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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3609_Библиотеки_им_академика_М_И_Перельмана
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R. Kumar et al.
dal structure, i.e. the normal vasculature (arteries and veins),
should be preserved. To achieve this goal, each feeding artery
needs to be examined by selective catheterization, and the
drainage veins need to be identied before occlusion so that
the entire angio-architecture of the AVM can be understood.
The shunts within the AVM, whether high ow, low ow, or
mixed type, need to be identied especially while using glue
to determine the optimal glue concentration for embolization. High-ow shunts require higher concentrations,
whereas low-ow shunts require lower concentrations of the
embolization materials. The venous segment that is directly
connected to the arteriovenous shunts is known as the primary vein [5]. They can have multiple arterial feeders.
Secondary veins deviate from the primary vein to drain into
the venous sinus [5]. Occlusion of the primary veins obliterates the venous drainage of an AVM, and once they are
occluded, blood ow from any non-occluded feeder will
increase the pressure inside the AVM, leading to its rupture.
Hence, the entire nidus needs to be obliterated before occlusion of the primary vein(s). Occlusion of a secondary vein
does not entirely compromise the venous drainage of an
AVM and hence does not increase the risk of the rupture of
an AVM fed by non-occluded arteries. AVM embolization
should ideally be done in a single session. Multiple sessions
increase the risk of AVM rupture. Embolization can be done
via trans-arterial route or transvenous route.
Trans-arterial approach: Trans-arterial route is preferred for AVM embolization in most of the cases. In this
approach, the main feeding artery of an AVM is catheterized,
and the microcatheter is placed as close to the nidus as possible. The embolic agent is then delivered into the nidus continuously until the initial few millimetres of the primary
draining vein are occluded or there is reux of the embolization material. Trapping the microcatheter tip with the help of
injectable coils and glue can prevent reux and allow uninterrupted delivery of the embolic agent [8]. This technique
can be performed if a detachable tip microcatheter (Apollo,
Sonic) is used to deliver the embolic agent and another
microcatheter needs to be used for the delivery of the coils
and glue to trap the microcatheter tip [8]. Reux of the
embolic agent can trap the microcatheter tip and make it hard
to withdraw, leading to vessel rupture in some cases. This is
especially problematic with non-detachable tip microcatheters (Magic, Marathon). However if a detachable microcatheter is used, reux of the embolic material can be allowed up
to the detachment point, and such an amount of reux can
even provide the advantage of the trapped microcatheter or
pressure cooker technique described formerly without the
need for an additional microcatheter. The delivery speed of
the embolic agent can be controlled by wedging the microcatheter tip. Directing the tip towards the vessel wall slows
down the rate of delivery and is useful while embolizing
high-ow AVMs where rapid delivery of the embolic agent
might occlude the draining vein before lling the nidus
resulting in intranidal pressure build-up. Any increase in the
intranidal pressure increases the risk of AVM rupture. In
AVMs having two dominant feeders, simultaneous catheterization of the two feeders with two separate microcatheters
can be done to perform simultaneous embolization of the
nidus via both feeders. This technique minimizes the risk of
intranidal pressure build-up due to occlusion of the venous
drainage during embolization via single feeder. However,
this technique requires two operators for simultaneous
embolization. If the main arterial feeder of an AVM is difcult to catheterize and the microcatheter tip remains distant
from the nidus, the delivery of the embolic agent can be done
by making a column of the embolic material in front of the
microcatheter tip and then pushing it by injecting more and
more embolic material.
Transvenous approach: This approach has gained popularity in recent times and is preferred in the case of small
(≤3cm), deep-seated AVMs or AVMs with narrow-calibre
feeders that are difcult to access via trans-arterial route.
Accessing an AVM via transvenous route can also be very
difcult owing to tortuosity of the cerebral veins draining the
AVM.Big AVMs have large venous outow and are easy to
access via transvenous route. But a large venous outow prevents proper intranidal deposition of the embolic material
injected through the venous side. Another concern is early
occlusion of the draining vein before occluding the nidus,
which may increase the intranidal pressure leading to rupture. Deep-seated AVMs are supplied by the lenticulostriate
or choroidal arteries, which are difcult to access via the
trans-arterial route, whereas such AVMs drain into the deep
venous system, which is easily accessible via the transvenous route. AVMs with multiple venous outow are difcult
to embolize via transvenous route because of lesser chance
of complete intranidal deposition of the embolic material.
