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7Dural Arteriovenous Shunts442
Fig. 7.29A–F. A 14-year-old boy with
superior sagittal sinus lesion. Note the
aneurysms on the middle meningeal artery
(A, B); the cavernous capture ensures a
satisfactory alternate drainage to the brain
veins (C, D). There are some remote,induced
cortical AVSs bilaterally (E, F)
443Infantile Dural Arteriovenous Shunts (AVS)
Fig. 7.30A–F. Legend see p. 444
enough information, particularly in infants in whom white matter maturation needs to be assessed and followed. The patency of the jugular
bulbs and sinuses can be well demonstrated.Angiography is currently the
only way to explore these lesions and to collect the necessary diagnostic
and prognostic information for treatment planning. Incomplete surgery
and neck or remote ligations have deleterious effects (Fig. 7.30). The
scores presented in Chap.2 of this volume are applicable to this pathology.The natural history of these lesions is consistently poor in our experience, with few cases of survival at young adult age despite repeated
embolization sessions.
7.5 Adult Type of Dural Arteriovenous Shunts in Children
The adult type of dural AVSs in children tends to develop within the sinus
wall or the ventral epidural space (Table 7.9).Of the possible causative triggers, thrombosis is certainly the one most clearly recognized. Trauma of
various origins may also create secondary dural shunts that are obviously
different from the traumatic injuries leading to an AVF (see Chap.16, this
volume). We already referred to the shunts remote from the area of direct
trauma or at a distance from a surgical field in cases of postoperative
DAVSs.With this type of etiology,the time elapsed between the trauma and
the diagnosis of the dural shunt can be as long as several years.These posttraumatic or postsurgical lesions are notably different from those described with the infantile type of DAVSs.The latter show an unsuppressed
persistent angiogenic activity, whereas the former are a focal angiogenic
wound healing phenomenon.This so-called adult type of DAVS may be encountered in young children. Several cases of neonatal cavernous plexus
fistulas have been reported with successful embolization with Gelfoam
(absorbable gelatin sponge;Ahn 1983) or coils (Konishi et al.1990) or even
with spontaneous regression (Vinuela et al. 1984; Yamamoto et al. 1995).
Although these lesions are managed in a similar fashion to the adult lesions,the treatment should be as conservative as possible.
7Dural Arteriovenous Shunts444
Fig. 7.30A–G. A 7-year-old girl presented with cervical
pulsatile mass in relation to a dilated jugular vein. Mild
headaches were noted at that time.Arterial and venous
ligations are done at the neck level. Three years later,
she was referred to us with macrocrania at 4 standard
deviations. The skull base lesion was transformed as was
its drainage, both retrograde with pial reflux and extracranial bypassing the ligation via the inferior petrosal
sinus (A–C).Progressive exclusion of the reflux by venous
disconnections and arterial embolization made it possible
to fill the sigmoid sinus stump with coils (D–G)
The long-term follow-up of DAVS treated with sacrifice of sinuses has
shown that, in some cases, a new DAVS develops in a previously normal
region. It is therefore strongly recommended to avoid the sacrifice of a
sinus that is still patent for the purpose of treatment of a dural lesion that
does not present any neurological danger for the child. Post-thrombotic
changes determine the possible risk for neurological symptoms; this is a
rare transformation in adults and has never been seen in children for
this type of DAVS.It is suggested that they are secondary to endovascular
treatment, as demonstrated in adults (Satomi et al. 2002). The favorable
spontaneous thrombotic occurrence of the shunt itself in the adult type
of DAVS seems to be a classic phenomenon. The symptoms in children are probably more rapidly eloquent than in adults, where the progression has been silent for a long time. In the pediatric population, sigmoid sinus DAVSs are rare; cavernous sinus sites are the most frequently
reported, and multifocality has not been described (Figs. 7.4, 7.31). Extrasinusal DAVS (dural-subdural, osteodural) have not been encountered.
