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156
Case 6
P2 Posterior Cerebral Artery Stenosis
Clinical Presentation
A 25-year-old woman was admitted to a district general
hospital with a visual disturbance affecting the right fields
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. An ischemic stroke of the left posterior cerebral artery (PCA) territory and the left thalamus was diagnosed on magnetic resonance imaging (MRI). No magnetic
resonance angiography (MRA) was performed. Echocardiography, electrocardiogram (ECG) and transcranial
Doppler (TCD) revealed normal findings. Laboratory
workup demonstrated mildly raised levels of lipoprotein(a) and slight homocysteinemia. Antiplatelet therapy
with aspirin was started. Four weeks later, the patient was
admitted to our emergency room because of a subjective
deterioration in her right-sided visual fields.
Initial Neuroradiologic Findings
MRI on the day of admission showed the known PCA
infarct in the left occipital region in addition to a small
area of ischemia of the left thalamus, identical to the initial
finding 4 weeks previously. T1-weighted images revealed
a mild hyperintense signal in the region of the corticalPCA
infarction, indicating a slight hemorrhagic transformation.
Time-of-flight (TOF) MRA was suggestive of an occlusion of
the left P2-PCA segment within the ambiens cistern
(Figs. B6.1, B6.2).
Suspected Diagnosis
Hemorrhagic transformation of the known left-sided PCA
infarction.
Questions to Answer by Ultrasound Techniques
• WasthereanocclusionorstenosiswithintheleftPCA?
• Was there evidence of vascular change in the extracra-
nial brain-supplying arteries, in particular within the
vertebrobasilar system?
Initial Neurosonologic Findings (Day 2)
Extracranial Duplex Sonography
Assessment of the carotid and vertebral arteries revealed
normal findings. There was no evidence of atherosclerosis.
Transcranial Duplex Sonography
Normal and symmetric flow signalswereseeninboth
anterior cerebral arteries (ACAs) and middle cerebral arteries (MCAs). In comparison with the right side, the left
P1-PCA segment showed a mild decrease in flow velocity
(systolic flow velocity: right: 79 cm/s; left: 54 cm/s). Distinct turbulent flow was evident in the distal left P2-PCA
segment. Doppler spectrum analysis in this area revealed
an increased flow velocity (flow velocity: 156/75 cm/s)
(Figs.B6.3–B6.6).
Conclusion
Distal left P2-PCA stenosis of unknown origin.
Clinical Course
On MRI there was no evidence of a further cerebral ischemic event. 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 findings, the small
residual MRA vessel signal in the projection of the left
distal P2-PCA segment was thought to result from the
weak poststenotic blood flow distal to a high-grade stenosis. 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 newischemicevent hadoccurred. Repeated clinical and
ultrasound follow-up over a 3-year period demonstrated a
stable neurologic status and unchanged ultrasound findings.
Final Diagnosis
Left PCA territory and thalamic infarction, probably caused
by an in-situ thrombus with residual left distal P2-PCA
stenosis.
Discussion
Clinical Aspects
Here, we discuss 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.
Discussion
In the United States and Europe, 5–10 % of stro ke pa tients are younger than 45 years (Jacobs et al. 2002, Marini
etal.2001).Youngstrokepatientsmorefrequentlyhave
cardiac embolism associated with a patent foramen ovale
as well as inherited blood clotting disorders than the older
population (Pezzini 2003). None of the above risk factors
were present in our patient. Furthermore, she had none of
the classic vascular risk factors of arterial hypertension,
diabetes mellitus, hyperlipidemia, and was a non-smoker.
However,her homocysteine and lipoprotein(a) levels were
mildly raised and she was taking an estrogen-containing
contraceptive pill.
The prevalence of mild or moderately raised homocysteine levels ranges between 10 % and 20 %, depending on
the nutritional status of the studied population. Hyper-
157
Degree of Neurosonologic Difficulty: Low
Fig. B6.1 MR FLAIR image, axial plane. Left: 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 transformation (arrows).
