is considered to be a risk
factor for the development of atherosclerotic vessel wall
changes in large arteries. A raised serum homocysteine
is further associated with a two- to threefold increased
risk of stroke (Bostom et al 1999, Giles et al 1998). Several
consecutive studies have demonstrated that homocysteine levels can be lowered by 10–15% if vitamin B and
folic acid supplements are taken. No benefi t of vitamin B
and folic acid treatment in stroke patients with raised
levels of homocysteine was reported, e.g., in the VISP
(Vitamin Intervention for Stroke Prevention) study (Toole
et al 2004). Also, a recent Cochrane review affi rmed that
lowering hyperhomocysteinemia will not decrease a patient’s cerebrovascular or cardiovascular risks for primary
or secondary prevention (Martí-Carvajal et al 2015).
Lipoprotein(a) as an independent risk factor for
stroke is also controversial. Some authors have reported higher mean lipoprotein(a) levels in stroke patients
compared with controls (Pedro-Botet et al 1992). A
prospective study demonstrated that the lipoprotein(a)
level is an independent predictor of stroke and vascular death (Ariyo et al 2003). A more recent study found
that raised lipoprotein(a) levels were associated with
a higher incidence of ischemic stroke. However, this
was true only for white women and nonwhites of both
sexes (Ohira et al 2006). Others saw increased values
related with an increased hereditary risk for suff ering
a vascular event. Its role as an independent stroke risk
factor remains unclear (Kamstrup et al 2009). Most investigations of vascular change in relation to lipoprotein(a) have focused on the extracranial arteries. Data
concerning intracranial atherosclerosis are scarce. One
study reported an association with the extent of intracranial atherosclerotic vessel wall changes (Arenillas
and Alvarez-Sabín 2005).
Female sex hormones used for contraception or for
postmenopausal hormone replacement therapy increase the risk for vascular events including stroke.
Since the fi rst reports of an association between oral
contraceptives and ischemic strokes (Vessey and Doll
233Discussion
Valdueza et al., Neurosonology and Neuroimaging of Stroke: A Comprehensive Reference, Second Edition (ISBN 978-3-13-141872-2), copyright © 2017 Thieme Medical Publishers
All rights reserved. Usage subject to terms and conditions of license.
1969), a large number of studies have addressed this
issue. In these studies, oral contraceptives were confi rmed to be an independent risk factor for stroke in
young women (Chan et al 2004, Gillum et al 2000, Petitti et al 1996, WHO 1996). However, this risk is low
and is probably further lowered by the current use of
low-dose estrogens and third-generation progestogens.
A review of progestogen-only oral contraceptives showed
no increased risk of stroke (Chakhtoura et al 2009). But
the risk can increase if other risk factors such as thrombophilia, age >30 years, smoking, hypertension, diabetes,
migraine, and obesity are additionally present.
The combination of the three mentioned and discussed risk factors in our patient might have contributed
to the development of an intracranial atherosclerotic lesion. However, as only one lesion was found, and because
of the young age of our patient, atherosclerosis seemed
unlikely and a local nonatherosclerotic vessel disease
more probable.
The frequency of PCA infarctions reported by most
stroke databases lies between 5% and 10% and is therefore lower than the incidence of MCA infarctions (Brandt
et al 2000). This may be one reason why there are only
a few large studies on PCA infarction and its etiology,
and modes of clinical presentation are less well analyzed. Few clinical studies with large number of patients
and detailed neurologic and cardiologic evaluation have
been published (Brandt et al 2000, Steinke et al 1997,
Yam am oto et a l 199 9) . In t hes e stud ies, em bol ic PCA i nfarctions occurred in 53–79% of cases. The majority of
embolic events were of cardiac origin (28–41%), and to a
lesser extent of artery-to-artery origin (22–32%). In-situ
thrombi were seen in 8–16% of cases. Rare causes, such
as coagulopathies, were found in 3–15% of cases while
the cause remained unclear in up to 24% of cases. A study
in a Korean population reported atherosclerotic macroangiopathy in 42.4% of 205 patients as the most frequent
cause of PCA stroke. Within this group, arterio- arterial
embolism was postulated in 47.5%, perforator artery
o c c l u s i o n i n 2 5 . 3 % , a n i n - s i t u t h r o m b o s i s i n 1 2 . 6 % , a n d
a combination of arterio-arterial embolism and perforator occlusion in 7.8%, respectively. Of the patients with a
macroangiopathic cause, a pathology limited to the PCA
alone was seen in 18.5%.The ventrolateral thalamus was
the most frequent infarct location, followed by occipital
lobe infarction in patients with isolated macroangiopathic PCA lesions (E. Lee et al 2009). The high rate of
involvement of the thalamus emphasizes that the occlusion of perforators at the level of the P1-PCA or proximal
P2-PCA segment is a relevant stroke mechanism. In cases of artery-to-artery emboli, atherosclerotic vessel wall
changes and dissections of the extracranial VA, followed
by the intracranial VA and the basilar artery (BA), have
been identifi ed as the most common embolic sources
(Yamamoto et al 1999). Occasionally, atherosclerotic
lesions of the internal carotid artery (ICA) can also cause
PCA infarction in those individuals with a fetal-type PCA
variant (Steinke et al 1997).
