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111Modern Concept of Vein of Galen Aneurysmal Malformation
Fig. 3.4A–D. Legend see p.112
3.4 Vein of Galen Aneurysmal Dilatation
Ve in of Galen aneurysmal dilatations (VGADs) (Figs. 3.5–3.7) belong to
the group of cerebral AVMs (CAVMs) draining into the deep venous system with an acquired ectatic dilatation of the vein of Galen confluence
due to either stenosis at the venodural junction or thrombosis of the
straight sinus. The dilated vein in this instance is the vein of Galen (great
cerebral vein): it drains the AVM as well as normal brain tissue.The presence of reflux into the normal cerebral venous tributaries that open into
the venous pouch indicates and confirms the presence of a matured
Galenic confluent, the diagnosis of VGAD, and definitively excludes the
3Vein of Galen Aneurysmal Malformation112
Fig. 3.4A–D. Neonatal specimen showing the choroidal type of VGAM opening into
the median vein of the prosencephalon and secondarily into a falcine sinus. Postmortem study was obtained (courtesy of Prof. Landrieu). The general pathology
showed no extracranial malformation. Neuropathological examination at autopsy
showed that the cranium was unusually thick and the fontanelles appeared ossified.
The brain weight was 220 g after fixation. There was a diffuse, symmetric atrophy of
the cerebral mantle, and the ventricles were markedly dilated. The ependyma was
thickened with the formation of numerous ependymal rosettes and astrocytic proliferation. The destruction of the cerebral mantle was either complete or characterized
by a multicystic degeneration of the cortical zone invaded by macrophages. In the
residual cortex,white matter,central grey nuclei, and subependymal zones, there were
multiple malacic lesions from various ages and types: recent hemorrhagic infarcts;
calcium deposits and incrustation of cellular process; nets of glial spumous cells; and
pseudo-crystalline lipidic deposits. The periphery of these malacic lesions was frequently underlined by a slight astrocytic reaction. Diffuse subpial hemorrhagic
necrosis and congestion of the subarachnoid vessels were prominent in the occipitotemporal areas, but vascular dilatation was also present,to a lesser extent,in all subarachnoid and parenchymal areas.The brain stem appeared malacic and edematous,
without cavitation or glial reaction. The cerebellum was largely preserved, but focal
depopulation of Purkinje cells and neurons of dentate nuclei is noticeable. The mesencephalic aqueduct appeared permeable, but could not be precisely measured. The
vascular malformation was situated in the tectal area, in close connection with the
posterior part of the circle of Willis. This malformation consisted of a large, entirely
extracerebral cluster of intermingled vessels, closely associated with formations of
mature choroid plexus. The small vessels displayed very irregular walls forming
valvule-like folds, the media and the intima showing considerable variations in thickness. There was an internal elastic membrane showing sharp interruptions in those
areas in which the dysplastic vessels shunt together or make shunts with venous-like
branchs ending in the dilated Galen vein. The vascular cluster was nourished, through
large shunts, by many arterial branches coming from the circle of Willis, especially
from choroidal arteries. These nourishing arteries also appeared dysplasic with irregular walls. The dilated vein of Galen, 30mm at its maximum diameter, was situated
posterior to the bulk of the vascular malformation.Its wall,500 mm thick, was made of
a thin intima and of thick fibrous adventice. Many vascular fistulas appeared at the
opening of the ampulla, in the lateral and anterior walls, measuring 200–500mm. The
dilated vein opened posteriorly into a patent falcorial sinus of normal histological
structure. Comments: (A) the vascular malformation is entirely extracerebral, appears as a dysplastic process affecting the arteriovenous differentiation of the small
choroidal vessels,resulting in the formation of numerous shunts,each of variable importance; (B) the hemodynamic and/or hydrodynamic consequences are largely prenatal, as shown by the pathology of the cerebral lesions
diagnosis of VGAM (Fig. 3.8). The evidence of primary opening of the
shunt in a nonchoroidal vein,even without reflux,confirms the diagnosis
of VAGD.
In neonates and infants,the occurrence ofVGAD is infrequent.However, 10 years ago 20% of children referred with the diagnosis of VGAM
were actually VGAD patients. Today this confusion is much less frequent.
VGADs are encountered in older children, corresponding in most cases
to a deep-seated CAVM; they may show all the symptoms associated
with this location and type of lesion. Tectal CAVM locations are those
most closely resembling VGAMs; however,the transmesencephalic arteries will be seen at the time of angiography to be projecting below the
P2 segment of the posterior cerebral artery, on the lateral projection
of the vertebral injection and easily seen on axial MRI sections.