Fig. B6.3 TCCS (transtemporal approach), right-sided insonation,
midbrain plane. Normal flow in the right P1-PCA (flow velocity: 79/
37 cm/s).
Fig. B6.2 3D TOF MRA, axial MIP. Absent signal of the left distal P2PCA main stem, suggesting high-grade stenosis or occlusion (large
arrow). Note the weak vessel signal more distally (small arrows),
probably corresponding to a vessel branch.
Fig. B6.4 TCCS (transtemporal approach), right-sided insonation,
midbrain plane. Normal flow in the right P2-PCA (flow velocity: 78/
43 cm/s).
Case 6 P2 Posterior Cerebral Artery Stenosis
158
Degree of Neurosonologic Difficulty: Low
Fig. B6.5 TCCS (transtemporal approach), left-sided insonation,
midbrain plane. Left P1-PCA shows a normal flow signal (flow velocity: 54/29 cm/s).
homocysteinemia 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, Selhub et al. 1995). A
number of consecutive studies have demonstrated that
homocysteine levels can be lowered by 10–15% if vitamin
B and folic acid supplements are taken. However, the
studies so far have failed to demonstrate that this in turn
reduces the cerebro- or cardiovascular risk. This seems to
be true for primary as well as secondary prevention approaches. For example the VISP (Vitamin Intervention for
Stroke Prevention) study did not find a benefit of vitamin B
and folic acid treatment in stroke patients with raised
homocysteine levels (Toole et al. 2004).
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 lipoprotein(a) level is an independent
predictor of stroke and vascular death (Ariyo et al. 2003). A
more recent study has found that raised lipoprotein(a)
levels are associated with a higher incidence of ischemic
stroke. However, this was only true for white women and
non-Caucasians of both sexes (Ohira et al. 2006). 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-Sabin 2005).
Female sex hormones used for contraception or for
postmenopausal hormone replacement therapy increase
the risk for vascular events including stroke. Since the first
reports of an association between oral contraceptives and
ischemic strokes in 1969 (Vessey and Doll 1969), a large
number of studies have addressed this issue. In these
Fig. B6.6 TCCS (transtemporal approach), left-sided insonation,
midbrain plane. Intrastenotic flow signal in the distal left P2-PCA
(flow velocity: 156/75 cm/s).
studies, oral contraceptives were confirmed to be an independent risk factor for stroke in young women (Chan et
al. 2004, Gillum et al. 2000, Pettiti et al. 1996, World Health
Organization [WHO] 1996). However, this risk is low and is
probably further lowered by the current use of low-dose
estrogens and third-generation progestogens. The risk can
further increase if other risk factors such as thrombophilia,
age > 30 years, smoking, hypertension, diabetes, and obesity are present.
The combination of the three risk factors in our patient
(discussed above) might have contributed to the development of an intracranial atherosclerotic lesion. However, as
only one lesion was found, the actual etiology remains
unclear.
The frequency of PCA infarctions reported by most
strokedatabasesliesbetween5%and10%andistherefore
lower than the incidence of MCA infarctions (Brandt et al.
2000). This is why there areonly a few large studies on PCA
infarction and its etiology and modes of clinical presentation are less well analyzed. Three large clinical studies with
detailed neurologic and cardiologic evaluation of patients
have been published (Brandt et al. 2000, Steinke et al. 1997,
Yamamoto et al. 1999). In these studies, embolic PCA infarctions 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
thrombiwereseenin8–16 % of cases. Rare causes, such as
coagulopathies, were found in 3–15 % of cases while up to
24 % of cases, the cause remained unclear. Correspondingly, a pathoanatomic study reported an in-situ-thrombus in 10 % of cases with PCA occlusion while the proportion of assumed artery-to-artery embolic events was reported to be 50 % (Castaigne et al. 1973). The latter probably illustrates the limited opportunity for histopathologic
evaluation of cardiac embolic causes and a subsequent
shifting in favor of artery-to-artery emboli. In cases of
artery-to-artery emboli, atherosclerotic vessel wall
Discussion
159
changes and dissections of the extracranial vertebral artery (VA), followed by the intracranial VA and the basilar
artery (BA) have been identified as the most common
embolic sources (Yamamotoet 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).
