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The signs of water retention start with macrocrania without ventriculomegaly. Clinical consequences are almost consistently neurocognitive
delay with no direct relationship to the degree of the increase in head circumference.The link between the water disorders and the myelinization
delay is of interest, but still speculative. With regard to the presence of
macrocrania with an increase in intracranial pressure,it is thought not to
be an indicator of negative outcome in infants with intracranial shunts,
unless a DSM is diagnosed (see Chap. 7, this volume). If left untreated,
this water dysfunction progressively leads to ventriculomegaly. In other
situations when the suture enlargement is too slow or not possible, signs
of transependymal resorption become evident. The loss of a functioning
resorption gradient is then established, and true hydrocephalic manifestations will occur.Ventricular shunting at this time is associated with significant morbidity (see Chap. 3, this volume). This morbidity demonstrates a widespread lack of understanding of the physiology of the water
equilibrium in infants and the various and progressive shifts that result in
a very unstable situation.
Ve nous changes have a direct impact at this age. Direct pial or subarachnoid congestion is noted in CAVMs,whereas they remain absent for
a long time in VGAMs. In non-Galenic AVMs, local congestion rapidly
leads to focal ischemia,as revealed by convulsions and later hemorrhage.
Rarely do such infants present with progressive deficit, except for deep
thalamic or basal ganglia lesions,which may be part of CAMS (cerebrofacial arteriovenous metameric syndrome). Recurrent and multifocal
postischemic venous hemorrhagic infarcts in these CAVM patients are
often remote from the AVM site.In VGAM,pial congestion is absent for a
long time and depends on whether maturation of the venous drainage at
61Infancy
Fig. 2.22. A Neonatal chest X-ray and B CT in a female neonate weighing 2,650 g and
presenting with severe multiorgan failure and cerebral encephalomalacia.The neonatal score was 6.She died 24 h later
the skull base occurs (cavernous sinus capture; see Chap. 3,this volume).
The dysmaturation and subsequent closure of the jugular foramen in
VGAMs and in some CAVMs and in DSM patients is unlikely to be related to a high-flow venous angiopathy, and more likely to cause impaired
postnatal development. The dominant vault enlargement in these children with macrocrania probably shows the usual active enlargement of
the skull base caused by the growing brain; in addition, the specific
growth patterns of the posterior fossa make it impossible for the jugular
foramen to develop harmoniously. Regardless of the etiology involved,
the restriction of cranial venous outlets produces retrograde diffuse venous congestion. A direct relationship between the demonstrated reflux
and the cerebral damage then occurs. The deeper or more midline the
retrograde congestion is expressed, the more diffuse the infarctions and
hemorrhages. These rather acute or subacute failures can be expected in
most cases. The slowly developing end result of hydrovenous dysfunction
at the posterior fossa level will be progressive tonsillar prolapse (see
Sect. 2.5.2). Its presence is an expression of the stage of the disorder
rather than any specific etiology.We have encountered tonsillar prolapse
every time that the above conditions were in effect.If such conditions are
met in non-AV diseases, it is likely that the same response would occur.
This prolapse is reversible for a long time with adequate treatment of the
AV shunt, even in the presence of jugular bulb occlusion.
As soon as this phase has passed or the prodromes of each situation
have been identified and corrected, the evolution will be slower and
with less rapid cerebral consequences. However, brain damage that has
occurred in the meantime is less likely to be reversible and the outcome
result is one of increased morbidity associated with decreased mortality.
This supports the concept of a therapeutic window for intervention at the
optimal moment, thereby permitting treatment to result in a normally
developing child. MRI, which enables one to assess the brain tissue, the
subarachnoid spaces, ventricular size, and the position of the tonsils, in
combination with the head circumference and neurocognitive testing,
provides the best information for follow-up. Stagnation of the head circumference or rapid closure of the sutures results in a disastrous situation and reveals the loss of brain substance through its incapacity to
enlarge the skull by craniofugal pressure; melting-brain syndrome often
follows such a phase, again indicating the vulnerability of the cerebral
tissue at this age.
