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Intravascular Ultrasound in the diagnosis
and treatment of chronic cerebrospinal
venous insufficiency
Salvatore J.A. Sclafani, MD, FSIR
American Access Care Physicians
Professor of Radiology, Surgery and Emergency Medicine
State University of New York Downstate Medical School
Brooklyn, New York
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Introduction
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The primary venous conduits that constitute the cerebrospinal venous circuit
include the right and left internal jugular vein (IJV), the right and left vertebral
veins and the azygous vein. These are the major outflow veins of the brain and
the spinal cord draining venous blood from the dural sinuses and from the
vertebral plexus and spinal veins. There are also secondary outflow veins,
namely the innominate veins and the superior vena cava. Augmentation of the
primary outflow veins can result from obstruction of the "inflow" veins that are
connected to the primary veins. These include the left renal vein that is
connected to the hemiazygous vein and the left common iliac vein that is
connected to the ascending lumbar vein.
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The recommended diagnostic algorithm utilizes Doppler ultrasound of the deep
cerebral veins, the IJVs and the vertebral veins in both the erect and supine
positions to assess the hemodynamic consequences of outflow derangement
and B-mode ultrasound to detect structural abnormalities. Doppler hemodynamic
manifestations include reversal or absence of flow and loss of normal postural
Chronic Cerebrospinal venous insufficiency (CCSVI) is a clinical syndrome that
results from outflow resistance of the veins that drain the brain and the spine. It
presents with chronic fatigue and temperature intolerance, short term memory
deficiencies and problems of concentration and executive processing,
headaches, spasticity and vision deficiencies, among others (1-3). CCSVI is
most commonly seen in patients with multiple sclerosis (4), but these symptoms
have been reported in patients with jugular stenoses and occlusions caused by
radical neck surgery, vascular access catheters, tumor compression,
hypercoagulable states, and trauma and without antecedent cause. (5-8)
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control in the erect position. A variety of B-mode abnormalities can be seen,
including occlusions, stenoses and hypoplasias, thickened, elongated and
immobile valves, septum and membranes. The detection of at least two of five
criteria correlates highly with the presence of CCSVI. (9)
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Magnetic resonance venography (MRV) and computed tomographic venography
(CTV) have been used by some to screen for CCSVI. These examinations allow
non-invasive visualization of the entirety of the veins of the neck, but in addition
can detect stenoses, hypoplasias and occlusions of these veins. Moreover these
imaging methods allow visualization of the central chest veins and the dural
sinuses prior to venography. Additionally, some efforts have been made to
quantify flow selectively in each of these critical veins.
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Venography remains the Gold Standard for the visualization of the jugular veins,
as well as of the azygous vein, a vein that cannot be imaged satisfactorily by
MRV, CTV or Ultrasound. To its advantage, venography can also visualize the
secondary veins, such as the left renal vein, the left common iliac vein and the
ascending lumbar vein. Venography can also assess subjectively flow, stasis
and reflux in these veins. To its advantage, the catheter study enables
subsequent treatment by angioplasty of stenoses of these veins.
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However, each of these imaging modalities has deficiencies that can negatively
influence treatment decisions. Surface ultrasound cannot visualize well the
confluens of the internal jugular vein and the subclavian vein because of the
impediment of the clavicle. Angling the transducer into the chest may
underestimate disease in this area. This is a critical deficiency because the area
under the clavicle is the most common location for pathology in CCSVI. Similarly,
the upper cervical jugular vein and the jugular bulb cannot be visualized by
ultrasound because of the limited acoustical window resulting from the spine,
mandible and skull. Moreover it is clear that ultrasound can evaluate completely
neither the azygous vein nor the brachiocephalic veins. In addition assessing the
degree of stenosis is unreliable by ultrasound.
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MRV and CTV cannot evaluate intraluminal pathology, such as the immobile
valves, webs, septations, membranes and duplications. As with ultrasound, they
cannot evaluate satisfactorily the azygous and hemiazygous veins even though
they are able to identify the compression syndromes of the renal vein and the
iliac vein. Furthermore they often detect spurious stenoses that are not confirmed
by venography. These stenoses may represent transient phasic narrowings or
may result from diminished flow above true stenoses commonly located at the
confluens region of the vein.