Besides the rarer conditions such as hypercoagulopathies or Sneddon 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
has been estimated as higher as 10 % of PCA infarctions.
One of the reasons for this hypothesis is that PCA infarctions are accompanied by headaches in up to 50 % of cases,
in contrast with ischemic events in the anterior circulation
(Brandtetal.2000,Pessinetal.1987).However,themost
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, p. 269).
Angiologic and Anatomic Aspects
The PCA can be subdivided into four different segments
from P1 to P4 (for further information, see Chapter 2,
“Intracranial Arteries,” p. 24). The pattern of PCA infarctions follows the anatomic paths of blood supply. The P1and 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 middle of the P2-PCA segment with
the anterior temporal artery, followed by the occipitotemporal artery supplying the middle and posterior parts of
the basal temporal lobe. The subdivision of the latter, in the
posterior part of the ambient cistern, can be used to define
the end of the P2-PCA segment. The following P3-PCA
segment quickly separates into the two main final
branches, the parietooccipital and calcarine arteries,
which supply the mesial parietal and occipital cortex, respectively. 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 perforating arteries, as in our present
case, is suggestive of involvement of the P1-PCA or proximal P2-PCA segment. However, the stenosis detected in
our case was clearly distal to the origin of the thalamogeniculate arteries which indicates a dynamic development
of the vessel pathology. The first evaluation in our clinic
was performed 4 weeks after the initial ischemic event.
Therefore, an initial proximal occlusion, caused, for example, by an in-situ thrombus involving the thalamogeniculate 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’svisual
field. The unchanged stenosis over the observational period of 3 years is, however, uncommon for an embolic
event.
Ultrasound diagnostics of the posterior intracranial circulation have considerably improved with the introduction of transcranial color-coded sonography (TCCS) in the
early 1990s. Compared with the TCD approach, the PCA,
and in particular the P1-, P2-, and P3-PCA subsegments,
can reliably be identified. In our case, an initial TCD examination in the first admitting hospital was normal. We
suspect that the superior cerebellar artery (SCA) signal
could have been mistaken for the PCA, as both vessels
are closely related and flow velocities and flow profiles
are comparable (Pade et al. 2007b). However, the TCCS
techniquealsocarriestheriskofsuchconfusion(Baumgartner et al. 1999).
Despite the described TCCS advantages, only few data
exist on evaluation and quantification of P2-PCA stenoses.
In analogy to their evaluation of MCA stenoses, Baumgartner and coworkers (1999) described flow velocity cut-off
values for determination of ≥ 50 % and < 50 % P1- and P2PCA stenoses. Compared with DSA results, a systolic flow
velocity ≥ 145 cm/s yielded a sensitivity, specificity, and
positive and negative predictive values of 100 %, 100 %,
100 %, and 91 % for the detection of a ≥ 50 % PCA stenosis,
respectively, and a systolic flow velocity ≥ 10 0 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 systolic flow velocity for the
detection of a P2-PCA stenosis (Kimura et al. 2000). However, the authors used angle-corrected values in all patients, in contrast with the former group, which might
explain the apparent difference between the two studies.
As an exact angle correction in intracranial vessels is often
difficult to obtain because it requires visualization of a
straight vessel segment of at least 1.5–2cm (Giller 1994).
As thisis seldom the case within the proximal course of the
PCA we recommend in general to measure PCA velocities
without angle correction.
No systematic data are available comparing ultrasound
techniques and MRA or CTA for evaluation of proximal PCA
occlusions and stenoses. 3D TOF MRA is particularly prone
to misinterpret low flow for occlusion as could be seen in
our patient in whom distal P2-PCA occlusion was diagnosed.