113Ve in of Galen Aneurysmal Dilatation
Fig. 3.5. A Ty pi cal appearance
of vein of VGAM with the
choroidal supply to the dilated
median vein of the prosencephalon. B Ty pi cal appearance
of the choroidal supply to a
choroidal arteriovenous malformation (AVM) associated
with a dilated vein of Galen
and reflux in the deep vein
of the brain following straight
sinus thrombosis
Subependymal arteries can be seen in VGAD in certain choroid plexus
AVMs. Thalamoperforating arteries are also seen in VGADs of thalamic
AV M o r i g in. Proper analysis of the venous anatomy and clinical correlations will always enable one to differentiate the type of malformation involved.
Characteristic symptoms are progressive neurological deficits associated with the mass effect and/or retrograde venous congestion,
and hemorrhage of venous origin, either thalamic or subependymal.
Epilepsy and other cortical manifestations are rare. Although theoreti-
3Vein of Galen Aneurysmal Malformation114
Fig. 3.6A,B. False VGAM diagnosed at the age of 6 months in a young boy presenting
with a macrocrania. C Note the cingulate gyrus AVM draining into a posterior callosal vein and into a large vein of Galen
cally possible, cardiac and hydrodynamic disorders are also rare. It is
interesting to note that VGADs develop postnatally (no melting-brain
syndrome despite pial veins reflux, no mental retardation, no jugular
bulb dysmaturation), and lesions have usually already been present for
a long time by the time they are diagnosed (acquired venous thrombosis, venous ectasia). Analysis of high-flow angiopathy changes in such
patients will help in deciding on the best treatment strategy and its timing.
115Ve in of Galen Aneurysmal Dilatation
Fig. 3.7A–D. Ty p ic al aspect of a vein of Galen dilatation in a 2-year-old boy; note the
opening of the left basal vein into the matured and dilated vein of Galen
3Vein of Galen Aneurysmal Malformation116
Fig. 3.8A–D. Ty pical aspect of a vein of Galen dilatation in a 10-year-old boy; note in
addition to the opening of the right basal vein into the matured and dilated vein of
Galen, the cerebral venous congestion of both supra- and infratentorial spaces
3.5 Dural Arteriovenous Shunts
with Aneurysmal Dilatation of the Vein of Galen
Dural AV shunts (DAVSs) with aneurysmal dilatation of the vein of Galen
were described in children by Fournier et al. in 1991; vein of Galen
aneurysmal dilatation (VGAD) was secondary to a vermian AVM with
dilatation of the Galen vein (thrombosis of the straight sinus).
In a 2-year-old boy presenting with intraventricular hemorrhage,
computed tomography (CT) and angiography demonstrated a small
vermian cerebellar AVM with reflux in the Galen vein afferents. A
mild macrocrania had been noted at 3 months but was not further investigated, and the child was shunted (ventricular-peritoneal). Following embolization of the AVM and subsequent surgical removal of
the remainder of the lesion, a 6-month follow-up angiogram demonstrated a dural shunt remote from the surgical field. The AV shunts
were located within the wall of the previously dilated Galen vein.
Feeders corresponded to vasa vasorum of the normal Galen vein,thus
contributing to a nidus type of network extending from the venous
wall into the intraluminal clot partially filling the ectatic lumen.
These lesions are usually seen in adults and probably reflect the longstanding presence of triggering factors and secondary changes before
they become clinically evident (see Vol. 2).
3.6 Vein of Galen Varix
Ve in of Galen varices constitute a group of dilatations of the vein without
the presence of an AV shunt.Two types have been encountered in children.
The first are transient dilatations of the Galen vein in neonates presenting
with cardiac failure of another origin. This dilatation persists for a few days
after birth and then disappears on follow-up ultrasound studies. The dilatation does not lead to any symptoms and the disappearance parallels the
cardiovascular improvement. The second type of vein of Galen varix occurs when hemispheric venous drainage of the brain converges toward the
deep venous system.This condition does not always correspond to a postthrombotic collateral circulation, but sometimes to an obvious anomalous
disposition of the overall venous system (complex DVA).It will not give any
specific symptoms, but the lack of compliance of this type of venous
drainage system over time may create venous insufficiency manifestations.