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Similarly venography also has difficulties identifying the intraluminal pathology
because density of the injected contrast may obscure these findings. Moreover
venographic determination of the size of the veins is rather subjective and may
mislead without multiple projections that would be necessary to assess this
characteristic. The IJV is often not a circular object; rather it is oval or complex in
shape. Thus determination of the diameter of the vein if often arbitrary and often
underestimates or underestimates the proper size of balloon for angioplasty. In
light of the high pressures necessary to disrupt this internal pathological stenosis,
proper sizing is crucial to avoidance of injury to the vein by overdilatation or early
recurrent stenosis by underdilatation.
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All of the luminographic studies, such as venography, MRV and CTV, suffer from
their "snapshot" nature. Outflow obstruction of the jugular veins results in slow
flow or stasis. Because there is an alternative cerebral outflow via the vertebral
veins, decompression results in diminished IJV volume these thin walled IJVs
that can collapse against rigid structures such as the spine, the carotid artery and
neck musculature. Accurate depiction of these veins requires multiple views,
such as imaging during inspiration and expiration, during flexion and extension,
and during rotations of the neck. These maneuvers cannot be done in real time
by MRV and CTV and doing them during venography is time-consuming to the
operator and results in increased radiation dose to the patient.
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Intravascular Ultrasound
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Intravascular ultrasound provides benefits that can address many of the
deficiencies of venography, surface Duplex examination, CTV and MRV. The
most common indications for intravascular ultrasound have been in the
evaluation and treatment of arterial disease, notably in the management of
coronary artery disease. Its ability to differentiate various tissue characteristics
enables one to assess plaque morphology, detect lipid and calcium deposits and
elaborate the degree and distribution of calcification within atherosclerotic
plaques. It can thus help evaluate the vulnerable soft, un-ruptured plaque. IVUS
is useful in characterization of both the vessel wall and the endothelium. It can
assess mural and endothelial thickness and clarify whether narrowings are the
result of intimal or mural disease.
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IVUS has been shown to provide a more accurate assessment of vessel
circumference and cross sectional area and thus is useful in detecting critical
stenoses. Such elegant analysis of the dimensions of the vessel allows a more
accurate selection of balloon size, thus reducing risk of injury and providing more
effective angioplasty. IVUS allows improved visualization of intimal thickening
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after angioplasty. Moreover, IVUS enables the operator to see how well apposed
stents are to the intima and thus guides the need for additional angioplasty to
reduce separation between intima and stent. This may facilitate
endothelialization of the stent.
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Although the vast majority of publications on IVUS relate to the coronary arteries,
authors have reported on the value of IVUS in many other conditions, both within
arteries and veins. (10)
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More recently, benefits have been reported in a number of peripheral arterial
applications. Some of the same advantages of IVUS have been exploited in the
treatment of peripheral atherosclerotic disease (11). Plaque morphology, more
accurate determination of vessel size and degree of stenosis, and tissue
characterization by IVUS have been added to the information from angioplasty
and thus facilitating and enhancing atherectomy and stenting of peripheral, renal
and carotid atherosclerosis. (12)
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Authors have also been enthusiastic about using IVUS in the deployment of
aortic endographs. More accurate measurement of vessel circumference and the
sonographic visualization of the location of aortic branches have allowed greater
precision in determining both upper and lower landing zones. The addition of
IVUS can alter the plans derived by CTA, contradicting CT’s determination that
endovascular stenting was either feasible or futile.
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IVUS has been shown to facilitate the diagnosis of aortic dissection. It is highly
effective in detecting entry points along the dissected aorta. This can facilitate
placement of stents and reduce need for operative intervention. Moreover, IVUS
has been shown to be an effective guidance method during fenestration
procedures. (13-15)
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The use of IVUS in cases of traumatic aortic injury has been shown to improve
diagnosis, especially in patients with equivocal aortography, by allowing
differentiation of ductus diverticulum and pseudoaneurysm. Indeed, it was shown
to be superior to aortography in one series of fourteen patients with a sensitivity
of 92% and a specificity of 100%. (16)
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While much less commonly reported than use in arterial disease, IVUS has
shown merit in a variety of venous pathologies and treatments. Because of its
portability, IVUS as a guidance method has been recommended for placement of
inferior vena caval filters. The ability to precisely determine the circumference of
the caval lumen and to localize all renal vein tributaries without contrast media or
ionizing radiation has advantages. Filters can be deployed in an intensive care
unit, thus avoiding risks of transport of critically ill patients. The ability to perform
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the procedure without the use of iodinated contrast media is such patients is a
distinct advantage.