Degree of Neurosonologic Difficulty: Low
160
Case 7
Cerebral Circulatory Arrest
Clinical Presentation
A 39-year-old woman presented with a 2-week history of
progressive headache. On the day of admission to a district
general hospital she complained of nausea, vomiting, and
vertigo. She gave a history of malignant melanoma, diagnosed 3 years prior to this presentation. One year before
presentation, a cerebral metastasis in the right parietal
lobe had been surgically removed.
Neurologic examination on admission revealed absent
ankle jerks and positive Babinski sign bilaterally. A cerebral magnetic resonance (MR) scan was unremarkable; in
particular there were no signs of pathologic leptomeningeal enhancement. Two days after admission the patient
became confused and aphasic and was referred to our
neurologic intensive care unit with a suspected diagnosis
of cerebral venous thrombosis (CVT).
Initial Neuroradiologic Findings
An unenhanced cranial computed tomography (CT) scan
on the day of transfer showed a mild right-sided brain
swelling (Fig. B7.1). CVT was excluded by computed tomographic angiography (CTA) (not shown).
Question to Answer by Ultrasound Techniques
• Was there evidence of impaired perfusion of the brainsupplying arteries?
Initial Neurosonologic Findings
Extracranial Duplex Sonography
Doppler spectrum analysis of the extracranial brain-supplying arteries showed orthograde but reduced flow velocities and increased pulsatility in all vessels.
Transcranial Duplex Sonography
In all detectable intracranial vessels a bidirectional “to-
and-fro” flow signal was observed (Figs. B7.2–B7.7). The
basilar artery (BA) could not be visualized.
Conclusion
Definite signs of cerebral circulatory arrest.
Suspected Diagnosis
Impaired consciousness of unknown etiology.
Clinical Course (1)
Meningoencephalitis or neoplastic meningitis was suspected, but cerebrospinal fluid (CSF) studies 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 electroencephalogram
(EEG) revealed generalized slowing of the background
EEG activity. During the next 2 days more signs of increased intracranial pressure (ICP) became evident. Finally, the patient developed a severe midbrain syndrome
with coma and nonreactive pupils requiring intubation
and artificial respiration.
Cerebral CT
A follow-up cerebral CT scan showed generalized brain
edema with small ventricles and loss of distinction between the gray and white matter (Fig. B7.8).
Clinical Course (2)
Ten hours after neurosonologic investigation the patient
died due to a cardiac arrest. The cause of death and the
underlying disease were unknown at this stage. Postmortem examination, including neuropathologic autopsy revealed generalized brain edema with signs of melanotic
leptomeningeal carcinomatosis and multiple small necroses in the whole brain.
Clinical Course (2)
161
Degree of Neurosonologic Difficulty: Low
Fig. B7.1 Unenhanced CT, axial plane. Initial CT with predominantly
right-sided mild brain swelling.
Fig. B7.3 TCCS (transtemporal approach), right-sided insonation,
midbrain plane. Left M1-MCA (insonation depth: 86 mm) with a
bidirectional flow signal (flow velocity: –64/22 cm/s).
Fig. B7.2 TCCS (transtemporal approach), right-sided insonation,
midbrain plane. Right M1-MCA with bidirectional flow signal (flow
velocity: 128/–24 cm/s).
Fig. B7.4 TCCS (transtemporal approach), right-sided insonation,
midbrain plane. Right A1-ACA with bi-directional flow signal (flow
velocity: –85/18 cm/s).
Fig. B7.5 TCCS (transtemporal approach), right-sided insonation,
midbrain plane. Left A1-ACA (insonation depth: 76mm) with a
bidirectional flow signal (flow velocity: 58/–19 cm/s).
Fig. B7.6 TCCS (transtemporal approach), right-sided insonation,
midbrain plane. Right P1-PCA with bidirectional flow signal.
Case 7 Cerebral Circulatory Arrest
162
Degree of Neurosonologic Difficulty: Low
Fig. B7.7 TCCS (transtemporal approach), right-sided insonation,
midbrain plane. Left P1-PCA (depth: 78 mm) with a bidirectional
flow signal.