2.4.4 After 2 Years
Children that have not presented with systemic and hydrovenous disorders will reveal their vascular lesions with neurological symptoms. Cardiac failure does not occur for the first time at this age. Hydrodynamic
disorders that were not present before and appear now are caused by mechanical compression of the intraventricular foramen or the foramen of
Magendie. Direct compression of the mesencephalic aqueduct, although
well known, is in fact extremely rare even in VGAM.Venous thrombosis
may start to occur as part of the high-flow angiopathy phenomena (see
2Introduction and General Comments Regarding Pediatric Intracranial Arteriovenous Shunts62
Frequency of Vascular Lesions
Per Age Group
Infants
1. Aneurysmal malformation
of the vein of Galen
2. Dural sinus malformation
3. Pial arteriovenous shunt
4. Cavernoma
5. Arterial aneurysm
Frequency of Vascular Lesions
Per Age Group
Children
1. Pial arteriovenous
malformation
2. Cavernoma
3. Arterial aneurysm
4. Dural arteriovenous shunt
(juvenile type)
Chaps. 5,6, this volume).During the follow-up of children, very different
issues are recognized. In particular, the hemorrhagic risks are more frequently discussed. Our experience clearly shows that, in the pediatric
population during the first 2years of life, physiological, anatomic, and
pathophysiological considerations differ from those in older children.
The endovascular technical discussions are trivial considerations when
compared with these ongoing changes. At age 3–10years, these challenges are easier to deal with, and after the age of 10,lesion management
requires a more classical knowledge of lesion risk vs treatment risk and
feasibility vs patient acceptance. The relationship with the patient
changes significantly at this point, and this should never be underestimated, since it often constitutes a particular source of difficulties in the
decision-making process at this age. The clinical interaction with young
children and adolescents will be particularly challenging and entirely different from those in adults; information to parents also requires thorough knowledge of the consequences of the diseases involved rather than
the techniques available.
2.5 Classification by Symptom Group
Systemic manifestations, hydrovenous disorders with tonsillar prolapse,
and the melting-brain syndromes are the most typical manifestations of
CVAM in young children.
2.5.1 Congestive Cardiac Manifestations
High-output cardiac manifestations are the most frequent systemic manifestation encountered. Liver and renal insufficiency occurs secondary
to congestive cardiac failure (CCF). Their extent should be carefully assessed in neonates before the therapeutic decision is made (see neonatal
score in Sect. 2.6).
Cerebral AV shunts are infrequent causes of CCF.When CCF is suspected following clinical examination including cranial auscultation, then
confirmation can easily be obtained by transfontanel ultrasound (Pellegrino et al. 1987). Unfortunately, many of these infants are initially considered to have congenital heart disease (Cumming 1980; Long et al.1974;
Massey et al; 1982) and are sometimes subjected to cardiac catheterization (Long et al; 1974; Massey et al. 1982; Pellegrino et al. 1987). Cardiac
manifestations secondary to intracranial cerebral AV shunts are extremely variable in extent and vary from severe heart failure with multiorgan
failure resistant to medical treatment,to well-tolerated mild cardiac overload or incidental discovery of an enlarged cardiac silhouette. In the past,
the prognosis of a newborn presenting with severe heart failure from a
CAV shunt was poor, with a mortality rate of 100% (Hoffman et al. 1982;
Johnston et al. 1987). However, in recent years, the use of endovascular
therapy in newborns and infants has significantly changed this traditionally poor outcome in these patients (Garcia Monaco 1991a).Arterial embolization, although technically challenging in babies weighing only a
63Congestive Cardiac Manifestations
Intracranial AV Shunt
in Children
Symptom Groups
Systemic manifestations
Hydrodynamic manifestations
Cerebral manifestations
Intracranial AV Shunt
in Children
In Utero Manifestations
Cardiac overload
Congestive cardiac
failure (cp>200/mn,
ventricular extrasystoles,
tricuspid insufficiency)
Macrocrania
Vent ricu lomegaly
Brain loss
few kilograms, can result in dramatic improvement of cardiac function
(see Chaps. 3, 4). Among 600 referred cases (adults and children) with
cerebrocranial vascular lesions, only 30 (5%) presented with cardiac
symptoms (Garcia Monaco 1991a). However, when only the pediatric
population was considered, this figure rose to 19%. Some types of isolated high-flow fistulas in children are surprisingly infrequently associated
with cardiac manifestations (see Chap.4). VGAMs, in contrast, are frequently associated with cardiac manifestations. They account for 73% of
the population with CCF or cardiomegaly of cranial cause (Garcia Monaco 1991a). Cardiac angiography is not indicated and may result in transient or permanent impairment of the femoral vasculature. The cardiac
manifestations are not specific in suggesting a cranial cause,but occur in
the presence of right-to-left shunt, an atrial communication or patent
ductus arteriosus (Cumming 1980; Maheut et al. 1987; Pellegrino et al.