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The use of IVUS for venous disease in patients with renal insufficiency or in
patients with potentially life threatening allergies to contrast media has also been
reported in management of dialysis grafts and fistulae, and central venous
stenosis. (17-18)
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Negen and Raju have argued effectively for the use of IVUS in patients with
venous disease, notably in chronic iliac vein stenosis and occlusions. They point
to the fact that hemodynamic data so helpful in arterial obstructions is often
limited or equivocal in venous disease because of small differences. The
significance of pull-through pressure gradients is difficult to interpret. Small
degrees of pressure differential may indeed be significant, given the large
volumes and high compliance. Rather morphological area stenosis of 50%
seems to provide some predictive value of clinical improvement after angioplasty.
They recognize the rather irregular shape of the iliac vein and the difficulties in
using single view diameters to make stenosis measurements. Further they point
out that intraluminal abnormalities, such as immobile valves, subintimal edema,
and echogenic material, probably representing trabeculae, septa, and webs,
cannot be seen by venography which obscures them with dense contrast media.
(19-21)
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To date I can find nothing in the literature that describes the IVUS findings of
CCSVI, nor one that reports on abnormalities of the internal jugular vein and the
azygous vein in CCSVI or other diseases.
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Technical considerations
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Intravascular ultrasound is a technique that places within a hollow structure, such
as a vein or artery, a catheter or a wire containing a miniaturized phased array
ultrasonic transducer that sends out frequencies of 10 to 50 megahertz and then
captures reflections off near objects. The catheter or wire is 3.2-8.2 French in
diameter and is attached externally to a cart that performs the reformations and
calculations. The systems are also equipped with a motorized unit that can
retract the catheter at a fixed rate. The device can be introduced through a
sheath of 6-9 Fr diameters and advanced over a 0.01inch-0.038 inch guidewire
by either over the wire or rapid exchange techniques. (11)
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Images that are created are cross sectional B-mode images with resolution of
110-150 microns and penetration of about 20 millimeters. In addition to cross
sectional images, modern units can create longitudinal reformations that some
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believe provide images that are more revealing views of length of stenosis and
degree of narrowing. However, this requires use of a motorized catheter driver.
Some vendors have now made available wires that can capture hemodynamic
data such as Doppler flow rates, pressures and gradients. Assessment of
stenotic and microvascular resistance is now possible, although the utility of this
information in CCSVI is not established.
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Other methodologies include ChromaFlo and VH (Virtual Histology). Chromaflow
detects blood flow and represents it on imaging with a red color. Thus this nonquantifiable presentation of flow aids in differentiating tissue types that are similar
to flowing blood on the B-mode images. VH-IVUS is a spectrum analysis of
IVUS-derived radiofrequency (RF) data acquired at the top of the R wave. It
allows reconstruction of a color coded map showing a more detailed analysis of
plaque composition and morphology. It is suggested that VH-IVUS has the ability
to detect lesions that predict high risk lesions in coronary artery disease. It is
possible that such manipulations may distinguish various tissue types in CCSVI
and may be able to predict response to angioplasty. However this feature does
not yet exist.
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Finally, IVUS presents a real-time cross sectional view. During that interrogation
it is possible to analyze various questionable areas of the venous anatomy while
performing a variety of physiological maneuvers such as Valsalva and reverse
Valsalva, inspiration and expiration, flexion and extension and varying degrees of
rotation. We shall see that there is great advantage to such maneuvers in the
evaluation of CCSVI.
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Justification for IVUS in CCSVI
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IVUS is indicated as a primary evaluation of intraluminal venous pathology, as a
tool for stenosis analysis, as a method of detecting pressure gradients, as an aid
for assessing inconstant or atypical narrowings and as a post-angioplasty exam.
In unusual circumstances, IVUS can allow the procedure without use of iodinated
contrast media in patients who have had potentially life-threatening allergic
reactions to contrast media or who have severe renal insufficiency but do not yet
require chronic hemodialysis. IVUS can provide sufficient information to perform
this procedure without venography although venography does make this
procedure easier.