Fig. B7.8 Unenhanced CT, axial plane. Follow-up CT taken 2 days
after admission to the neurologic intensive care unit showing generalized brain edema with blurring of the gray and white matter
junction.
Final Diagnosis
Generalized brain edema due to leptomeningeal carcinomatosis resulting in raised intracranial pressure, subsequent cerebral circulatory arrest, and brain death.
Discussion
Clinical Aspects
In the presented case, a young woman died from complications of leptomeningeal carcinomatosis. The underlying
mechanism was a generalized malignant brain edema that
ledtoincreasedICP,whichinturnresultedinacerebral
circulatory arrest.
Leptomeningeal carcinomatosis is a condition caused by
diffuse malignant cell infiltration from an extrameningeal
tumor. The incidence of leptomeningeal metastases in
solid tumors ranges between 4 % and 15 %. Because of
improvementsindiagnosticworkupsaswellasimproved
therapeutic strategies in tumor treatment, the reported
incidence of leptomeningeal metastases is rising. Any tumor causing metastases has the potential of meningeal
infiltration. Most frequently this is found in breast, pulmonary, and gastrointestinal cancers, as well as in malignant
melanoma. The latter causes a secondary meningeosis
carcinomatosisin 22–46% of cases (de laMonte et al.1983).
Clinically the patients become symptomatic because of
impaired CSF circulation or because of direct tumor infiltration and subsequent meningeal irritation. Frequently
the symptom manifestation is asymmetric, reflecting the
multifocal character of the disease, and About half of patients initially present with gait disturbances. Epileptic fits,
cranial nerve palsies, or radicular syndromes may also
occur (O lson et al. 1974, Wasse rstr om et al. 1982 ). In 70 %
of cases, there will be a complete loss of reflexes. In cases
with raised ICP, the main symptoms are headaches, nausea, vomiting, and personality changes. A meningeosis can
also imitate psychiatric disease, which might raise diagnostic difficulties. Occasionally the disease presents as
encephalitis, clinically including a psychosyndrome, focal
neurological deficits and seizures (Madow and Alpers
1951, Mil ler et al. 1986) .
The first diagnostic procedure in suspected leptomenin-
geal carcinomatosis should be lumbar puncture and CSF
analysis. Results are frequently pathologic regardless of
the presence of pathologic cells. The CSF opening pressure
is raised in more than 50% of cases. A raised total CSF
proteinisfoundin80%ofcasesandareductioninglucose
levels in 25–40 % of cases (Posner 1995). Only less than 5 %
of patients demonstrate completely normal CSF findings
(ReulerandMeier1979).Proofofthediagnosisisachieved
if malignant cells are documented. As only 40–50 % of
cases show pathologic cells in the initial CFS examination,
repeated analysis is recommended, with at least three
lumbar punctures on 3 consecutive days (Glass et al. 1979).
For morphologic examination, cerebral MRI is the cur-
rent approved diagnostic modality. Gadolinium-enhanced
T1-weighted images are most sensitive for the detection of
meningeal thickening and enhancement. However, the
rate of false-negative results is higher than 30 % (Yousem
et al. 1990). Our reported case did not show a meningeal
enhancement on MRI, and CSF analysis was impaired because of repeated sanguinary lumbar punctures. If other
relevant differential diagnoses are excluded, a diagnostic
meningeal biopsy might be the only option to confirm the
suspected diagnosis.
Our patient developed a subsequent malignant brain
edema, raised ICP, and a cerebral circulatory arrest, with
subsequent brain death. Brain death in most countries of
Discussion
163
the world is defined as the complete and irreversible loss
of all brain functions. To our knowledge, brain death is
definedasalossofbrainstemfunctiononlyintheUnited
Kingdom. Despite wide cultural differences between
countries, donation and transplantation of organs is
widely accepted and legalized by transplantation laws.
