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Special Arterial Anatomy and Ultrasound Anatomy 35
Fig. A2.55 TCCS, lower transforaminal insonation plane: Color-
mode imaging and Doppler spectrum analysis of both VAs. Top:
57/25 cm/s, Bottom: 46/16 cm/s.
Posterior Inferior Cerebellar Artery
Anatomic details: In 80–90 % of cases the PICA originates
in the mid-V4 segment, about 15mm proximal to the BA
confluens. In 10–20% of cases it arises from the proximal
BA. The PICA may also demonstrate considerable variations of length, caliber, and vessel course. There is unilateral aplasia in up to 10% of cases and hypoplasia in 5 %. It
has a mean diameter of 1.2mm, ranging from 0.3 mm to
1.9 mm.
Position and vessel identification: Because of frequently
observed large vessel loops, the PICA is detected mainly
with a flow signal toward, but also may be detected with a
flow signal away from the transducer. It may be found in a
lateral but also medial position from the V4-VA (Figs
A2.56, A2.57). Confident identification, however, may be
difficult and therefore cautious interpretation of findings
is recommended. Insonation rates of up to 50% have been
reported in a small series (Kaps et al 1992a).
Normal values: Flow velocities: see Ta b l e A2.7 (p. 52).
Basilar Artery
Anatomic details: The BA is a very constant vessel with a
mean length of 30 mm, ranging from 20 mm to 40 mm. Its
mean caliber is 3 mm, ranging from 2.5 mm to 3.5 mm.
With increasing age, elongated vessel courses can be observed (Fig.A2.7). In its proximal course it gives off the
paired anterior inferior cerebellar arteries (AICAs). The
paired superior cerebellar arteries (SCAs) originate from
the BA’s distal segment, just before the parting into the
two P1-PCA segments (Fig. A2.54). Rare anatomic BA variants are a hypoplastic proximal BA in cases with a persis-
Fig. A2.56 Left: CTA, 3D reconstruction (occipital skull removed),
image rotated 180° to correspond with the ultrasound image. Symmetric course of both V4-VA segments. Left-sided PICA originating
from the mid V4-VA segment with a straight course (arrows). Note
the tortuous course of the right-sided PICA (arrow). Right: TCCS,
upper transforaminal approach: Corresponding color-mode image
of the PICA arising laterally from the VA (arrows).
Fig. A2.57 TCCS, upper transforaminal insonation plane: Colormode imaging and Doppler spectrum analysis of the PICA with a
flow direction toward the transducer (flow velocity: 57/31 cm/s).
tent trigeminal artery, defined as a fetal connection between the C5-ICA segment and the upper third of the BA,
and a hypoplastic basilar top in cases with a bilateral fetaltypePCA(forfurtherdetailsseealso“Posterior Communicating Artery,” p. 39).
Proximal Basilar Artery
Position and vessel identification: The proximal BA is in-
sonated via the lower or upper axial transforaminal plane
demonstrating a flow direction away from the transducer
(for patient and transducer position see insonation of the
V4-VA segment, p. 34). The beginning of the BA is found at
a variable depth (frequently from 70 mm onward) that
depends on the vessel course and also on factors such as
neck circumference. It is easy to assess as long as both VAs
merge to form the BA in a typical manner. In cases of
2 Vascular Anatomy and Structure of Ultrasound Examination36
Fig. A2.58 MR T2-weighted images, sagittal plane. A BA with a
concave course into the interpeduncular cistern (common type).
B Straight BA course toward the suprasellar cistern (rare type). The
red dotted lines indicate the insonation plane, illustrating the problem of basilar top detection.
Fig. A2.59 MR T2-weighted image, coronal plane rotated 90 counterclockwise: BA segments which can be visualized by TCCS. Red box:
Visible BA segment via the transforaminal approach. Yellow box:
Visible BA segment via the transtemporal coronal approach.
elongated vessel courses or a hypoplastic VA terminating
as the PICA on one side the evaluation might be difficult.
For maximal signal yield from the distal BA segments the
probe can be pressed firmly onto the skin using the upper
transforaminal approach. The steeper the angle, the lower
the position of the probe in the neck should be (see
Fig. A2.52). Anteversion of the head facilitates distal insonation. With the transforaminal approach, the proximal
and middle segments of the BA can routinely be evaluated
within the prepontine cistern over a mean length of
10–20 mm. The location of its distal ending varies. In 61 %
of cases the distal segment of the BA rises posteriorly
following the course of the pons into the interpeduncular
cistern—leaving in the majority of cases the focus of insonation (Fig.A2.58). In these cases the distance between the
dorsumsellaeandthetipoftheBAismorethan0.5cm.