3.7 Vein of Galen Aneurysmal Malformation
It is possible to distinguish the angioarchitectural differences between an
AVM involving the vein of Galen forerunner, which we call VGAM, and
an AVM with venous drainage into a dilated, but already formed vein
of Galen, which will be called VGAD (Lasjaunias 1987b). The VGAM
involves the choroidal fissure and extends from the interventricular
foramen rostrally to the atrium laterally (Fig. 3.3).
117Ve in of Galen Aneurysmal Malformation
The arterial supply usually involves all the choroidal arteries (Figs. 3.9,
3.10,), including subfornical and anterior choroidal contributions
(Figs. 3.11, 3.12); it may also receive a significant contribution from the
subependymal network originating from the posterior circle of Willis.
These arteries should be differentiated from transmesencephalic arteries
(their involvement, in fact, would exclude the diagnosis of VGAM and
indicate a tectal location of the AVM). The subependymal arteries pierce
the floor of the third ventricle and run subependymal to join the choroid
fissure, where they contribute to the opacification of the lesion. Very
rarely are thalamoperforating arteries recruited, and this occurrence is
grossly overestimated in the literature (Fig. 3.11). Subependymal and
transcerebral contributions appear accessory in the supply to the shunt,
possibly created by the sump effect of the venous drainage.Their contribution can sometimes be used for an endovascular approach (Fig. 3.13),
but they usually disappear following the proper occlusion of the most
prominent shunts (see Fig. 3.14).
The persistent limbic arterial arch (see Vol. 1, Chap. 6), which bridges
the cortical branch of the anterior choroidal artery initially (Fig.3.15)
and the posterior cerebral artery (Fig. 3.16) secondarily with the pericallosal artery, is seen in nearly half of neonatal cases. It should be distinguished from subcallosal and subfornical supply to the choroidal shunts
(Fig. 3.17). Its presence should be anticipated at the time of embolization
into a lateral choroidal artery when it arises far distally along the posterior cerebral main stem. The limbic arterial arch on each side can anastomose and may even fuse on the midline in the supracallosal region
(Figs. 3.18, 3.19). The circle(s) regress (mature) after obliteration of the
VGAM by means of embolization (Fig. 3.17), leaving behind various
anatomical dispositions where the posterior cerebral artery (PCA) supplies the ipsilateral or contralateral para central gyrus (Figs.3.18, 3.19).
Cerebellar arteries do not contribute to the supply of the VGAM, except
3Vein of Galen Aneurysmal Malformation118
Fig. 3.9. Schematic representation of VGAM illustrating
in particular the choroidal
supply as well as the limbic
arterial arch. The subependymal and lamina terminalis
supplies are not represented.
(Courtesy of J. Bhattacharya)
119Ve in of Galen Aneurysmal Malformation
Fig. 3.10A–C. Legend see p. 120
indirectly through their dural branches, which can be enlarged, as they
may participate in the supply to the vasa vasorum at the venodural junction.
Other dural contributions can be seen in true VGAM and may be located at a distance from the choroid fissure shunting zone.They often represent secondary dural AV shunts after sinus thrombosis (usually sigmoid;
Fig. 3.53) or AV dural communications caused by the sump effect from an
otherwise patent sinus [usually the superior sagittal sinus (SSS)].
In three premature babies who presented with severe cardiac failure,
we encountered a rare arterial aspect resembling a moyamoya network
(Fig. 3.20). In all three patients, the damage to the cerebral tissue appeared irreversible and the babies died during the next 48 h.This condition was the only one to resemble an early high-flow angiopathy type of
response of the remaining vasculature to the shunt. Some rare stenoses
are seen along the course of large choroidal feeders to mural types of
VGAM (see below; see Fig. 3.56). Since they are located at the edge of
the tentorium cerebelli, they are likely to express the mechanical effects
of the ectasia by the stiff dural margin on the enlarged feeders. We suspect that a further slight increase in this pressure phenomenon (by
ventricle enlargement) might lead to occlusion of the artery involved.
Subsequent spontaneous thrombosis of the VGAM will occur if the number of compressed feeders to the lesion is limited, as in a mural type of
VGAM.
3Vein of Galen Aneurysmal Malformation120
Fig. 3.10A–E. Female neonates presenting with moderate cardiac overload. A, B Be-
cause of the MRI appearance with enlarged arteries within the capsular region, the diagnosis of vein of Galen was questioned. Angiography was performed (C), showing a
significant intraparenchymal angiectasia joining the choroid fissure on the right side.
Note supply to an arteriovenous fistula at the interventricular foramen. D, E angiogra-
phie and MRI demonstration of the subependymal artery in a retromammilar position
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