However, the regional recommendations for diagnosis of
braindeathasapreconditionfororgandonationareheterogeneous. All guidelines are common in that the diagnosis should be clinical. A certain number of conditions
and clinical signs have to be present. The total loss of brain
function should be determined beyond doubt with careful
clinical examination. Clinical signs are coma, loss of all
brain stem reflexes including apnea. In most countries,
two clinical confirmatory examinations with an interval
of 2–24 hours are required. At the same time, other conditions (such as intoxication, relaxation, hypothermia, and
metabolicor endocrinedysfunctions,as wellas shock)that
may cause the above clinical findings have to be excluded.
In Germany and Austria, two clinical examinations, or one
examination in combination with a technical investigation
to confirm the irreversibility in loss of brain function, are
performed. In the latter instance, the time interval for the
determination of brain death can be shortened and potential organ donation accelerated. Two main groups of technical tests are available: Those which document the loss of
bioelectrical activity of the brain and those which document complete cessation of cerebral perfusion. Because of
its simplicity and widespread availability, the EEG is frequently a favored technique. In about 50 % of European
countries, evoked brain stem potentials are approved diagnostic methods. In the second group, selective four-vessel digital subtraction angiography (DSA) is recognized to
prove cerebral circulatory arrest. This is accepted in all
countries which permit the use of technical confirmatory
testing. Todate, a neurosonologic examination is approved
for documentation of cerebral circulatory arrest only in
Germany. A recent survey in 226 neurologic and neurosurgical departments reported that 71 of them used ultrasound regularly as a confirmatory test. In Austria, a confirmatory DSA is required after neurosonologic examination (Wijdicks 2002).
In summary, there is widespread variation between
countries regarding the preconditions for clinical determination of brain death. Differences exist between concepts
of brain stem death (United Kingdom) and total brain
death (other European countries and North America) as
well as the approved technical confirmatory tests.
Angiologic and Anatomic Aspects
In a circulatory arrest, transcranial ultrasound is able to
depict the characteristic pathognomonic flow signals
which confirm the loss of brain perfusion. Three stages of
circulatory arrest can be distinguished:
1. The alternating flow, in which the sum of anterograde
and retrograde flow leads to a net zero flow which
correlates well with the circulatory arrest determined
by DSA.
2. Systolic spikes, defined as pure systolic flow of less than
200 ms duration and less than 50 cm/s peak systolic
flow velocity. In these cases it is thought that the retrograde flow component is either too slow to be depicted
or the integrated high-pass filters prevent their detection, therefore, filters should be set as low as possible.
3. Total absence of flow signals (Hassler et al. 1988).
The above three grades of cerebral circulatory arrest correlate well with the extracranial flow interruptions visible
inDSA(Hassleretal.1989).
Alternating flow signals in circulatory arrest can also be
seen in the extracranial part of the brain-supplying arteries. However, flow within the extracranial internal carotid artery (ICA) can be altered if blood flows via the
ophthalmic artery into the eye and face. In these cases a
dramatically reduced systolic flow and minimal diastolic
flow signal can be seen. The common carotid artery (CCA)
may show a small orthograde flow feeding the external
carotid artery (ECA) (Reutern von and Büdingenvon 1993).
A similar pattern may be observed in the extracranial
vertebral artery (VA) if residual flow occurs via small collaterals toward the neck muscles.
According to the recommendations of the Task Force
Group on cerebral death of the Neurosonology Research
Group of the World Federation of Neurology, a circulatory
arrest may be diagnosed by ultrasound if the following
criteria are fulfilled:
• A combined extracranial and intracranial ultrasound
analysis has to have been performed.
• The above described flow signalshave to be present over
a period of 30 minutes.
• Transcranially, all main stems of the brain-supplying
arteries have to be studied. At least two of them must
have the above-described alternating flow if the re-
maining vessel signals are missing (in Germany: all
main brain supplying arteries have to be visualized).
• The suspected diagnosis has then to be confirmed by
extracranial ultrasound analysis of flow in the CCA, ICA,
and VA (Ducrocq et al. 1998).