Successful insonation, however, may be possible if a large
transforaminal or an excellent transoccipital window is
present. In the remaining 39 % of subjects the distal BA
follows a more straight course, with the distance between
the dorsum sellae and superior BA bifurcation less than
0.5 cm (Huber 1982). However, even in these patients,
distal transforaminal BA insonation may be difficult as
has been shown by an elaborate study by Schulte-Altedorneburg et al., comparing duplex and anatomic data, confirm these findings. Via the transforaminal approach the
BA was visible with a mean length of 22 mm (range:
11–37 mm) while the mean anatomic length, assessed by
post-mortemexaminationwas33mm(range:25–
57 mm). The calculated missing length was approximately
12 mm, corresponding with the distal third of the vessel.
The distal BA segment with its parting into the PCA was
visible in 11 % of cases only (Schulte-Altedorneburg et al.
2000). The missing distal BA segment, however, may be
assessed via the transtemporal approach, provided that a
patent bone window is present (see also “Distal BA,” p. 37)
(Fig. A2.59).
Fig. A2.60 Right: anatomical preparation of the BA and its tributaries (adapted from Gänshirt 1972). Note the bilateral origin of the
AICA (red arrows). Left: TCCS, upper transforaminal approach: Corresponding color-mode image of the VAs merging to form the BA.
Note the two bilateral vessel signals with a flow direction toward the
probe representing both AICAs (white arrows).
Normal values: Flow velocities: see Ta b l e A2.7 (p. 52).
Anterior Inferior Cerebellar Artery
Anatomic details: The vessel originates in 75 % from the
proximalsegmentandin15%fromthemiddlesegmentof
the BA and is often much smaller than the PICA. However,
it may be a stronger vessel in cases of PICA aplasia or
hypoplasia. Duplication and triplication has been reported
in 20 % of each variant. Aplasia of the AICA is found in up to
2 % of cases. In general, the AICA presents a constant diameter of 1.0 ± 0.1 mm (Shrontz et al. 1986)
Position and vessel identification: Sometimes the vessel
can be identified via the transforaminal approach as a
bilateral arterial signal originating from the proximal BA
with a flow direction toward the transducer (Figs A2.60,
A2.61).
Normal values: No systematic values have been reported.
Special Arterial Anatomy and Ultrasound Anatomy 37
Fig. A2.61 TCCS, upper transforaminal insonation plane: Color-
mode imaging and Doppler spectrum analysis of an AICA with a
typical flow toward the probe (flow velocity: 53/23 cm/s).
Distal Basilar Artery
Position and vessel identification: Insonation of the distal
BA via the transforaminal approach is rarely possible, as
mentioned above. If there is no continuity of the BA signal
in color mode, distal signals observed in projection of the
BA might rather be from the PCoA or the ACA than the
distal BA. The distal BA can be confidently identified using
the transtemporal approach and the posterior coronal insonation plane. We recommend starting the insonation by
identification of the “carotid T junction” (C1-ICA, A1-ACA,
and M1-MCA) in the anterior coronal plane. From there the
transducer is pointed more posteriorly to identify the
“basilar-T junction” (distal BA, both P1-PCA) in a midline
position (distal BA, both P1-PCA) (Fig. A2.62). The hyperechogenic prepontine cistern and/or the sometimes observed hypoechogenic vascular sheath of the BA can be of
help for orientation. Because of the unfavorable insonation
angle, often near to 90°, exact flow velocity measurements
are impaired. However, the main question of distal BA
integrity can be dealt with by this approach. Using a combined transforaminal and transtemporal approach a BA
assessment over the total vessel length should be possible
(Pade et al. 2007a) (Figs A2.62, A2.63)
Normal values: Flow velocities: see Ta b l e A2.7 (p. 52).
Superior Cerebellar Artery (SCA)
Anatomic details: The bilateral SCA is a constantly developed vessel which over the first millimeters runs below
and parallel to the P1-PCA segments. It has a mean diameter of 1.3 mm (range: 0.8–2.3 mm) and is duplicated in up
to20%ofcases.In5%ofcasesitdoesnotrisefromthe
distal BA but from the P1-PCA segment.