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A recent presentation of a joint meeting of the European Committee on
Research in MS (ECTRIMS) and the American Committee on Research in MS
(ACTRIMS) reported on a comparison of jugular venous pathology from
specimens obtained at autopsy from cadavers of patients with multiple sclerosis
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and of people who died of unrelated illness. (22) The authors discovered that
stenoses were common in both group. What distinguished the MS group from the
non-MS group was a preponderance of intraluminal lesions, such as immobile or
inverted valves and other valvular deformities, septum, webs, membranes and
duplications. This is consistent with the theory that CCSVI is the result of
malformation of the maturation of the fetal cardinal system of cerebrospinal veins
into the adult system (23).
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The preponderance of intraluminal lesions suggests that an intraluminal study is
appropriate for the complete diagnosis of this pathology. Venography can
demonstrate the major stenotic lesions. However superimposition of valvular
cusps and reflux opacification of the vessel distal to a stenosis may obscure
them. Moreover, venography cannot distinguish the various etiologies of such
stenoses. Strictures, hypoplasia, and valvular stenosis can look identical on
venography which provides a simple lumenogram. Endoluminal studies are
superior to contrast studies that obscure such pathology by the necessary
density of the contrast media. Negen and Raju have shown evidence that such
venous pathology in the iliac vein is unrecognized by venography and yet well
seen by IVUS. (21)
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IVUS is also valuable in evaluating transient narrowings that are not fixed and
may be physiological. Moreover veins often have irregular circumference;
compressed by surrounding muscles, arteries and bones they may take varied
and unusual contours that make it difficult to determine their diameter. As such,
stenosis analysis may be extraordinarily difficult and inaccurate. Simple diameter
measurements rarely provide a good maker of stenosis. Nor are such diameter
measurements sufficient to choose an appropriate balloon size for angioplasty.
Finally IVUS provides an excellent methodology of evaluating the effectiveness
of venoplasty and valvuloplasty. The elimination of immobile valves is particularly
well seen on IVUS. Complications of angioplasty are also better visualized by
IVUS. Thrombus and dissections are readily seen on IVUS.
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Performing the examination
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I perform diagnosis and treatment of CCSVI using fluoroscopy, venography,
intravascular ultrasound and external ultrasound access guidance. The
procedure is performed under local anesthesia and with micropuncture access.
Vascular entry is obtained under external ultrasound guidance through a left
inguinal approach, to enter the saphenous vein at the saphenofemoral junction. A
10 French sheath is introduced and positioned above the right atrium in the
superior vena cava. The sheath is positioned and all instrumentation is moved
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through the sheath, as an essential protection because the very small wire
required to track the IVUS buckles into the heart and mat cause arrhythmias.
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Once the sheath is in place, all, or at least most, of the catheterizations are
performed over the 0.014 inch guidewire needed for the IVUS. I perform
venography followed by IVUS for each of the three major cerebrospinal outflow
veins, namely the right and left IJV and the azygous vein. I perform venography
alone in the majority of transverse sinuses, in the left renal vein, in the left
common and external iliac vein and in the left ascending lumbar vein. I do not
recommend routine IVUS of the left renal vein or the left iliac vein because these
veins are rarely associated with immobile valves. However when stenoses or
prominent collaterals are identified, IVUS is used. When compression of the
renal or iliac veins is seen, the diagnosis of Nutcracker or May Thurner syndrome
can be made. IVUS is then critical to accurate sizing of these veins to reduce risk
of migration.
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With the guidewire in the transverse sinus and using a rapid exchange system,
the IVUS is positioned in the jugular bulb and then withdrawn manually at
deliberate speed down into the innominate vein. I do not use the automated pullback device because such devices were developed for coronary use and the pull
back moves too slowly to be practical for the long length of the jugular vein.
Critical areas to evaluate include the upper internal jugular vein at the C-2 level,
the mid jugular vein where venous compression by the carotid artery or the strap
muscles occurs and, most importantly in the lower jugular vein at the confluens
with the subclavian vein where most of the pathology is located. (Figure 1)
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After azygous venography IVUS is performed throughout the azygous vein,
extending as far down the azygous and hemiazygous as possible. Transient
narrowings are common in the azygous. Inspection of narrowings throughout the
ascending azygous should include inspiration and expiration views as this area
common dilates during inspiration. I do not treat transient narrowings. The area
of the junction of the ascending azygous and its arch is inspected in great detail.
Subtle immobile valves in the azygous vein are often unrecognizable on
venography and are often visualized only by IVUS. (Figure 2)
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B-mode imaging in both the cross sectional and longitudinal views are important.