1987), or ventricular septal defects. This persistence of a fetal type of circulation should not be regarded as a true cardiac anomaly, since it reflects
right atrium volume and pressure overload. In Garcia Monaco’s series,
severe heart failure in newborns was always secondary to an intracranial
vascular lesion.However,in some instances management of a patent ductus arteriosus may have to be considered (Chevret 2002) prior to active
treatment of the intracranial shunt itself. Besides VGAM, cerebral or
dural AV shunts can also result in severe CCF (Chan and Weeks 1988;
Albright et al. 1983).In addition, CAV shunts produce cardiac failure only at a very young age (1–19 days in Garcia Monaco’s series). The older the
child, the lower the chances are of cardiac manifestations and the milder
they will be. Mild heart failure or simple cardiomegaly is observed in
infants whose chief complaints are macrocrania or other neurological
manifestations.In these cases, the etiologic diagnosis occurs later, usually after 6 months of age. The prognosis of severe CCF of cranial origin in
newborns or infants has traditionally been considered to be very poor,
but this has improved significantly with modern endovascular techniques.Treatment of CCF with giant capillary hemangiomas of the face is
different. Symptoms start with the proliferation phase of the lesion at
4–12 months of age. The objective here is to exclude the lesion from the
general circulation and to gain time to allow spontaneous regression to
occur (see Chap. 11, this volume).
2.5.2 Hydrodynamic Disorders
A special relation between cerebral veins and water absorption has been
suspected for a long time:
The hypothesis that cerebrospinal fluid is absorbed by the Pacchionian granulations is instantly shattered by the fact that these structures only develop in time.
They do not exist in infants and young children, nor do they exist in many animals.
(Dandy 1929)
According to Le Gros Clark (1920) and Gomez et al.(1981), changes leading to the development of arachnoid villi and granulations are confined
to the posterior half of the superior sagittal sinus; lacunas are present
2Introduction and General Comments Regarding Pediatric Intracranial Arteriovenous Shunts64
Intracranial AV Shunt
in Children
Systemic Manifestations
Cardiac failure
Pulmonary hypertension
Renal dysfunction
Hepatic insufficiency
Coagulation disorders
Intracranial AV Shunt
in Children
Hydrodynamic Manifestations
Macrocrania
Vent ricu lomegaly
Hydrocephaly
Tonsillar prolapse
Melting brain syndrome
Hydromyelia
during the 26th week, and by the 35th week typical arachnoid villi are
seen. These increase in size and complexity during childhood. The first
appearance of complex proliferations has been reported by the
18th month. However,both contributions do not provide information on
the function of the developing arachnoid villi and granulations.
More recently,Welch and Friedman described the flow patterns
through the labyrinth of small tubes in monkey villi: the tubes are closed
by high pressure in the venous sinus and opened by high CSF pressure.
However, the CSF flow through human arachnoid granulations may not
be as responsive to venous sinus pressure as in the animal villi (Upton
and Weller 1985) The various steps and the schedule of this maturation
are poorly understood. Only a few facts seem established or accepted,
e.g.,the development of the villi is not mechanically related to the formation of the subarachnoid space.Villi have been described in the lungs of
South American Indians living at a high altitude; the presence of the villi
was related to the permanent edema present in the interstitial tissue. The
growth of the villi is linked to the superior sagittal sinus (SSS) development.For a long time,evidence of villi could only be found along the posterior half of the SSS. Although visible at neonatal and infant ages, villi
and granulations do not show full complex development until infancy or
early childhood.