Transcranial ultrasound has been used for analysis of cerebral circulatory arrest in a number of studies. A recent
metaanalysis summarized data from 10 publications concerning the validity of the ultrasound method (Monteiro et
al.2006).Inaccordancewithdatafromthesubcommittee
of the American Academy of Neurology (Sloan et al. 2004)
it reported a sensitivity varying between 89 % and 95 % but
a specificity of only 99 %. The latter results from the following two cases:
• A 61-year-old woman with traumatic brain injury who
demonstrated oscillating flow patterns in both MCAs,
VAs, and the basilar artery (BA) with total absence of
brain stem reflexes but “weak respiratory movements”
during apnea testing (Hadani et al. 1999). A subsequent
Degree of Neurosonologic Difficulty: Low
Case 7 Cerebral Circulatory Arrest
164
perfusionsinglephotonemissioncomputedtomography (SPECT) scan was performed which demonstrated
absence of cerebral blood flow, and a follow-up apnea
test demonstrated apnea. However, the patient was hypothermic at the time point of ultrasound analysis,
whichshouldhavebeenanexclusioncriterion(see
clinical aspects).
• A 34-year-old man with traumatic brain injury who
fulfilled the clinical criteria of “brain stem death,” in
whom the authors found the typical transcranial Doppler (TCD) pattern of circulatory arrest while the EEG was
not yet isoelectric (Van Velthofen and Calliauw 1988).
Degree of Neurosonologic Difficulty: Low
However, the authors only presented a recording of a
singular vessel and did not comment if they found confirmatory signals in all brain supplying arteries. Also,
information about the time difference between ultrasound recording and EEG as well as results of a repeated
confirmatory TCD after 30 minutes was not available.
In both of these cases, the underlying pathology was incompatible with life and led to confirmed brain death
within a few hours. However, in our opinion the points
discussed cause doubt about the exact application of current guidelines for diagnosis of brain death, hence these
cases cannot be considered to be false positive. To our
knowledge, there is no report of a false positive TCD evaluation, resulting in a specificity of 100 %. However, if ultrasound is used to prove cerebral circulatory arrest, a number of further potential pitfalls that may lead to misinterpretation have to be considered.
A first potential pitfall is the quality of the bone window
used for insonation. In a prospective study the number of
patients with absent intracranial signals caused by a missing bone window was 7 %, however only 1.5 % of cases
demonstrated a complete absence of all intracranial vessel
signals (de Freitas and André 2006). These numbers are
low because the authors frequently used the transorbital
approach for analysis of the intracranial vessels. Therefore,
therecommendationshouldbetoeitherdocumentall
intracranial vessels with the required pathognomonic ultrasound signal or use the ultrasound method only, if a
recent previous ultrasound has been performed that permitted evaluation of the quality of the acoustic bone window.
Second, misinterpretation of ultrasound results may
arise from a persisting intracranial flow despite the presence of a clinical or EEG-confirmed brain death (false
negative result). Ogata et al. demonstrated that patients
with a complete loss of brain stem function may show a
persisting blood flow toward both cerebral hemispheres
(Ogata et al. 1988). In the above cited study by de Freitas
and André a persisting blood flow was found in 17.4 % of
cases that had diagnosed brain death on clinical criteria.
Patients with an open skull fracture, leading to a reduced
ICP might present with persisting cerebral flow despite the
total irreversible loss of brain function. Also the EEG might
show a persisting bioelectric activity, at least within the
first hours after clinical diagnosis of brain death (Van
Velthoven and Calliauw 1988). Such a false-negative result
may delay the diagnosis of brain death but a false-positive
would be unacceptable and must not occur.