The cross-section image looks at the circumference of the vein, and reflective
tissue such as webs, membranes, septums and valves. The longitudinal view
gives a good view of collateral entries, longitudinal views of stenoses and a
different view of intraluminal pathology. I have not relied upon ChromaFlo or
Virtual Histology at this time.
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Diagnostic IVUS: findings
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Normal Internal Jugular vein (Figure 1)
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On IVUS, the IJV varies in its appearance depending upon location in the neck.
The upper segment (J3) starts as a larger structure (superior jugular bulb) that
quickly diminishes in circumference. It occasionally flattens as it courses over the
second cervical vertebra before expanding in diameter in the mid portion of the
neck (J2). Often tributaries are seen in this region. A second crescentic
indentation, representing the compression by the carotid artery, may be seen in
this region. The lower jugular vein is normally dilated as it joins the subclavian
vein (inferior bulb).
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Normal Azygous venous system (Figure 2)
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The azygous vein is a continuation of the right ascending lumbar vein; the
hemiazygous vein is a continuation of the left ascending lumbar vein or a branch
of the left renal vein. The accessory hemiazygous vein is a continuation of the
upper left intercostal veins and may drain into the left innominate vein or into the
azygous vein. Valves are typically present in the arch of the azygous vein; they
may be multiple.
The IJVs are the primary venous outlets for the cerebral blood volume when a
human is supine. The vertebral veins and the vertebral plexus assume this
function in the erect position. The sigmoid sinus, the terminal component of the
transverse sinus, combines with the inferior petrosal sinus to form the superior
jugular bulb. The vein runs a continuous course down the neck in the lateral
aspect of the carotid sheath where it dilates (inferior bulb) before enter the
innominate vein at its confluens with the subclavian vein. Valves, usually
biscuspid, are located near the confluens are present in about 85% of humans
and. There may be more than one set of valves. Major branches of the IJV
include the inferior petrosal sinus, pharyngeal vein, the common facial vein, the
lingual vein, and superior and middle thyroid veins. In CCSVI IJV outflow is
compromised
The azygous vein is a critical conduit that drains the thoracic and, to some
degree, the lumbar spinal venous circulation. The central and radial spinal veins,
draining via vertebral plexuses and anterior and posterior medullary veins
ultimately form intervertebral veins that connect with intercostal veins before
draining into the azygous and hemiazygous veins. These spinal veins and
plexuses are connected directly to the venous drainage of the brainstem and the
cervical and lumbar spinal cord, via anterior and posterior medial spinal veins
and dural plexuses.
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On IVUS the azygous vein is usually a rounded structure with little sonolucency
in the wall as all veins have minimal muscularis. At the level of the aorta, the vein
may be flattened or narrowed. One sees segmental veins entering it; segmental
arteries are posterior to the vein and may temporarily indent the vein. At the
junction of the ascending azygous vein with the arch of the azygous, a large
draining vein may enter it. This is the continuation of the accessory hemiazygous
vein. Valves are usually present within the arch of the azygous vein. When
thickened they are visible, echogenic and show limited motion.
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Abnormal
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Assessment of all valvular structures is very important as the majority of
abnormalities are located in areas of valves and most abnormalities are
malformations of valves. Intraluminal bright signals can be misinterpreted as
artifacts but they should be considered very carefully. Moving the transducer and
then returning to the same area looking for the persistent bright reflections in the
same location is a helpful tool in eliminating artifacts from serious consideration.
The examination is reviewed both in cross sectional view and in the longitudinal
mode.
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Valves (Figure 3)
Venography provides a comprehensive technique for detection of stenoses of the
major cerebrospinal veins. These stenoses are usually well seen on contrast
studies. However, the nature of such stenoses may be less clear. IVUS provides
important data regarding the nature of stenoses: the anatomic nature of
stenoses, the phasic nature of stenoses and whether they are intrinsic or
extrinsic in nature.
Normal valves are almost imperceptible: gossamer structures that are not easily
visible. Abnormal valves are more easily seen. They are characterized by
irregular thickening, poor mobility and bulging cusps. Thickening may be small
foci of echogenic spots measuring less than a millimeter or longer areas of
thickening. These are highly echogenic. These thickened areas may form a
circular or oval circumference. The circumference may progressively decrease as
the transducer is moved down the vein toward the chest. The valve appears to
sway to and fro. One sees that the edges of these valves move little and never
extend to the lateral walls of the vein. Uncommonly the valve may be seen en
face at one level. On the longitudinal view, the lumen may be narrow and there
may be two parallel signals (the “double echo" sign) that represent echoes off the
valve and off the outer wall of the vein.