Position and vessel identification: Because of its close spatial relation there is a high risk of mistaking the SCA for the
Fig. A2.62 A MR T2-weighted image, coronal plane, rotated 90°
counterclockwise: Yellow box indicating the vessel segments which
can be visualized by transtemporal TCCS. B, C TCC S, t ranstem pora l
insonation, coronal insonation plane: Color-mode imaging and
Doppler spectrum analysis of the distal BA. Note also both proximal
PCA segments.
Fig. A2.63 A MR T2-weighted image, coronal plane, image rotation
180°. The red box indicates the vessel segments which can be
visualized by transforaminal TCCS. B, C TCCS, upper transforaminal
insonation plane. Color-mode imaging and Doppler spectrum analysis of the midbasilar region (flow velocity: 73/31 cm/s).
proximal PCA segment during transtemporal insonation,
particularly when using the axial insonation plane. Also in
cases with P1-PCA hypoplasia the SCA might falsely be
identified as the proximal PCA segment. Best SCA identification can be obtained by transtemporal insonation in
the posterior coronal plane where it can be found parallel
to the PCA in up to 72 % of cases, provided that a good
temporal acoustic bone window is present (Fig. A2.64). A
further aid for differentiation is the visual stimulus paradigm. Opening of the eyes leads to a 21 % increase of flow
velocity in the PCA but only 5 % increase in flow in the SCA
(Pade et al. 2007b).
Normal values: Flow velocities: see Ta b l e A2.7 (p. 52).
2 Vascular Anatomy and Structure of Ultrasound Examination38
Fig. A2.64 Top left: MR T2-weighted image, coronal plane. Note the
flow void of the BA and its distal branching into the SCA (arrows) and
into the PCA (arrow). Top right: TCCS, transtemporal approach,
posterior coronal plane. Corresponding color-mode image of the
same patient demonstrating the signals from the distal BA, ipsi- and
contralateral SCA and ipsi- and contralateral PCA. Bottom left and
right: Color-mode imaging and Doppler spectrum analysis of the
PCA and SCA.
Posterior Cerebral Artery
Anatomic details: The PCA is subdivided into four vessel
segments (Figs A2.65, A2.66). The first, short P1 segment
extends from the vessel’s origin to the level of origin of the
PCoA, within the interpeduncular cistern. Normal variant
P1 segment has a mean caliber of 2.1mm (range
0.7–3 mm) and mean length 6 mm (range 3–9 mm). However, depending on the method of investigation(anatomic,
MRA, or ultrasound study) a fetal-type PCA is present in
about 10 to 15 % of subjects. In these cases the ICA provides
thebloodfortheposteriorcirculationviathePCoA
(Fig. A2.9). The P2 segment, which shows little variation,
begins after the origin of PCoA and runs within the ambient cistern. Its mean diameter is 2.3 mm (range
1.2–3 mm) and its mean length is 28 mm (range
15–46 mm). In the ultrasound-derived anatomic view, it
gives off two main branches, the anterior temporal artery
(ATA) and the occipitotemporal artery (OTA). The P3 segment starts at the point of origin of the OTA and bifurcates
within the quadrigeminal cistern or more distally into the
two main P4 segment branches, the parietooccipital artery
(POA)and the calcarine artery (CA). Often, the course of the
POA begins medially, and it crosses the CA in its course to
rise upward and laterally into the parietooccipital sulcus,
located between the thalamic and the cella media planes.
In contrast, the CA turns medially in plane of the midbrain,
into the interhemispheric space of the calcarine sulcus.
Fig. A2.65 Schematic drawing of the PCA segments (adapted from
Huber 1982), axial view. 1 = anterior temporal arter y; 2 = occipitotemporal artery; 3 = parietooccipital artery; 4 = calcarine artery.
Fig. A2.66 Schematic drawing of the PCA segments (adapted from
Huber 1982), sagittal view. 1 = anterior temporal artery; 2 = occipitotemporal artery; 3 = parietooccipital artery; 4 = calcarine artery.
Position and vessel identification: Early TCD studies divided the PCA into a “Doppler sonographic” P1 segment
with its flow direction toward the transducer and a “Doppler sonographic” P2 segment with a flow direction away
from the transducer. Real anatomy, however, is more complex. Now, TCCS permits analysis of flow signals of the PCA
in more detail. Without visualization of the PCoA the border between the P1 and P2 segments is not easy to define.
In all instances the P1-PCA segment is very short. The
following proximal third of the P2-PCA segment shows
similar to the P1-PCA segment, however, a flow toward
the probe.