The presence of an intracranial bruit is rarely spontaneously mentioned by the child, despite the fistulous nature of the disease. The frequency of cavernous sinus lesions draining anteriorly may not even cause
an objective bruit. A subjective complaint of bruit would certainly confirm the recent character of its change (or occurrence). Difficulties
at school are sometimes the only symptom that allows us to trace the
onset of the acoustic interference. The presence of a bruit and the CT
or MRI evidence of the lesion establishes the diagnosis, but they are
not sufficient to provide all the necessary pretherapeutic information;
445Adult Type of Dural Arteriovenous Shunt in Children
Ta ble 7.9. Dural sinus malformations and arteriovenous shunts
Dural sinus
malformations Infantile type Adult type
Prognosis PoorPoor Often excellent
High flow, high velocity + +++ –
Sinus thrombosis +++ + + (Psychiatric
(induced or spontaneous) manifestations)
Hydrodynamic disorders ++ (Macrocrania) ++ (Macrocrania) ± (Papilledema)
Neurological symptoms + (Pial congestion) + (Pial congestion) + (If pial reflux)
Bruit Incidental + ±
Sinus pouches ++ + –
Induced pial AV shunts – + –
Tr ansdural (pial) supply – ++ + (With thrombosis)
Multifocal dural lesions – ++ + (Poorer prognosis)
Intracranial hemorrhage + (Venous infarction + (If sinus occlusion + (If pial reflux)
without pial reflux) and pial reflux hemorrhagic venous infarcts
Seizures – + (Calcifications) + (If pial reflux)
Bone thickening – + (If sinus thrombosis) –
+++, Very f req uen t; ++, frequent; +, possible; –, not seen.
in particular, the cerebral venous drainage must be thoroughly analyzed,
which requires angiographic assessment. Most of the feeders can be predicted, but the development of potential alternative pathways should be
demonstrated and their compliance evaluated. Angiography is still the
only way to assess the information needed for proper treatment planning.
7Dural Arteriovenous Shunts446
Fig. 7.31A–D. A 4-year-old boy presenting with a spontaneous mid-cranial fossa
fistula involving the middle meningeal artery and draining into the ipsilateral ophthalmic vein (A). Clinical manifestations were those of the usual type of cavernous
sinus draining lesion with exophthalmos and cranial nerve palsy. B Embolization was
performed in the same session. C, D Diagnostic angiography was performed and
complete occlusion of the lesion was obtained. Following embolization, after 3years
of follow-up, the initial symptoms have completely disappeared
7.6 Other Dural Shunts
In this section we have regrouped diseases as well as the normal responses of the meninges as a differential type of diagnosis,but also to illustrate
the variety of triggers that can create dural AV shunts. Careful analysis
will assist in differentiating between the transdural resupply to normal
brain, clot colonization with angiogenesis, and the dural location of general disorders.
7.6.1 Vein of Galen Aneurysmal Malformation
Dural shunts have been seen in four different instances in children presenting with VGAM:
1. Following thrombosis of the sigmoid sinuses upstream from a jugular
bulb occlusion (Fig. 3.53)
2. Following a direct, surgical, incomplete approach to the VGAM
3. In premature babies with severe arterial occlusion of the cerebral arteries
4. Remote from the lesion, transiently in the superior sagittal sinus
(Fig. 3.53)
Although they complicate the angioarchitecture of the VGAM disease,
they are in fact not disease-related, but correspond to a predictable response by the sinus wall or meningeal arteries to certain specific triggers.
Blood clot represents a stimulus to angiogenesis, and cerebral ischemia is
also an active trigger to the development of these DAVS (see Chaps. 3–5,
this volume). Surgery is an additional factor that may induce some of
these responses. These shunts are asymptomatic, and many of them are
actually vascular compensating mechanisms; they need to be preserved
and should not be treated. We have not observed direct dural supply to
the venous pouch in a genuine VGAM; however, enlargement of dural
arteries at the falx–tentorial junction can be identified in some children,
indicating the effect of high flow over time, as in any dural sinus.
The dural involvement described above in VGAM is different from the
vein of Galen DAVS described by Fournier et al. (1991). Clearly, this
significant difference points to the nature of the two veins involved: the
medial vein of the prosencephalon (choroidal collector vein bringing the
plexus to the primitive sinus across the subarachnoid space) and the true
vein of Galen (a dural sinus bulging into the subarachnoid space to collect cerebral venous blood). Classifying a VGAM as a DAVS is therefore
erroneous.