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Septum (Figure 4)
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Membrane (Figure 5)
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Web (Figure 6)
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Thrombus (Figure 7)
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Diffuse narrowings
Septums are seen as thin vertical bands extending up and down the vein. They
may be thin or have areas of patchy echogenicity similar to the leaflets of valves.
They may be compared to elongated valve leaflets. One can sometimes follow
these bands to their attachment to the wall proximally or distally, forming a sort of
"windsock". Some septum form a blind ending sack dividing the vein into two
separate chambers, only one of which is in continuity with the cephalad lumen,
analogous to a dissection. The "false" lumen may bulge and compress the "true"
lumen on Valsalva maneuver. Septum may also show thickening and increased
echogenicity, similar to abnormal valves. Differentiation relies upon the absence
of an opposing valve leaflet. The septum appears to be taut against the IVUS
probe.
A membrane is a horizontal band of tissue, like a valve that extends transversely
across the vein as well. On the longitudinal view, septum shows as relatively thin
lines of tissue running parallel to the venous wall. They may be very difficult to
visualize on IVUS because of their horizontal nature.
Webs are bands of tissue remaining within the lumen of the vein. They are
thought to be sequellae of the de-differentiation/re-differentiation of the veins
during the transition from the fetal cardinal system into the adult system. Webs
are another abnormality that is often not recognizable by venography because of
its location within the lumen. Webs are represented as echogenic material within
the vein lumen that is persistent and located in the same location during several
interrogations with the IVUS probe. They are most commonly seen within the
azygous vein and less commonly in the jugular system. On longitudinal view
they are usually seen as random areas of high echogenicity.
Thrombus is another echogenic material within the lumen. Clot tends to be
thicker and amorphous and has a speckled and more brightly echogenic
character. It is also inconstant in location and less reproducible.
Intravascular ultrasound is very useful in assessing and differentiating the many
causes of long narrowed segments Diffuse luminal narrowing can be a phasic,
inconstant phenomenon or it can be caused by compression syndromes, by
hypoplasia, by intimal hyperplasia or by post-thrombotic recanalization. Each of
these presents venographically as a narrow contrast column. Differentiating
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these problems is sometimes challenging but important as different treatment
strategies are warranted. Treatments vary from doing nothing to stenting.
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Inconstant narrowing (Figure 8)
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Venography, as a static sequence, does not allow dynamic imaging because of
time constraints and radiation exposure. Imaging with IVUS is free from these
impediments and allows one to place the transducer at the point of interest and
perform a variety of maneuvers. Maneuvers that increase flow by activation of
the thoracic pump, such as deep expiration, may increase flow through the vein.
Changing neck position, such as flexion and extension, internal or external
rotation may reduce flow by increasing the pressure on the IJV.
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Other compressions are more significant and IVUS can plan an important role in
their evaluation. The Nutcracker and the May-Thurner syndrome are clinically
manifested obstruction of the left renal vein and left common iliac vein that are
caused by compression of these veins between two structures. IVUS shows
complete flattening of the vein, associated with a prominent hemiazygous, or
renal vein or, is
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Long luminal narrowings (Figure 9 )
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However, IVUS has the potential to differentiate these problems, based upon the
echogenicity of the offending pathology. Hypoplasia shows a narrow lumen but
the echogenicity of the wall may be normal. In a recanalized vessel, IVUS may
show intraluminal thrombus lining the interior of the vein. Thrombus is highly
echogenic and often can be differentiated from the reflections of the wall itself.
The echogenic areas may be interspersed with areas of diminished echogenicity.
Inconstant narrowings are a physiological effect frequently associated with fixed
stenoses that are located more centrally in the vein. The dual outflow system of
the cerebral venous system through the internal jugular veins and the vertebral
veins and vertebral plexus allows the obstructed vein to decompress. Because of
the compliance of the veins, the vein can collapse. Such collapse may be more
pronounced due to pressure upon this vein by the internal or common carotid
artery or compressed by muscles.