Recently, we studied the distal course of the PCA in
subjects with a good temporal bone window. The first
relevant P2 branch, the ATA, can be visualized in the midbrain plane, at the turning point where flow direction
changes from “toward” to “away” from the transducer
(82 % of cases). Distally in the same plane a more prominent branch, the OTA can be detected (94 % of cases,
Fig. A2.67). The latter can be used to define the ending of
the P2 segment and the beginning of the P3 segment.
Following the P3 segment in the thalamic plane, the next
bifurcation which appears after a highly variable distance
determines the ending of the P3 segment. The more prominent branch usually represents the POA (46 % of cases).
The second branch is the CA (which was visible in 24 % of
our cases, Fig. A2.68). The latter vessel follows a basal and
then medial course and demonstrates a prominent re-
Special Arterial Anatomy and Ultrasound Anatomy 39
Fig. A2.67 TCCS, transtemporal insonation, upper pontine to
midbrain plane. Right: Color-modeimagingoftheproximalPCA.
A Proximal P2-PCA. B Anterior temporal artery. C Distal P2-PCA.
D Occipitotemporal artery. Left: Doppler spectrum analysis of vessel
segments in A–D : A 60/31 cm/s, B 36/16 cm/s, C 57/29cm/s,
D 49/20 cm/s.
0–20 years 21–50 years 51–74 years
Normal 100 93 35
Tortuous 0765
sponse to visual stimuli (flow velocity increase > 50 %),
which may help to differentiate the CA from the POA
(Schreiber et al. 2007).
Fig. A2.68 TCCS, transtemporal insonation, midbrain to thalamic
plane. Left: Color-mode imaging of the distal PCA. A P3-PCA. B Calcarine artery. C Parietooccipital artery. D Basal vein of Rosenthal.
Left: Doppler spectrum analysis of vessel segments in A–D: A 47/
24 cm/s, B 30/14 cm/s, C 35/23 cm/s, D 12/9 cm/s.
BA. Such a “complete” FT-PCA however, is rare, as postmortem analysis mostly reveals the existence of a small
vessel bridge, i. e., a hypoplastic P1 segment (Saeki et al.
1977). This variant, which can today often be depicted by
Normal values: Flow velocities: see Ta b l e A2.7 (p. 52).
neuroimaging techniques should then be called a partial
FT-PCA. However, the criteria for differentiating between
Posterior Communicating Artery
Anatomic details: The PCoA connects the anterior and the
posterior circulation. Posteriorly it inserts between the P1
and the P2 segment. If the vessel is normally developed, it
has a mean length of 14mm (range 12–17mm), a mean
caliber of 1.2 mm (range 0.5–3.3 mm) and follows a
straight or a tortuous course (Tab l e A 2 . 5), the latter being
more frequent in the older population. An important variant is the fetal-type PCA (FT-PCA) in which the PCA directly originates from the ICA without connection to the
partial FT-PCA and a strong PCoA are inconsistent. For
instance, from a morphologic point of view a FT-PCA can
be assumed to present if the PCoA diameter equals the
diameter of the other basal cerebral arteries. If a PCoA
diameter of > 2 mm is used as a cut-off value, FT-PCA can
be found in 12% of hemispheres (Lang 2001). A more
pragmatic approach is to define an FT-PCA whenever the
PCoA diameter exceeds the P1 diameter, which has been
found in 22 % of hemispheres (Lang 2001). Saeki and coworkers (1977) reported similar findings of 20 % unilateral
and 2 % bilateral FT-PCA. Other published anatomic data
Tab l e A2 .5 Anatomical variants of the PCoAin
relation to age (%) (adapted from Huber 1982)
2 Vascular Anatomy and Structure of Ultrasound Examination40
Fig. A2.69 TCCS, transtemporal approach, axial midbrain plane:
Circle of Willis with a good color-mode signal of the PCoA.
from the ICA to the PCA (Hoksbergen et al. 2000b). Vessel
identification might, however, be impaired due to a low
net flow or an elongated vessel course (Fig. A2.69). In our
experience the latter can lead to a bidirectional flow in the
PCoA which may partly explain the discrepant published
findings of its flow direction. In the FT-PCA variant the
PCoA is often a strong vessel frequently visible on colormode TCCS. Applying the CCA compression test, Hoksbergen and coworkers (2000b) found an FT-PCA—defined as
reduction or cessation of flow in the PCoA—in 6.5 % of
hemispheres and 13 % of cases. However, this test can not
be recommended as a routine procedure—both because of
the inconvenience for the patient caused by the applied
supraclavicular pressure and because of the 0.4% risk of
triggering a transient ischemic attack (TIA) (Jatuzis et al.