7.6.2 Dural Supply to Pial Cerebral Arteriovenous Malformations
In CAVMs, dural communication can occur in children. This feature is
part of the arterial angiopathy response of late development compared to
the venous response.Three situations can create dural contribution to the
CAVM or to the adjacent brain, and sometimes to both (see Chap. 5, this
volume).
447Dural Supply to Pial Cerebral Arteriovenous Malformations
1. Thrombosis may give rise to dural or transdural supply and eventually
AV s h u nt i n g . It should be remembered that, with the exception of the
true vein of Galen, no intradural vein has vasa vasorum. Therefore,
only associated sinus thrombosis or vein of Galen dilatation can give
rise to an intraluminal angiogenesis draining into the remaining
patent portion of the otherwise thrombosed channel.
2. In the pial vasculature, high-flow angiopathy is known to produce adventitial angiogenesis.This is different again from the previous DAVSs
associated with CAVMs. However, the transdural supply to CAVM directly and/or to the adjacent cerebral arteries certainly requires this
adventitial angiogenesis. Local ischemia and superficial bleeding
episodes are well-known triggering factors for such a dural contribution.
3. Surgery to the lesion or removal of a hematoma establishes pathways
for new vessels across meningeal compartments. Cutaneous supply
through burr holes is frequently seen in older patients with CAVMs.
However, there is rarely supply to the brain associated with previous
ventricular shunting. Since the burr holes in this situation are remote
from the CAVM location, local effects of the surgical angiogenic triggers and the specific sensitivity of the CAVM region to such stimulation can be postulated.
7.6.3 Proliferative Angiopathic Disease
Dural contribution in proliferative groups of angiopathy can be spectacular. It corresponds to an alternative supply and should be preserved as
such.Surgical approaches to proliferative angiopathy and moyamoya disease tend to use the same capacity of the dural arterial network to take on
the supply of the incapacitated cerebral vasculature.It is difficult to know
in these cases whether this response is the result of the normal explosive
angiogenic factors of the disease itself or the normal response to a particular trigger.What looks like a disease in fact preserves neurological function and makes therapeutic decisions difficult. We believe that it corresponds to an uncontrolled response to a nonproportional ischemic trigger (see Chap. 18,this volume).
7.6.4 Systemic Disorders
Several systemic diseases are known to give rise to various types of AVS
in adults. These findings are exceptional in young children, in particular
at the dural level. Large vessels are likely to be involved in these sites
rather than meningeal arteries. Single-hole multifocal AVFs in HHT
(hereditary hemorrhagic telangiectasia or Rendu-Osler-Weber) disease
and vertebro-vertebral fistulas have been reported in children and young
adults.Multifocal CAVMs in neurofibromatosis-1 (NF1) can also be seen.
7Dural Arteriovenous Shunts448
7.6.5 Recurrence in Intradural AVS and Secondary Transdural Supply
Incomplete and proximal embolization triggers angiectasia and regional
collateral circulation. It may end up creating an area of shunting larger
than the primary nidus if in addition some degree of local ischemia has
resulted from the proximal occlusion.
The greater the iatrogenic ischemia, either direct or secondary to a
blood flow rerouting after embolization, the higher the chances of producing a transdural contribution. However, this transdural supply has to
be understood as the normal response to an abnormal demand. It may
look poorly adapted, with direct contribution in the area of the shunt or
remote in a healthy region.
Any intravascular clotting or extravascular blood triggers angiogenesis
as a normal response aiming to digest the blood products.Yet in some instances,this phenomenon escapes control and seems to remain rather than
being transient. There are probably situations where inflammatory reactions induced by emboli (or other foreign bodies) may further trigger this
cascade (Figs. 4.13, 5.13,5.22,7.32).Such changes must correspond to a distorted recruitment or response of the angiogenic capacities in relation to
the vascular malformation as the source of abnormal signals. The focal,local, or regional characteristics of the response as well as its duration are unpredictable; they seem more exaggerated in children than in adults.The recruitment of the AVM draining vein for the recurrence (whether hemorrhage or intervention) confirms the focal character of the phenomenon
and the persistence of the lesion rather than a hyperemic scarring reaction.