Although factors of functional maturation are unknown,relationships
can be postulated between villi function and venous hemodynamics. The
venous system continues developing during the first few months of life,
and this venous hemodynamic maturation may play a significant role in
villi development.In normal situations,specific features of cranial venosinus flow include pulsatility,negative pressure (sump effect), and absence
of valves.In babies,Valsalva episodes are more frequent,which primarily
increases venous pressure, but also suppresses the diastolic flow in the
arteries to the brain. These observations led to the belief that most of the
cerebral blood flow is, to a significant extent, sumped by the venous system rather than pushed as in any other part of the body (with the possible exception of the lungs). In abnormal conditions such as high-flow AV
shunts,the sinusal negative pressure is diminished. The arterial steal phenomenon,noted in some rare cases, is associated with the disappearance
of the arterial diastolic flow. If these changes are sufficient to create the
link between villi and sinuses and their progressive postnatal maturation,then the question remains of where the water is reabsorbed in the
meantime (Scheme 2.9). Again, certain facts should be recalled: (a) the
lack of ependymal resistance to free exchange between the fluid in the
extracellular space (ECS) and the CSF, and (b) the similar composition of
ECS and CSF may have a direct bearing on the possibility that the
parenchyma is the main source of nonchoroidal CSF formation responsible for up to 10%–20% of CSF production (McComb 1983).
Since the venular endothelium is comparable to that of the capillary
bed, the venular endothelial cells possess a comparable polarity and perhaps participate in the active regulation of the ECS and CSF environment. It has been suggested that the intraparenchymal vasculature is
directly linked to the sequestration and removal of substances moving in
and between the CSF and the ECS. Such a vascular uptake of CSF sub-
65Hydrodynamic Disorders
stances may have a significant role in the absorption of CSF and the
maintenance of a homeostatic environment (Povlishock and Levine
1984).
From our experience in vascular disorders in neonates and infants,we
believe that, both normally and in the presence of an intracranial AV
shunt,the intrinsic and CSF fluids are mainly reabsorbed into medullary
veins of the brain and cerebellum. As soon as the conditions are met to
recruit villi functions, a progressive shift will take place, separating the
intrinsic system and the extrinsic types of resorption. Since all cerebral
veins open into the torcula at birth, the system is obviously convergent
and therefore poorly compliant in the case of early intracranial AV shunt;
normal secondary capture of the middle cerebral veins by the cavernous
sinus is the earliest diverging opportunity for venous drainage of the
brain. Ophthalmic and facial veins as well as the pterygoid plexuses may
become important associated venous (and water) pathways,despite their
different hemodynamic regimen in the facial and external jugular veins.
In high-flow AV shunts draining into the torcula, the facial veins have a
comparatively lower pressure than the SSS; pulmonary hypertension,
maturation of fetal circulation,and progressive skull base growth will all
further increase the positive pressure changes in the sinuses. We therefore accept the observations that hydrodynamic disorders are usually
absent in neonates and develop after a free interval in infants. Later on,
the fusion of the sutures will contribute further to the advent of a poorly
2Introduction and General Comments Regarding Pediatric Intracranial Arteriovenous Shunts66
Scheme 2.9. Cranial
hydrodynamic circuits.
CSF, cerebrospinal fluid
compliant hydrovenous system, in particular when the villi have not become functional. Diploic engorgement and bone thickening (Figs. 2.23)
are associated with this search for collateral circulation into the subgaleal
veins and cranial lymphatics (Scheme 2.10).
The sequence of hydrodynamic impairment events may occur as follows in intracranial AV shunts: a stabilized shift in hydrovenous function
with abnormal parameters creates macrocrania.A ventriculocortical gradient allows reabsorption of the secreted water as well as some transmeningeal passage in the dural venous network present at that age.Progressive failure in the medullary venous system, worsened by jugular
stenosis that progressively accompanies the macrocrania,produces a loss
in the ventriculocortical gradient and causes ventricular enlargement,
hydrocephalus with raised intracranial pressure (ICP). Subependymal
atrophy(with normal ICP) resulting in slowly progressive ventriculomegaly represents a different effect of the same constraints and failure.
67Hydrodynamic Disorders
Fig. 2.23. A 12-year-old boy
presented with a vein of Galen
dilation due to a choroid plexus
arteriovenous lesion.Following
chronic venous sinus congestion,note the significant
enlargement of the cranial
bones
Scheme 2.10. Events likely to
interfere with the hydrovenous
maturation process
It points to the trophic role of the hydrovenous equilibrium in the interstitial space. At the hydrocephalic stage, ventricular shunting will reverse
the necessary ventriculocortical gradient without treating the cause and
often leaves residual ventriculomegaly through subependymal atrophy.
Rapid disequilibrium provoked by the ventricular shunting may sometimes lead to slit ventricles (Fig. 2.24). These facts and speculative
remarks derived from our experience require special comments for the
posterior fossa.