2000) or in singular cases even a manifest ischemic stroke
(Khaffaf et al. 1994). Instead we suggest the use of oscillation tests for analysis of PCA blood supply. Similar to the
oscillation test for ECA/ICA differentiation, the effects of
ipsilateral submandibular extracranial ICA oscillation and
extracranial V3-VA oscillation of the dominant VA onto the
P2- or P3-PCA profile can be analyzed. A stronger effect on
ICA oscillation favors the diagnosis of a FT-PCA and a
stronger effect on VA oscillation favors regular-type PCA
(Fig. A2.70). Applying this technique, a 17 % FT-PCA prevalence has been found which is in good agreement with
the results of the published CCA compression test data
(Siemieniec et al. 2006) (for further information, see Chapter 5, “Intracranial Collateral Pathways,” p.101).
Fig. A2.70 Ultrasound determination of fetal-type PCA variant. Left
column: Top: Oscillation of the submandibular ICA; middle: Marked
oscillation effect in the P2-PCA induced by right IC A oscillation; and
bottom: Mild oscillation effect in the P2-PCA during left ICA oscillation. Middle column: Top: Oscillation of the V3-VA atthe atlas loop;
middle and bottom: No effect and mild oscillation effect in the P2PCA during left and right V3-VA oscillation, respectively. Right column: Top: TOF MRA, 3D-reconstruction: Note the strong PCoA
(arrow) and the absence of the P1-PCA; bottom: TCCS, transtemporal approach, axial upper pontineinsonation plane: Corresponding
color-mode image. Note the strong PCoA signal (arrow).
vary between 15% and 36 % (see overview in van Raamt et
al. 2006).
Position and vessel identification: The PCoA is insonated
via the transtemporal approach usually between the axial
upper pontine and midbrain plane (Figs A2.29, A2.30).
Under physiological circumstances and in young subjects
(mean age of 38 years) a PCoA flow can be observed
unilaterally in 70% and bilaterally in 30 % with a flow
directiontowardtheICAinabout75%ofcases(Klötzsch
et al. 1996). In an older population (mean age of 61 years)
only 13 % of vessels were detected in all cases with a flow
Normal values: Flow velocities: see Ta b l e A2.7 (p. 52).
General Venous Anatomy
For many years, ultrasound studies of the brain-supplying
arteries have almost exclusively been the focus of scientific
research and clinical application. Underlying reasons for
the “neglect” of the venous part of cerebral circulation
have been the lower absolute numbers of solely venous
diseases, the assumed greater anatomic variability of veins
and sinuses, and technical limitations of analysis of “lowflow” vessels. However, the intracranial venous circulation, assumed to be 60–70 % of the global cerebral blood
volume, does have an important role in the equilibrium of
cerebral perfusion and is—besides cerebral sinus and venous thrombosis—involved in a variety of primarily nonvenous pathologies, e. g., AVMs and dural fistulas. In contrast to the arteries with their “windkessel” function, the
intracranial veins and sinuses are pure blood flow conductors. Two more important differences from the general
venous system should be mentioned here. First, intracranial venous vessels do not collapse, even if the transmural
pressure is zero. Second, there is complete absence of any
venous valves up to the level of the internal jugular veins,
permitting free blood flow in any direction depending on
need.
General Venous Anatomy 41
Fig. A2.71 Schematic drawing of the cere-
bral venous system. 1 = sylvian vein (superficial middle cerebral vein); 2 = vein of Trolard (postcentral vein); 3 = vein of Labbé;
4 = Rolandic vein (central vein) 5: anterior
cerebral vein; 6= deep middle cerebral vein;
7 = basal vein of Rosenthal; 8 = internal cerebral vein; 9 = vein of Galen. Venous vessel
segments accessible with duplex sonography areshown in blue. (Adapted from Feneis
1970.)
Fig. A2.72 Schematic drawing of the cerebral venous system. 1 = superior sagittal sinus; 2 = inferior sagittal sinus; 3 = internal
cerebral vein; 4 = vein of Galen; 5 = straight
sinus; 6 = confluence of sinuses; 7 = transverse sinus; 8 = basal vein of Rosenthal;
9 = sigmoid sinus; 10 = internal jugular vein,
11 = basilar plexus; 12 = inferior petrosal
sinus; 13 = cavernous sinus; 14 = pterygoid
plexus; 15 = sphenoparietal sinus;
16 = superior petrosal sinus. Venous vessel
segments accessible with duplex sonography areshown in blue. (Adapted from Feneis
1970 and Huber 1982.)