Hence, transvenous embolization should be done in AVMs
with a single venous outow. Transvenous embolization is
carried out under a roadmap provided by a catheter placed on
the arterial side. Super-selective angiography is obtained
using a microcatheter placed on the arterial side to delineate
the AVM architecture before starting embolization. The
microcatheter on the venous side should be placed as close to
the nidus as possible, and the venous outow should be preserved until complete obliteration of the nidus. Temporary
systemic hypotension or temporary balloon occlusion of the
main feeder may aid in proper intranidal deposition of the
embolic material by reducing the arterial ow into the AVM
[9]. Such technique also minimizes the risk of AVM rupture
due to intranidal pressure build-up. The pressure cooker
30 Endovascular Approach forCurative Embolization ofBrain AVMs: Insights fromAngio-architectonics andAngio-anatomy
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technique can be applied to trap the microcatheter tip on the
venous side [10]. This technique prevents reux of the
embolic agent into the veins and allows better penetration of
the nidus [10].
Demonstration ofClinical Cases ofCurative
Embolization Using NBCA withTechnical
Pointers
Case 1
A 24-year-old male patient presented with recurrent posterior parietal and ventricular bleed. On DSA, an AVM was
found, and patient was taken for curative embolization
(Figs.30.14, 30.15, and 30.16).
The patient was taken up for embolization under general
anaesthesia. A right femoral approach was used. A 4F
head- hunter diagnostic catheter was advanced into the internal carotid artery under roadmap guidance. Thereafter, a
1.5F Marathon ow-guided microcatheter was navigated
into the nidus, and multiple compartments were catheterized.
With repeated injections, the various compartments of the
nidus were delineated, and stulous as well as plexiform
compartments were identied. As shown in Fig.30.17, different concentrations of glue were chosen according to the
nidal characteristics, and multiple injections were done.
Different positions of the catheter tip in relation to the
feeding pedicle also decide the ow characteristics
(Figs.30.18 and 30.19). Here it becomes important to understand the ow characteristics in the vessel. What is important
to know is that the centre of the vessel has laminar ow, and
as one proceeds towards the periphery, the ow becomes
more and more turbulent due to the interaction with the
endothelium. Therefore as a corollary, if a catheter is coaxial
in the vessel, the embolic material will travel further and
faster, whereas if the catheter is releasing the embolic material towards the edge of the vessel, it will slow down and
polymerize quickly. These can be used in different permutations and combinations according to the ow characteristics
in the vessel and the nidus (Fig.30.20).
Case 2
An 11-year-old female patient presented with thunderclap
headache and unconsciousness. CT showed a callosal and
ventricular bleed. DSA showed an AVM (Figs.30.21, 30.22,
30.23, and 30.24).
The patient was taken up for embolization under general
anaesthesia. A right femoral approach was used. A 4F headhunter diagnostic catheter was advanced into the internal
carotid artery under roadmap guidance. Thereafter, a 1.5F
Marathon ow-guided microcatheter was navigated into the
nidus, and multiple compartments were catheterized. In this
present case, there were no large arterial pedicles supplying
the AVM, and the twigs were not seen on 2D DSA. A cone
beam CT angiographic exploration was done (Fig.30.22).
With these ultra-high-resolution images used as roadmap,
the long and short callosal arteries were canulated individually using Magic 1.2 ow-guided microcatheters. With
repeated injections, the various compartments of the nidus
were delineated, and stulous as well as plexiform compartments were identied. As shown in Fig.30.17, different concentrations of glue were chosen according to the nidal
characteristics, and multiple injections were done
(Figs.30.25 and 30.26).
Fig. 30.14 DSA showing the supply to the Neopallial AVM from the MCA as well as from the PCA.Interesting to see that the deep supply is not
visible, even though the lesion is crossing the phylogenetic boundary
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Fig. 30.15 Cone beam CT angiographic exploration of the AVM
showing the expected deep supply from the Choroid Plexus by virtue of
the lesion being in the “Epihippocampal Zone” (Arrows). It is also
interesting to see the activation of the vessels in the tentorial edge and
the secondary venous drainage towards the Superior Sagittal Sinus
(Arrowheads). Additionally, this being a sulcal subtype of Neopallial
AVM, additional Dural supply is getting activated (arrows) from the
marginal tentorial artery
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Fig. 30.16 Super-selective catheterization of the different compartments of the AVM and progressive obliteration of the nidus with NBCA
injections
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Fig. 30.17 For pure plexiform nidus types, the concentration of
NBCA chosen for embolization tends to be in the 17–23% range. For a
mixed plexiform and stulous type, it can vary between 23 and 41%.