The high percentage of observed macroangiopathy
might have been caused by the higher prevalence of intracranial atherosclerosis in the Asian population as well
as by a better and more detailed vascular analysis of
the studied cases; however, the prevalence also seemed
r e m a r k a b l e i n a w h i t e p o p u l a t i o n . I n a D a n i s h T I A p o p u lation a PCA stenosis ≥50% according to the Baumgartner
criteria was found in 11% of all intracranial stenoses (von
Weitzel-Mudersbach et al 2012). An even higher prevalence of 30% was observed in an Italian study with TIA
and stroke patients (Viaro et al 2012).
Besides the rarer conditions such as hypercoagulopathies or Sneddon’s syndrome, migraine has repeatedly
been discussed as a potential cause of PCA ischemia.
A migraine-associated vasospasm with secondary development of thrombi has been discussed, and its proportion was estimated to be as high as 10% of all PCA
infarctions. One reason for this hypothesis is that PCA
infarctions are accompanied by headaches in up to 50%
of cases, unlike ischemic events in the anterior circulation (Brandt et al 2000, Pessin et al 1987). However, the
most favored hypothesis at present is that PCA infarctions may trigger a migraine in those who are currently
experiencing migraine attacks (Olesen et al 1993). Migraine as a basic underlying pathomechanism seems
unlikely and is not supported by the available pathoanatomic studies (Caplan 1991) (for further discussion on
migraine and stroke, see Case 22).
Angiologic and Anatomic Aspects
The PCA can be subdivided into four diff erent segments
from P1 to P4 (for further information, see Chapter 2,
“Posterior Cerebral Artery” under “Special Arterial Anatomy and Ultrasound Anatomy”). The pattern of PCA infarctions follows the anatomic paths of blood supply. The
P1-and proximal P2-PCA segments mainly supply the
paramedian midbrain and the medial and posterolateral
thalamus via small perforating arteries. Relevant cortical
PCA branches start in the midpart of the P2-PCA segment
with a highly variable anatomy. Usually the anterior temporal artery is the fi rst cortical branch followed by the
occipitotemporal artery mainly supplying the middle and
posterior parts of the basal temporal lobe. The following
P3-PCA segment starts in the quadrigeminal cistern and
quickly separates into the two main fi nal branches, the
parietooccipital and calcarine arteries, which supply the
mesial parietal and occipital cortex, respectively. Again,
variations of vessel courses and branching are more the
rule than the exception. Depending on the location of
occlusion or stenosis and the capacity to develop collateral pathways, typical infarcts and corresponding clinical
pictures appear. Embolic PCA occlusions may therefore
range from total PCA infarction to a circumscribed partial
cortical/subcortical ischemia. The latter frequently occurs
in the calcarine artery territory as emboli generally follow the most direct vessel pathways. Subsequently, visual
disturbance is the most common symptom, occurring
in up to 90% of cases. Involvement of the thalamus indicates involvement of perforating arteries. In our case an
involvement of the P1-PCA and/or proximal P2-PCA segment was assumed. However, the stenosis detected was
clearly distal to the origin of the thalamogeniculate or
thalamoperforating arteries which can best be explained
by a dynamic development of the vessel pathology. The
fi rst evaluation in our clinic was performed 4 weeks after
234 Case 6 Left P2 Posterior Cerebral Artery Stenosis
Valdueza et al., Neurosonology and Neuroimaging of Stroke: A Comprehensive Reference, Second Edition (ISBN 978-3-13-141872-2), copyright © 2017 Thieme Medical Publishers
All rights reserved. Usage subject to terms and conditions of license.
the initial ischemic event. Therefore, an initial proximal
occlusion, caused, for example, by an in-situ thrombus involving the perforator arteries, seems possible, followed
by secondary partial recanalization. The observed secondary hemorrhagic transformation is another positive
indicator of recanalization (Molina et al 2001) possibly
coinciding with the reported secondary deterioration of
the patient’s visual fi eld.