Intracranial Venous Anatomy
The intracranial veins can be divided into a superficial
venous system draining the blood from the hemispheres
and a deep venous system collecting blood from the thalamus, white matter, and basal ganglia. The superficial
veins over both hemispheres connect to a vascular network which can be classified, according to the common
flow direction, into ascending and descending veins. The
ascending veins take the blood via 10–12 bridging veins
into the superior sagittal sinus (SSS). The most prominent
of these veins is the vein of Trolard, located in the postcentral region. The most prominent descendingsuperficial
veins are the vein of Labbé, draining into the transverse
sinus (TS), and the sylvian vein, also called superficial
middle cerebral vein, predominantly draining into the
sphenoparietal sinus (SpPS) (Fig. A2.71,left).
The main deep cerebral veins are the paired basal veins
of Rosenthal (BVR) collecting blood from both anterior
cerebral veins (ACVs) and both deep middle cerebral veins
(DMCVs), the internal cerebral veins (ICVs) with their tributaries, the thalamostriatal veins and septal veins of the
cavum septum pellucidi. The BVR and ICV flow into the
unpaired vein of Galen (VG) which along with the inferior
sagittal sinus (ISS) merge to form the straight sinus (StS)
(Fig. A2.71,rightandFig. A2.72).
The venous sinuses are the final recipients of the blood.
In contrast with the other intracranial veins they cannot
change their diameter as they are surrounded by an inflexible dural sheath. The StS and SSS merge occipitally at
the confluence of sinuses (CoS) and split into the paired
transverse sinuses which then take the blood via the sigmoid sinus (SiS) into the internal jugular veins (IJV). Besides the confluence of sinuses (CoS) the paired cavernous
sinus (CS) is another major blood collecting and distribut-
2 Vascular Anatomy and Structure of Ultrasound Examination42
ing venous segment. It collects blood from the orbit and
from the sylvian veins mainly via the SpPS. From there the
blood can be distributed via the inferior petrosal sinus
(IPS)orsuperiorpetrosalsinus(SPS)intotheIJVsoralternatively via the emissaries of the skull base into the pterygoid plexus (Fig. A2.72).
Extracranial Venous Anatomy
For a long time the paired IJVs were thought to be the main
cerebral drainage pathways, collecting the blood via the
superior jugular bulb from the SiS and the IPS (Fig. A2.73).
However, recent studies have shown that the jugular
drainage strongly depends on the body position. In the
supine position the main drainage in most individuals indeed follows the IJVs. However, changing to an upright
position leads to a dramatic reduction and frequently even
complete cessation of jugular blood flow (Valdueza et al.
2000).Atthesametimeanincreaseinbloodflowcanbe
detected in the vertebral venous system (Fig. A2.74),
which is frequently neglected in general anatomy. It consists of a complex vessel configuration with several longitudinal valveless channels, connected via multiple segmental anastomoses. It can be divided into the anterior
and posterior intraspinal segments and the anterior and
posterior extraspinal segments. The anterior intraspinal
segment probably has the greatest drainage capacity. It
lies within the epidural fatty tissue and its veins have a
diameter up to several millimeters (Eckenhoff 1971). It
receives blood at the craniocervical junction in a complex
manner via the anterior, lateral and posterior condylar
veins which themselves receive blood via the condylar
confluence from the IPS, superior jugular bulb and the
basilar plexus (San Millan Ruiz et al. 2002). The posterior
intraspinal segment is usually small, not well developed
and receives blood from the confluence of sinuses via the
Fig. A2.73 Schematic drawing of the jugular drainage system (Right: adapted from
Schünke et al. 2006): 1 = superior sagittal
sinus; 2 = confluence of sinuses; 3 = sigmoid
sinus; 4 = superior bulb of the internal
jugular vein; 5 = pterygoid plexus; 6 = suboccipital plexus; 7 = internal jugular vein;
8 = vertebral vein; 9 = deep cervical vein;
10 =valves of theinferior bulbof the internal
jugular vein, 11 = anterior intraspinal
segment of the vertebral venous system;
12 = subclavian vein.