Long luminal narrowings may be caused by hypoplasia, intimal hyperplasia, postthrombotic recanalization, or perivenous inflammatory processes. Venographic
appearance of these entities can be virtually indistinguishable. When the luminal
diameter is completely collapsed, differentiation of these abnormalities can be
impossible. While IVUS may have theoretical advantages over venography in
evaluating some of these conditions, there is little data published in the literature
on this subject in general and none as it relates to CCSVI or jugular veins.
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Echogenicity will be less for intimal hyperplasia than for thrombus lining the
vessel wall. Perivenous inflammation may be detectable as separate from the
vein itself.
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443
Use of IVUS for balloon selection (Table 1, Figure
10)
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Balloon sizing is a great challenge in treating stenoses of the internal jugular
veins. Unlike the azygous vein and arteries which have a relatively uniform
circular shape, the internal jugular veins do not. They may have a round, oval or
multifaceted shape. Venography cannot accurately detect these shapes without
the use of multiple views. Moreover, maximum and minimum diameters may be
so disparate that simple estimates may grossly underestimate or overestimate
the balloon size selection. Because these stenoses usually require large balloons
and high pressures, improper sizing may result in serious complications such as
dissection, tears and occlusions or inadequate distension and ineffective
treatment.
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Analysis by IVUS makes quite clear the deficiencies of venography. The cross
sectional anatomy of the vein and the variation of size based on phase of
respiration may it clear that cross sectional area (circumference) is the superior
criteria for assessing size of the vein and for selecting the appropriate balloon for
venoplasty or valvuloplasty.
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Post intervention assessment
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IVUS is helpful in monitoring the treatment. Because many of the intraluminal
pathological states are only clearly detectable by IVUS, assessment of the postangioplasty state is best done by IVUS. Incomplete opening of immobile valves
and incomplete disruptions of webs and septum are readily detected by IVUS.
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The major complications of treatment of CCSVI are procedural injuries such as
lacerations, valvular avulsions, and dissections. They may be difficult to
differentiate on venography alone but are easily differentiated on IVUS. Further
post-procedural stenosis caused by intimal hyperplasia and in-stent stenosis can
be detected and quantified.
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Summary
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Intravascular ultrasound is an essential imaging modality that facilitates detection
of the intraluminal pathology associated with CCSVI, including valve
abnormalities, webs and septum. It facilitates differentiation of a variety of
stenotic lesions. IVUS allows precision in sizing angioplasty balloons and is an
excellent method of judging treatment results and complications. It should be
considered part of the standard of care.
478
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479
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Captions for illustrations
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Figure 1. Normal internal jugular IVUS
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Index: 1. Transverse sinus tributary, possibly posterior cerebral vein or condylar
emissary vein. 2. Inferior petrosal vein entering sigmoid sinus; 3. Pharyngeal
veins in upper IJV; 4. Facial vein; 5. Superior thyroid veins; 6. Inferior thyroid
veins; 7. Confluens of IJV with subclavian vein.
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Figure 2: Normal azygous IVUS
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Legend: 1. intercostal artery (asterisk) indenting the azygous vein, 2. Intercostal
vein; 3. Typical compression of mid-portion of the ascending azygous vein; 4.
Spine; 5. Aorta; 6.orifice of accessory hemiazygous vein.
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Figure 3: Valvular stenosis
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Figure 3B: Total valvular obstruction: 1. Axial and longitudinal views show a
widely patent upper internal jugular vein. There is strong lumen/intimal interface.
2. More inferiorly as the transducer traverses the obstruction, a lumen is not
visible on either longitudinal or axial views.
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Figure 4 Septum
IVUS from the transverse sinus (A) to the confluens with the subclavian vein (B).
Note compression of the carotid artery of the J2 segment of the IJV (F).
IVUS of the azygous vein IVUS from distal ascending portion (A) to junction of
the arch with the superior vena cava (F)
Figure 3A: Partial valvular stenosis with associated webs: 1. shows 60% stenosis
of the IJV at the confluens with the subclavian vein. Contast contour is smooth. 2.
The IVUS probe at site of interrogation. 3. There is evidence of echogenic
thickening at the edges of this immobile valve (white arrows). This represents the
stenosis. The outer wall of the vein (black arrows) is much larger than the area
that contains the contrast media
Figure 4A: Internal jugular septum: 1. Arrows point to a subtle "jet" of contrast at
the confluens. This stenosis was missed by the first angiographer. 2. Axial IVUS
shows the septum extending down to the innominate vein confluens (arrows). 3.