Ultrasound diagnostics of the posterior intracranial
circulation have considerably improved with the introduction of transcranial color-coded sonography (TCCS) in
the early 1990s. Unlike the TCD approach, this enables the
PCA, and in particular the P1-, P2-, and P3-PCA segments,
to be reliably identifi ed. In our case, an initial TCD exami-
nation in the fi rst admitting hospital was normal. We sus-
pect that the superior cerebellar artery (SCA) signal could
have been mistaken for the PCA as the two vessels are
closely related and fl ow velocities and fl ow profi les are
comparable (Pade et al 2010). However, even TCCS carries
the risk of such confusion because of the close vicinity
of both vessels (Baumgartner et al 1999). For further details on insonation of the SCA, see Chapter 2, “Superior
Cerebellar Artery” under “Special Arterial Anatomy and
Ultrasound Anatomy.”
Despite the described advantages of TCCS, not much
data exists on evaluation and quantifi cation of P2-PCA
stenoses. In analogy to their evaluation of MCA stenoses,
Baumgartner and coworkers (1999) described fl ow ve-
locity cut-off values for determination of ≥50% and <50%
P1- and P2-PCA stenoses. Compared with DSA results,
a systolic fl ow velocity ≥145 cm/s yielded a sensitivity,
specifi city, and positive and negative predictive values of
100%, 100%, 100%, and 91% for the detection of a ≥50%
PCA stenosis, respectively, and a systolic fl ow velocity
≥100 cm/s yielded values of 100%, 100%, 100%, and 100%
for the detection of a <50% PCA stenosis, respectively. Another study reported cut-off values of >200 cm/s
s y s t o l i c fl ow velocity for the detection of a P2-PCA
stenosis (Kimura et al 2000). However, the authors used
a n g l e - c o r r e c t e d v a l u e s i n a l l p a t i e n t s , i n c o n t r a s t w i t h t h e
former group, which might explain the apparent diff er-
ence between the two studies. An exact angle correction
in intracranial vessels is often diffi cult to obtain because
of the vessel elongations. Angle correction should therefore preferentially used in the midpart of a vessel segment within a straight vessel course of at least 10 mm. As
this is seldom the case within the proximal course of the
PCA, angle correction should not be attempted.
Scarce data are available comparing ultrasound
techniques and MRA or CT angiography (CTA) for evaluation of proximal PCA occlusions and stenoses. In
an Italian study of 292 symptomatic patients, a ≥50%
PCA stenosis (according to the Baumgartner criteria)
was confi rmed by a second modality in approximate-
ly 30% of patients with an intracranial stenosis at any
site (Viaro et al 2012). Similar high rates of ≥30% PCA
stenosis (26% and 25%, respectively) in symptomatic
patients were identifi ed by CTA (Homburg et al 2011,
Ovesen et al 2013). 3D TOF-MRA, however, is particularly prone to misinterpret low fl ow for occlusion, as
could be seen in our patient, who was initially wrongly
diagnosed as having a P2-PCA occlus ion.
Case 7
Valdueza et al., Neurosonology and Neuroimaging of Stroke: A Comprehensive Reference, Second Edition (ISBN 978-3-13-141872-2), copyright © 2017 Thieme Medical Publishers
All rights reserved. Usage subject to terms and conditions of license.
Cerebral Circulatory Arrest
235
Clinical Presentation
A 39-year-old woman presented with a 2-week history
of progressive headache. On admission to a district
general hospital, she complained of nausea, vomiting,
and vertigo. She had a past medical history of malignant melanoma—diagnosed 3 years prior to this presentation—and a cerebral metastasis had been surgically
removed from her right parietal lobe 1 year prior to admission. Her neurologic examination revealed absent
ankle jerks and bilateral positive Babinski signs. Cerebral MRI was unremarkable—specifi cally, there were no
signs of pathologic leptomeningeal enhancement. Two
days after admission, she became confused and aphasic
and was referred to the neurology department for further evaluation of either suspected tumor recurrence or
cerebral venous thrombosis.