In intracranial AV shunts in neonates and infants, the usual posterior
fossa drainage takes place through the petrosal vein and superior petrosal sinus toward the cavernous sinus or caudally to the jugular bulb or
2Introduction and General Comments Regarding Pediatric Intracranial Arteriovenous Shunts68
Fig. 2.24A–C. A female neonate
presented with cardiac failure.
A MRI performed at that time
shows the small vein of Galen
aneurysmal malformation.
At 5 months, following progressive macrocrania,the child was
shunted. She rapidly developed
neurological problems in
relation to a slit ventricle
syndrome. B, C MRI performed
at that time demonstrated the
rapid tonsillar prolapse with
the enlargement of all the
perimesencephalic and pontine
veins. D see p. 69
spinal cord veins (Scheme 2.11).Stenosis or thrombosis of the transverse,
sigmoid sinus, jugular bulb, or jugular vein will lead to venous reflux
into the cerebellar veins from the lateral sinuses or petrosal veins
(Scheme 2.12).If at this time the cavernous sinus is not sufficiently developed,then there is insufficient venous outflow pathways for the posterior
fossa, resulting in interference with the absorption of the cerebellar
water. Hence there is accumulation of intrinsic fluids, leading to an increase in posterior fossa water contents with resultant tonsillar prolapse
(Figs. 2.24–2.26).A normal or small fourth ventricle is noted.As the accumulation of brain water supratentorially results in macrocrania, the infratentorial venocongestive status depends on the available outlets and it
manifests itself as tonsillar prolapse.
To n sillar prolapse expresses the combined impact of all the posterior
fossa hydrodynamic disorders.It is primarily due to the particular physiology of CSF circulation in neonates and infants, but also the congestion
of the cerebellar veins into the sinuses (initially patent) and the stiffness
of the bony sutures.Secondarily,it is caused by the progressive occlusion
of the jugular foramen, which increases the congestion and further delays
granulation maturation. It is reversible through a decrease in the sinus
venous hyperpressure if the available outlets are sufficient (Fig. 2.27).
The fourth ventricle has a slit-like appearance rather than being small in
relation to a presumed aqueduct compression by an ectatic venous
pouch. Finally, caudal engorgement may involve the spinal ECS, leading
to longitudinal cavitation or atrophy (Fig. 2.28). Such a situation is encountered in all types of intracranial AV shunts,VGAM, pial AV shunts,
and DAV,provided that the appropriate sequence and timing of events are
given.
69Hydrodynamic Disorders
Fig. 2.24 (continued) D Emergency embolization resulted in
an almost complete occlusion of
the malformation, improvement
of the tonsillar prolapse, and a
decrease in the basal vein
network. Clinically,the child
improved significantly,but a
mild deficit remained following
the slit ventricle episode, as well
as some degree of mental
retardation.She is now 13 years
old and has a score of 1
2Introduction and General Comments Regarding Pediatric Intracranial Arteriovenous Shunts70
Scheme 2.11. (left) Neonatal cerebral venous drainage. At this age, venous drainage
converges into superior and posterior sinuses.Posterior fossa drainage is via the mesencephalic vein and the superior petrosal sinus to the cavernous sinus and caudally to
the jugular bulb. There is no cortical venous drainage to the cavernous sinus yet
(hatched).Arrows indicate pathway flow
Scheme 2.12. (right) Infant venous drainage and distal sigmoid venous occlusion (as-
terisk). With high pressure caused by the arteriovenous shunt in the sinus, flow of the
cortical vein is forward into the cavernous sinus.Flow is reversed in the temporal vein
as well as in the petrosal and cerebellar veins (hatched). Cavernous high flow via the
inferior petrosal sinus to the jugular bulb occurs,as well as via the ophthalmic vein or
the vein of the oval foramen. Posterior fossa drainage depends critically on the adequacy of the venous channel supratentorially, the cavernous sinus drainage, and the
presence of the patent jugular vein distal to the occluded bulb (double arrow).If there
is inadequate drainage,venous flow in the posterior fossa vein becomes stagnant and
enlarges the cervical spine veins caudally
Fig. 2.25A,B. A male neonate presented with mild cardiac failure. He was referred at
the age of 5 months,at which time he was found to have slight acquisition delay (score
of 2). MRI demonstrated single-hole high-flow fistula in the prefrontal branch of the
left middle cerebral artery.Note the moderate atrophy around the lesion and the tonsillar prolapse
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