Fig. A2.74 Schematic drawing of the vertebral venous system. Left: The ramified
intraspinal segment of the vertebral venous
system is nicely demonstrated in this historical picture (adapted from Bock 1823).
Right: Schematic drawing of the cervical
spine (brown), cervical myelon and roots
(yellow), transverse plane: Vertebral venous
system. 1 = anterior intraspinal segment;
2 = posterior intraspinal segment; 3 = vertebral vein as part of the posterior extraspinal segment; 4 = anterior extraspinal
segment; 5 = transverse run of a spinal vein
communicating between the extraspinal
and intraspinal veins.
Special Venous Anatomy and Ultrasound Anatomy 43
occipital sinus. The anterior extraspinal segment is probably of little significance. It is connected to the CS via the
pterygoid plexus and the pharyngeal plexus. More important is the posterior spinal segment which consists of the
vertebral veins (VVs) and the deep cervical vein(s). The
former develop from the suboccipital venous plexus, in
great part surrounding the VAs, and run parallel as single
or doubled vessels to the VAsthrough the transverse processes of the cervical vertebra. Like a rope-ladder, they are
in multiple segments, connected to the anterior intraspinal segment via the neural foramina. The deep cervical
vein receivesblood from the SiS viathe mastoidal emissary
andrunsasasingularvesselorinformofmultiplevessels
in between the posterior muscles of the neck. It may also
connect via segmental anastomoses to the VVs. The VVs
and deep cervical vein frequently drain into the subclavian
vein. However, they may also merge into the IJV before
draining into the brachiocephalic and superior caval vein.
General Structure of Venous Ultrasound Examination
For insonation of the cerebral veins, like for the insonation
of the arteries supplying the brain, the patient should lie in
a comfortable supine position. In general, the access paths
and transducers used are also identical. However, the system settings including filters and the PRF has to be adjusted for the analysis of low-velocity signals, i. e., filters
have to be switched off and the PRF must be reduced.
Extracranially, the patient’s head needs to be in a straight
position to avoid flow alterations caused by unilateral or
bilateral venous outflow obstruction. Also, care must be
taken to not compress, e. g., the IJV when the transducer is
applied to the skin of the neck if reliable velocity measurements areto be taken.Because of thestrong dependency of
venous outflow on body position, the patient should preferably be studied in a completely supine position and if
possible without elevating the head. Similar to arterial
insonation, we recommend usually using angle-corrected
measurements for extracranial and nonangle-corrected
measurements for intracranial measurements.
reference data of reported normal values for flow velocities are given in Tab l e A 2.8 (p. 53). For all relevant veins
and sinuses video examples are included in the accompanying DVD.
Intracranial Veins and Sinuses
Similar to the examination of intracranial arteries a sector
transducer with transmission frequencies of between
1 MHz and 3 MHz is required for vessel analysis. A low
PRF facilitates venous vessels detection. Of the following
intracranial veins, the BVR, SpPS, StS, and TS are recommended for insonation. The intraobserver and interobserver variability is low if nonangle-corrected velocities
are used (Stolz et al. 2001). Venous flow velocities can vary
greatly in the vessels’ inflow and outflow regions. Flow
velocity analysis should only be performed if the vessel is
clearly visible. Measurements at junctions with other vessels should be avoided.
Deep Middle Cerebral Vein
Anatomic details: The DMCV is found in up to 80 % of cases
and receives blood from the insular region and the caudal
parts of the striatum. It runs directly adjacent to the MCA.
At the level of the optic chiasm it unites with the ACV to
form the BVR. Sometimes it may directly drain via a sylvian
vein into the CS.
Position and vessel identification: The vessel is visualized
via the transtemporal bone window using the axial midbrain plane (Fig.A2.75). We recommend starting insonation by identifying the color signal of the distal M1-MCA
segment in its transition to the M2 segment where the
DMCV is best insonated. In most cases a visual differentiation between the opposite color signals of the MCA and
DMCVwillnotbepossiblebecausethealiasingphenomenon using a low PRF will cover the weak venous signal. If
the distance between the artery and vein is large enough
Special Venous Anatomy and Ultrasound Anatomy
The following section is ordered according to the flow of
blood from the brain toward the heart, i. e., from the distal
intracranial to the proximal cervical vessels. Instructions
for insonation focus on duplex ultrasound only. However,
the reported normal values for flow velocities might also
have been derived from TCD studies. TCD also allows to
analyze intracranial venous vessels but even more that in
the arterialsystem hasclear limitationsbecause of the lack
of spatial orientation (Aaslid et al. 1989, Doepp et al. 1999,
Valdueza et al. 1996, Valdueza et al. 1998). A summary of
Fig. A2.75 MRI, T2-weighted image, axial (A ) and coronal plane
(B ). MR ce T1-weighted image, sagittal plane (C ). Insonation field
and transducer position for examination of the DMCV, BVR, ICV and
VG.