Initial Neuroradiologic Findings
An unenhanced cranial CT on the day of transfer showed
right-sided brain swelling (Fig. B7.1). Cerebral venous
thrombosis was excluded by CT angiography (not shown).
Suspected Diagnosis
Impaired consciousness of unknown etiology.
Cerebral CT
A native cerebral CT scan showed generalized brain edema with small ventricles and loss of distinction between
the gray and white matter (Fig. B7.2 and Fig. B7.3A). Con-
trast-enhanced CT revealed a marked contrast fi lling of
the M1 middle cerebral artery (MCA) segment, the M2MCA, the A1 segment of the anterior cerebral artery (ACA)
and A2-ACA, and the P1 segment of the posterior cerebral
artery (PCA) and P2-PCA, indicating severely slowed cerebral perfusion (Fig. B7.2 and Fig. B7.3B).
Question to Answer by Ultrasound
Techniques
• Is there evidence of impaired perfusion of the brainsupplying arteries?
Initial Neurosonologic Findings
Extracranial Duplex Sonography
No vessel pathology was present. Doppler spectrum analysis of the extracranial brain-supplying arteries ~2 hours
after cerebral CT showed antegrade but severely reduced
fl ow velocities and increased pulsatility in all vessels (not
shown).
Clinical Course (1)
Meningoencephalitis or leptomeningeal carcinomatosis
was suspected, but studies of cerebrospinal fl uid (CSF) did
not show evidence of viral or bacterial infection. Cell differentiation was not possible due to bloody lumbar puncture. Paraneoplastic encephalitis was also considered, but
there was no evidence of this on the cerebral MRI performed in the district general hospital. An EEG revealed
generalized slowing of the background activity. During
the next 2 days, further signs of increased intracranial
pressure (ICP) became evident. Finally, she developed a
severe midbrain syndrome with coma and unreactive pupils requiring intubation and mechanical ventilation.
Transcranial Duplex Sonography
In all detectable intracranial vessels, a bidirectional
“ t o - a n d - f r o ” fl ow signal was observed (Figs. B7.4–B7.10).
Conclusion
Intracranial cerebral circulatory arrest.
Clinical Course (2)
A formal clinical diagnostic workup for the assessment of brain death was initiated (coma assessment,
testing of brainstem refl exes). However, the patient
died due to a sudden cardiac arrest before the planned
apnea testing was conducted. The underlying disease
236 Case 7 Cerebral Circulatory Arrest
Valdueza et al., Neurosonology and Neuroimaging of Stroke: A Comprehensive Reference, Second Edition (ISBN 978-3-13-141872-2), copyright © 2017 Thieme Medical Publishers
All rights reserved. Usage subject to terms and conditions of license.
Fig. B7.1 Unenhanced CT, axial plane: Initial CT with predominantly
right-sided mild brain swelling.
BA
Fig. B7.2 (A) Unenhanced CT, (B) postcontrast CT, corresponding
parietal axial planes: Follow-up CT after clinical worsening 2 days
later. Generalized brain edema with blurring of the gray–white
matter junction. Note small left hemispheric spots of contrast
appearing within the parenchyma: diff erential diagnosis residual
parenchymal fi lling or “stasis fi lling.”
BA
Fig. B7.3 (A) Unenhanced CT, (B) postcontrast CT, correspond-
ing basal axial planes: identical time point to Fig. B7.2. Generalized brain edema with blurring of gray–white matter junction at
the level of the skull base. Note the contrast fi lling of the M1-MCA,
M2-MCA, A1- and A2-ACA, and P1- and P2-PCA, indicating severely
slowed cerebral perfusion but, according to current guidelines, not
compatible with a CT-determined global cerebral circulator y arrest.
was unknown at this stage. Postmortem examination,
including neuropathologic autopsy, revealed generalized brain edema with signs of diff use leptomeninge-
al melanocytosis and multiple small areas of necrosis
throughout the brain.
Final Diagnosis
Generalized brain edema due to diff use leptomeningeal
melanocytosis resulting in elevated ICP, cerebral circulatory arrest, and subsequent cardiac arrest.
M1-MCA-R
Fig. B7.4 Tr an scr an ia l co lo r-c od ed d up le x so no gr aph y ( TCCS ; t ra ns temporal approach), right-sided insonation, midbrain plane: Right
M1-MCA with bidirectional fl ow signal (fl ow velocity 122/−24 cm/s).