As most AVMs do reveal, they go through an angiogenic phase at this
time– unrepressed, unnecessary abnormal production– yet this event is
self-limiting in time, since a nidus does not grow except in the situations
mentioned above and with high-flow angiopathic changes (Chap. 5, this
volume). It seems that the older (on an embryological time scale) the
causative event,the higher the chances of seeing new AVMs appear or an
AVM nidus expand as in CAMS (Figs. 6.13, 6.15); full involvement of a
given cephalic segment may express over 28 years (Fig. 6.7).
From empirical observations,such angiogenic responses are linked to
the arterial capillary side and will be encountered in special lesions such
as PHACE,proliferative angiopathy,CAMS and some special conventional AVMs (Table6.3) (Scheme 6.1). Such observations further support the
fact that hemodynamics generate multiple signals and triggers to complex biological cascades and homeostatic systems. The concept of compliance of the host to an AVM (that we introduced nearly 20 years ago) as
the key factor to anticipate the natural history and response to treatment
is still valid. AVM approaches (classifications, hemodynamics, etc.)
should not be overestimated in comparison to host parameters to overcome the effects of the malformation considered as a biological disease
(abnormal signal emission).
A special type of recurrence is related to the vein of Galen structure: the
only intradural vein to have vasa vasorum. This feature can lead to a very
particular type of post-therapeutic recurrence remote from the site of the
initial AVM. This event has not been observed again; it combined several
regional triggers to a partially clotted ectatic vein of Galen (Fig. 7.32).
449Recurrence in Intradural AVS and Secondary Transdural Supply
7Dural Arteriovenous Shunts450
Fig. 7.32A–F. Legend see p. 451
7.7 General Remarks on Treatment
The diagnosis of a DAVS in a child leads to different diagnostic and treatment strategies depending on the age and type of lesion involved. Some
general precautions should be kept in mind.In neonates,invasive studies
are warranted when therapeutic management is urgently required.Multiple noninvasive examinations are often unnecessary for the proper decision-making process.
At all ages, primary assessment of the situation is best achieved by
good clinical examination and high-quality MRI. Proper visualization of
the skull base should be obtained (including sagittal, coronal, and axial
imaging) to demonstrate the posterior fossa venous outlets. It is only in
exceptional cases that MRI and clinical information does not enable us to
make the diagnosis of DAVS in the pediatric population. Angiography is
a pretherapeutic examination. The place that Doppler ultrasound and
endoluminal hemodynamic monitoring may have in the management of
these lesions has not yet been clarified. The immediate prognosis is not
related to flow characteristics, and treatment evaluation and follow-up
cannot reliably depend on results of flow studies. Follow-up evaluation
will,therefore, be based on MRI (with contrast enhancement) and less
often angiography aiming to evaluate the venous drainage of the growing
brain.
The goal of treatment in each type of DAVS is difficult to establish, as
patency of the sinuses must be preserved in most cases, since their
thrombosis can produce extensive venous cerebral infarction. Transarterial embolization is, in our experience, the optimal approach to these
lesions. The use of liquid agents such as N-butyl cyanoacrylate (NBCA)
constitutes the only guarantee that partial or complete occlusion will remain stable. The recanalization observed with other agents is unacceptable in such children, for whom the therapeutic window for intervention
is short. In addition, recanalization in children is sometimes more difficult to manage than the primary architecture.Arterial coils tend to produce proximal occlusion and collateral circulation that is often unreachable, necessitating secondary complex and hazardous management. An
attempt to be definitive is particularly crucial in this group of diseases,
and careful diagnosis and treatment planning is essential. Partial targeted treatment can be proposed in order to remove the risk of focal brain
damage using a transarterial or transvenous approach to close the pial
venous reflux (coil occlusion of the Labbé vein opening into the sigmoid
sinus or in the straight sinus to stop reflux into the area) (Figs. 7.22,7.31).
This type of venous rearrangement must be preceded to some extent by
AV S reduction by arterial embolization.
451General Remarks on Treatment
Fig. 7.32A–F. Cerebellar AVM (A, B) cured by embolization and surgery. The follow-
up angiogram 6 months later showed a newly developed AV shunt in the lumen of the
partially thrombosed vein of Galen (C–E). Retrograde catheterization of the vein of
Galen allowed the placement of a few coils and promoted complete exclusion of the
shunting zone (F)
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