2 Vascular Anatomy and Structure of Ultrasound Examination44
Fig. A2.76 A Schematic drawing, axial plane. Note the blue DMCV
(arrows). B TCCS, transtemporal approach, midbrain axial plane.
Color-mode imaging of the DMCV visible as a small blue-coded
segment (arrows) posterior to an M2-MCA branch. C CTA, axial
MIP. Note the DMCV in close spatial relation, posterior of the MCA
(arrows). D Doppler spectrum analysis of the DMCV (flow velocity:
12/9 cm/s) with a flow away from the probe.
Basal Vein of Rosenthal (BVR)
Anatomic details: The BVR is a very constant vein draining
parts of the frontobasal brain, the hippocampal and parahippocampal region, the uncus, the limbic system, the
hypothalamus, the mesencephalon, the basal ganglia, the
capsula interna, and the insular region. The vessel can be
divided into three segments. In its classic variant, the
anterior segment evolves from the confluence of the
DMCV, inferior thalamostriatal vein and ACV. In its middle
segment it run parallels to the P2-PCA and proximal P3PCA segments in the ambient cistern circumscribing the
midbrain. The third, posterior segment starts at the back
end of the mesencephalon where it either merges into the
ICV or the VG and in only 8 % of cases directly into the StS.
However, in its middle segment it may also turn caudally
tomergeviathepetrosalveinandintotheSPS.
Position and vessel identification: The BVR is best insonated in its middle segment via the transtemporal bone
window using the axial midbrain plane. More distal parts
can be visualized in the thalamic plane (Fig. A2.75). We
recommend starting insonation by identifying the color
signal of the P2-PCA and P3-PCA segments. In a number of
cases the suspected PCA turns out to be the BVR. In this
segment, the BVR may have a larger diameter than the
PCA, which may then lead to a stronger color signal. In its
proximal segment the BVR Doppler signal is found lateral
of the P2-PCA segment with a flow direction toward the
transducer and in its distal segments it lies medial and
superior to the P2-PCA and P3-PCA segments with a flow
direction away from the transducer (Fig. A2.77). Sometimes, the BVR and the P3-PCA segment can be identified
as two parallel running blue-coded vessel segments.
Fig. A2.77 A Schematic drawing, axial plane: Note the blue-colored
BVR. B TCCS, transtemporal approach, midbrain to thalamic axial
plane: Color-mode imaging of the BVR as a blue-coded segment.
C MRI T2-weighted image, axial plane: Note the DMCV merging into
the BVR which encircles the midbrain (arrows). Note the PCA medial
to the BVR. D Doppler spectrum analysis of the BVR (flow velocity:
15/12 cm/s) with a flow away from the probe. Note the simultaneous
imaging of the PCA and BVR spectrum despite the color image
demonstrating only one vessel signal.
the DMCV may be detected over a short distance posterior
to the MCA. Doppler analysis reveals a venous spectrum in
64–91% of cases if the Doppler sample volume is positioned within the posterior border of the MCA color signal.
The flow direction is away from the probe (Fig. A2.76). The
transition into the BVR can usually not be visualized.
Normal values: Flow velocities: see Table A2.8 (p. 53).
Normal values: Flow velocities: See Table A2. 8 (p. 53).
Internal Cerebral Vein
Anatomic details: The ICV originates from the confluence
of the thalamostriatal vein and septal vein of the cavum
septum pellucidi at the level of the foramen of Monro. It
develops in 100 % of cases and follows a constant course
along the thalamus within the tela choroidea of the third
ventricle. It mainly drains the upper and medial aspects of
the thalamus.
Position and vessel identification: The ICV can only rarely
be insonated through the transtemporal bone window
using an approach between the thalamic and cella media
plane. The ipsilateral and also the contralateral ICV can be
detected with a flow away, respectively, toward the transducer. Compared with the transtemporal access (23 %)
(Stolz et al. 1999c) higher rates have been reported using
the unusual transfrontal bone window (52 %) (Stolz et al.
1999b) (Fig. A2.78).
Normal values: Flow velocities: see Table A2.8 (p. 53).