Discussion
Clinical Aspects
In this case, a young woman died of complications from
leptomeningeal melanocytosis. These complications
arose from a generalized, malignant, cerebral edema-induced ICP elevation, which in turn, led to a cerebral circulatory arrest.
Leptomeningeal carcinomatosis (synonyms: neoplastic or carcinomatous meningitis, leptomeningeal metastases)—or in our case melanocytosis—is a condition
237Discussion
Valdueza et al., Neurosonology and Neuroimaging of Stroke: A Comprehensive Reference, Second Edition (ISBN 978-3-13-141872-2), copyright © 2017 Thieme Medical Publishers
All rights reserved. Usage subject to terms and conditions of license.
M1-MCA-L
Fig. B7.5 TCCS ( tran stemp oral a ppro ach), rig ht-side d inso nati on,
midbrain plane: Left M1-MCA (insonation depth: 86 mm) with a bidirectional fl ow signal (fl ow velocity −64/22 cm/s).
A1-ACA-L
A1-ACA-R
Fig. B7.6 TCCS ( tran stemp oral a ppro ach), rig ht-side d inso nati on,
midbrain plane: Right A1-ACA with bidirectional fl ow signal (fl ow
velocity −85/18 cm/s).
P1-PCA-R
Fig. B7.7 TCCS ( tran stemp oral a ppro ach), rig ht-side d inso nati on,
midbrain plane: Left A1-ACA (insonation depth 76 mm) with a bidirectional fl ow signal (fl ow velocity 58/−19 cm/s).
P1-PCA-L
Fig. B7.9 TCCS ( tran stemp oral a ppro ach), rig ht-side d inso nati on,
midbrain plane: Left P1-PCA (depth 78 mm) with a bidirectional
fl ow signal.
Fig. B7.8 TCCS ( tran stemp oral a ppro ach), rig ht-side d inso nati on,
midbrain plane: Right P1-PCA with bidirectional fl ow signal.
V4-VA-R
V4-VA-L
BA
Fig. B7.10 TCCS (transforaminal approach): Left and right V4 segment of the vertebral artery (VA) and basilar artery (BA) signal with
a bidirectional fl ow signal.
238 Case 7 Cerebral Circulatory Arrest
Valdueza et al., Neurosonology and Neuroimaging of Stroke: A Comprehensive Reference, Second Edition (ISBN 978-3-13-141872-2), copyright © 2017 Thieme Medical Publishers
All rights reserved. Usage subject to terms and conditions of license.
caused by diff use infi ltration of malignant cells from an
extrameningeal tumor. The incidence of leptomeningeal
metastases in solid tumors ranges between 4% and 15%.
Improvements in diagnostic and tumor treatment strategies have led to an increase in the reported incidence
of leptomeningeal metastases. Although all metastatic
tumors can potentially infi ltrate the meninges, this is
most frequently found in breast, pulmonary, and gastrointestinal cancers. Malignant melanoma can also lead to a
primary manifestation of meningeal infi ltration (Decha-
phunkul et al 2011), but it generally causes a secondary
leptomeningeal manifestation, which has been reported
to occur in some 22–46% of cases (de la Monte et al 1983,
Matsumura et al 2015).
Clinically, symptoms arise due to either (1) impaired
CSF circulation or (2) direct tumor infi ltration with
subsequent meningeal irritation. Symptoms usually
manifest asymmetrically, which refl ects the multifocal
character of the disease: 46% of patients initially present with gait disturbances and 70% have a complete loss
of refl exes. Epileptic seizures, cranial nerve palsies, and
radicular syndromes may also occur (Olson et al 1974,
Wasserstrom et al 1982). The main symptoms associated
with elevated ICP include headaches, nausea/vomiting,
and personality changes. Leptomeningeosis can also
imitate psychiatric disorders, thereby possibly complicating its diagnosis. Occasionally, the disease presents
as encephalitis—including a confusion syndrome, focal
neurologic defi cits, and seizures (Madow and Alpers
1951, Miller et al 1986).
The fi rst diagnostic procedures in suspected leptome-
ningeal carcinomatosis should be lumbar puncture and
CSF analysis. Results are frequently pathologic regardless
of the presence of pathologic cells, as (1) the CSF opening
pressure is elevated in >50% of cases, (2) total CSF protein
elevation is found in 80% of cases, and (3) a reduction in
glucose levels is found in 25–40% of cases (Posner 1995).