Pure stulous nidi need concentrations of 41% and above, depending
on the catheter position and ow characteristics
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Fig. 30.18 Sagittal and axial
sections of a blood vessel
showing the patterns of ow.
Blood ows as a parabolic
head in the vessel. Towards
the edges, due to the friction
with the endothelial lining,
the velocities are much
slower, and towards the
centre, the reduced friction
between the hypothetical
cylinders of blood creates a
faster laminar ow
Fig. 30.19 Effect of catheter
positions on the ow within
the AVM nidus. These are
used to one’s advantage
during different stages of
embolization
R. Kumar et al.
Case 3
A 34-year-old male patient presented with a sudden onset of
altered consciousness and hemiplegia. MRI was done which
showed a vascular malformation with an intranidal aneurysm. DSA done showed a choroidal AVM which is a subpallial AVM.The supply was exclusively through the anterior
choroidal artery, and the drainage was into the basal vein
(Figs.30.27, 30.28, 30.29, and 30.30).
Case 4
A 40-year-old male presented with a subarachnoid haemorrhage and a ruptured parietal AVM was found on cerebral
DSA. The patient was taken for curative embolization under
general anaesthesia.
The initial cerebral DSA was done via the snuff box
access (distal radial access), and radial access was used for
the intervention itself. More of our cases are being done via
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Fig. 30.20 Complete angiographic exclusion of the AVM nidus after
injections of NBCA into various compartments. By virtue of the intercompartmental communications, the supply from the PCA was
occluded without any catheterization of embolization. The upper
the transradial access. Our understanding of AVM
embolization is that using the ow itself to direct the embolizing agent into the nidus might give better results. Hence,
we rarely use bigger catheters such as 0.088 inner diameter
to get close to the nidus. A majority of our embolization
cases are done with 4F or 5F diagnostic catheters as the main
guide. When we switch to the radial access, it becomes much
easier when using the guides with a maximum ID of 0.070 or
6F guide catheters. We have also started using 125cm Sim
Select catheters and other 125cm diagnostic select catheters
to advance high up into the ICA for better support and to
maintain the ow for better embolysate percolation.
images are pre-embolization, and the lower ones are post-embolization.
The glue cast showing the nidal characteristics, the loopy vessels, the
spiral intranidal vessels, and the collector veins are seen in the nidal cast
(Fig.30.11)
Discussing further the merits, demerits, and many advantages
of radial access for endovascular treatments is beyond the
scope of this chapter.
In this patient, done early during our switch to transradial
access, a 6F radial sheath was used to gain access to the
radial artery and a 6F Fubuki Guide over a 5F cordis
Bernstein was used to access the bovine arch origin left
ICA.The Fubuki Guide was taken up all the way into the
high cervical ICA, and a Marathon ow-directed microcatheter was used to navigate close to the nidus. Onyx 18 was
used as the liquid embolizing agent to continuously and
completely ll the AVM nidus (Fig.30.31).
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Fig. 30.21 3D rotational angiography with VR reconstruction of the AVM showing the structure of the nidus as well as the various nidal characteristics including the intranidal aneurysm. However, the feeding arterial branches are not seen very clearly
Fig. 30.22 Catheter cone beam CT angiographic reconstruction of the
AVM showing the structure of the nidus as well as the various nidal
characteristics, including the intranidal aneurysm. In these images, the
feeding arterial branches are seen very clearly. They are very small
twigs. Once they are identied, embolization can proceed
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Fig. 30.23 Catheter cone beam CT angiographic reconstruction of the AVM with colour coding of the vascular tree and labelling of the
anatomy
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Fig. 30.24 The
conceptualization of an AVM
after the CBCT exploration
that is kept in mind during all
stages of the embolization
R. Kumar et al.
Fig. 30.25 Post-embolization 3D RA VR reconstruction showing the glue cast in the AVM, and the subtracted images showing complete occlusion with reservation of the arterial tree
30 Endovascular Approach forCurative Embolization ofBrain AVMs: Insights fromAngio-architectonics andAngio-anatomy
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Fig. 30.26 Post-embolization analysis of the glue cast on 3D RA as well as regular CT scan. The parallelism between the nidus and the cast has
to be demonstrated in order to achieve a complete and long-lasting cure
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