Longitudinal IVUS reveals the septum dividing the lumen (arrowheads). 4.
Angioplasty reveals the area of stenosis. High pressures were required to relieve
this stenosis.
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Figure 4B: Occult Azygous septum: 1.Venography was interpreted as being
normal, even in retrospect. Arrow points to the area of abnormality seen on
IVUS. 2. Axial IVUS shows intraluminal echogenic tissue (arrows). 3.
Longitudinal IVUS clearly demonstrates the intraluminal tissue.
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Figure 5: Membrane.
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Figure 6: Web in Azygous:
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Figure 7: Thrombus in dural sinus and IJV:
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Figure 8: Phasic narrowing of azygous vein
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Figure 9: Intimal hyperplasia
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Figure 9B: Intimal Hyperplasia within stent: 1. Venography shows occlusion of a
stent placed during treatment of CCSVI by another physician. Differentiation of
thrombus and intimal hyperplasia cannot be discerned. 2. After first attempt of
Membranes are transverse flaps that obstruct flow. They likely represent
malformed valve tissue. Venography (A) with the catheter cephalad to the
membrane appears normal. With the catheter withdrawn centrally (B), the
membrane becomes visible (arrows). It is postulated that the catheter has
pushed the membrane open against the lateral wall in Figure 7A.
Webs are small tangles of tissue within the lumen of the vein possibly remnants
of the cardinal vein maturation into the adult veins. 1. Arrows point to small
areas of echogenic material. They may represent webs. However single areas of
abnormal thickening of a valve could cause such an appearance. 2. The
longitudinal view illustrates that this tissue has the random nature of a web (white
circle) rather than of a valve.
A. Thrombus fills the lumen and surrounds the transducer (curved arrow) which
nearly fills the lumen. The thrombus is displayed as bright mottled echogenic
reflections. The venous wall is well seen (straight arrow); in this case it is located
within the dural sinus characterized by a triangular shape. B.The brightly
echogenic thrombus extends into the internal jugular vein.
Venography (not shown) revealed a long tapered narrowing of the ascending part
of the azygous vein. IVUS, performed in both expiration and inspiration, clearly
shows the phasic nature of this stenosis. No benefit will be derived from
venoplasty because IVUS has demonstrated that this is not a fixed stenosis.
Figure 9A: Intimal hyperplasia after thrombosis recanalization: 1. It is difficult to
see the stenosis on this axial image because of the lack of echogenicity of the
cause. 2. The longitudinal view shows this to great advantage. Arrows point to
the edge of intimal which is markedly thickened.
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suction aspiration, axial IVUS differentiates echogenic stent (black arrow) from
echolucent intimal hyperplasia (white arrow) from echogenic thrombus (dotted
arrow).
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Figure 10: Using IVUS for treatment planning
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Figure 10B: Quantifying stenosis: 1. Venography illustrates overdilation of the
IJV during procedure done by a prior proceduralist. This stenosis was mostly
likely caused by angioplasty of the incorrect segment or restenosis. 2. Curved
echo represents wall of stenosed valves without remainder of vein excluded from
direct flow. 3. Cross sectional measurement of both inner stenotic lumen and
outer edge of wall, allows accurate calculation of percentage stenosis of 61.7%
as opposed to values derived from diameter measurements ranging from 13% to
52%.
Figure 10A: Assessing vein size before angioplasty: This axial IVUS illustrates
some of the difficulty in assessing dimensions of veins and in choosing the
proper balloon for safe and effective treatment of stenoses. Depending on
orientations of the central ray of the fluoroscope and the vein axis, widely
discrepant estimations of size may occur. The shortest diameter is less that 6
millimeters and the longest diameter is greater than 11 millimeters. Too small a
balloon may be ineffective or result in short term clinical response. Too large a
balloon may overdistend and injure the vein, thus increasing risk of stenosis or
tear of the vein wall. Seeking a balloon 50% greater in size than this vein would
indicate a balloon with CSA of about 100 mm2. A ...mm balloon was chosen.
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Table 1 Angioplasty balloon cross sectional area
Balloon Diameter (mm)
CSA (mm2)
Balloon Diameter (mm)
CSA (mm2)
5
2
12
113
6
28
14
154
7
38
16
201
8
50
18
254
9
63
20
314
10
79
22
380