Less than 5% of patients have normal CSF fi ndings (Reuler
and Meier 1979). The diagnosis is confi rmed if malignant
cells are identifi ed. As only 40–50% of cases show patho-
logic cells in the initial CFS examination, repeated analysis is recommended with at least three lumbar punctures
on three consecutive days (Glass et al 1979).
Cerebral MRI is currently approved for diagnostic
morphology assessment. Gadolinium contrast-enhanced
T1-weighted images detect meningeal thickening and
enhancement with the highest sensitivity. However, the
rate of false-negative results is >30% (Yousem et al 1990).
Our patient did not show MRI meningeal enhancement, which is possible at an early stage, and her CSF
analysis was impaired due to repeatedly bloody lumbar
punctures. When other relevant diff erential diagnoses
have previously been excluded, a diagnostic meningeal
biopsy might be the only remaining confi rmatory test
for leptomeningeal carcinomatosis. For discussion of
further treatment options, see Chamberlain (2008) and
Pavlidis (2004).
Our patient fi nally developed a subsequent malignant
brain edema, elevated ICP, and a cerebral circulatory arrest,
which in combination with clinical testing (e.g., absence
of brainstem refl exes and presence of apnea) may lead to
total, irreversible loss of brain function—i.e., brain death.
Primary brain death, by defi nition, only occurs in patients
treated under intensive care conditions. Otherwise, brain
death is considered a sequela of cardiac death. Conversely, primary brain death leads to cardiac death and subsequent loss of blood circulation. Catecholamine treatment
and mechanical ventilation can stabilize a patient and
prevent cessation of systemic blood circulation despite a
total and irreversible loss of all brain function. Mollaret
and Goulon (1959) were the fi rst to describe a group of
comatose patients with loss of brainstem refl exes, apnea,
and lack of EEG activity. Causes that lead to irreversible
whole brain damage can either be of (1) primary origin
(intracranial hemorrhage, brain infection, trauma or diffuse meningeal tumor like in our patient) or (2) of secondary origin (cerebral hypoxia, e.g., related to temporary
loss of systemic blood circulation and successful cardiopulmonary resuscitation).
In most countries brain death is defi ned as the com-
plete and irreversible loss of all brain functions. To the
best of our knowledge, it is only in the UK that brain
death is defi ned as a loss of brainstem function (see
also Academy of the Medical Royal Colleges 2008, Smith
2015). Despite great cultural diff erences between coun-
tries, donation and transplantation of organs is widely
accepted and legalized by transplantation laws (Haupt
and Rudolf 1999, Wijdicks 2002, 2015). Although regional recommendations regarding brain death criteria
are heterogeneous, all guidelines maintain that the diagnosis should be clinically based. A certain number of
conditions and clinical signs have to be present—namely,
(1) the total loss of brain function should be determined
beyond doubt with a careful clinical examination; (2)
coma; and (3) loss of all brainstem refl exes (including
apnea) must be present. In most countries, two clinical
confi rmatory examinations within a time interval of
2–72 hours are required. In most U.S. states, one neurologic examination is suffi cient; however, some U.S.
state guidelines also require two examinations. Based
on all guidelines, other conditions (such as intoxication,
relaxation, hypothermia, metabolic or endocrine dysfunctions, and shock) that may cause the above clinical
fi ndings have to be excluded.
In Germany and Austria, two clinical examinations, or
one examination in combination with a technical investigation to confi rm the irreversibility in loss of brain func-
tion, can be performed. In the latter instance, the time
interval for brain death determination can be decreased.
Two main types of technical tests are available to prove
the irreversibility in loss of brain function: those which
document the loss of bioelectrical activity of the brain,
such as EEG, acoustically evoked potentials (AEP), somatosensory evoked potentials (SEP), and those which document complete cessation of cerebral perfusion such as
digital subtraction angiography (DSA), perfusion scintigraphy, ultrasound, or CT angiography (CTA). Because of its
simplicity and widespread availability, EEG is frequently
favored. In roughly 50% of European countries, evoked
brainstem potentials are approved diagnostic methods.
In the United States and Canada, EEG is the only electrophysiologic test that is approved. In the second group (assessment of cerebral perfusion), selective four-vessel DSA
is recognized to confi rm cerebral circulatory arrest. This
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