Sofar,allreportedultrasoundstudiesondiagnosisof
cerebral circulatory arrest have used TCD. There are no
published data on the use of TCCS. Extracranial duplex
sonography has been used in one study that analyzed
theextracranialbloodvolumeflow.Atotalcerebralblood
volume flow below 100 mL/min, assessed as the sum of
volume flows in both ICA and VA was found in all patients
clinically diagnosed to be brain dead (see Chapter 3, “Parameters of Cerebral Hemodynamics,” p. 60, for volume
flow measurement). The authors suggested that this
method might be applied in cases with an absent transtemporal bone window (Schöningetal.2005).Afurther
advantage of the duplex sonographic approach is the simple differentiation between ICA and ECA, permitting a
clear attribution of alternating flow signals to the corresponding vessel. The detection of alternating flow in all
extracranial brain-supplying arteries excludes the presence of an intracranial orthograde flow, which would
also permit sonographic confirmation of cerebral circulatory arrest independent of the presence of a bone
window.
Case 8
Bilateral Intracranial V4 Vertebral Artery Stenosis
165
Clinical Presentation
A 56-year-old man was admitted to a general district
hospital with an apoplectiform left-sided hemiparesis,
double vision, and mild nausea. The symptoms resolved
except for an incomplete right oculomotor palsy. During
the following hours he experienced fluctuating neurologic
symptoms of transient left-sided hemiparesis, double vision, and reduced consciousness, each episode lasting for a
few minutes. He had no known vascular risk factors.
Initial Neuroradiologic Findings
Cranial computed tomography (CCT) showed normal findings without early signs of ischemic infarction. Yet, computed tomographic angiography (CTA) demonstrated a
distal basilar artery (BA) occlusion. Furthermore, severe
calcifications in the distal intracranial vertebral artery (VA)
on both sides were seen (not shown).
Suspected Diagnosis
Multiple transient ischemic attacks in the vertebrobasilar
artery territory due to distal BA occlusion of unknown
origin.
intraluminal stent was inserted (Fig. B8.2). The right VA
stenosis was left untreated.
Clinical Course (1)
The procedure was uneventful and subsequent blood pressure was kept within the high-normal range. The residual
neurologic symptoms resolved completely and no new
ischemic events occurred. Laboratory testing revealed elevated HbA
mellitus. One day after thrombolysis, a control CT scan was
performed which disclosed a small right cerebellar infarction within the superior cerebellar artery (SCA) territory
(Fig. B8.3). Secondary stroke prevention was started with
aspirin, and the asymptomatic patient was discharged.
Six weeks later the patient was admitted to our department for the first time with repetitive transient episodes of
vertigo, nausea, and gait disorder.
levels consistent with the diagnosis of diabetes
1
Question to Answer by Ultrasound Techniques
• Was there reocclusion of the BA after intraarterial
thrombolysis?
• What was the postinterventional status of the left VA
and of the known high-grade right distal VA stenosis?
Conventional Angiography (Day 1)
On the basis of the above findings, digital subtraction
angiography (DSA) was performed which confirmed the
occlusion of the BA beginning at the mid-basilar level.
Collateralization of the posterior circulation was seen
from the left internal carotid artery (ICA) via the left posterior communicating artery (PCoA). In addition, bilateral
high-grade stenosis of the distal VA was confirmed
(Fig. B8.1).
An artery-to-artery embolism originating from one of
the VA stenoses was considered to be the cause of the BA
occlusion. Six hours after the onset of symptoms an intraarterial thrombolysis via the left VA was performed—administration of 50 mg recombinant tissue plasminogen
activator (rt-PA) followed by 20 mg abciximab led to a
complete BA recanalization. Furthermore, dilatation of
the left high-grade VA stenosis was performed but no
Initial Neurosonologic Findings (Day 42)
Extracranial Duplex Sonography
B-mode sonography showed mild atherosclerotic vascular
changes in both carotid arteries without evidence of stenosis. Both V2-VA segment diameters were within the normal range (left: 4.5 mm; right: 3.2 mm). Doppler spectrum
analysis revealed an obviously increased pulsatility in the
leftV2-VAsegmentandonlymildsignsofincreasedpulsatility on the right V2-VA suggestive of distal flow obstruction (Figs. B8.4–B8.7).
Transcranial Duplex Sonography
A transtemporal insonation was impossible because of a
bilaterally absent temporal bone window. The transforaminal insonation showed turbulent flow signals and in-