Vein of Galen malformation

• AVF draining to median prosencephalon vein of Markowski (a precursor of vein of Galen)

• congenital malformation that develops during weeks 6-11 of fetal development as persistent embryonic prosencephalic vein of markowski.

• Prosencephalic veins drain into the vein of Galen.

• Rare anomalies of intracranial circulation

• Constitute 1% of all intracranial vascular malformations

• Represent 30% of vascular malformations presenting in the paediatric age group

• Incidence: 1/3mil population per year

Normal development of dorsal cerebral vasculature

• The Choroid Plexus is
• supplied by the
• Anterior cerebral (ACA)
• Choroidal arteries (Chor A)
• Drains into the
• median prosencephalic vein (Med Prosen V)

• Development of the internal cerebral veins (Int Cereb V) results in the regression of the median prosencephalic vein

• Disease



• This abnormal development occurs between 6-11 weeks of intrauterine life
• Location of the AV fistula is within the cistern of velum interpositum and quadrigeminal cistern
• Arteriovenous fistulous communications prevent regression of the median prosencephalic vein
• Ectatic venous structure characteristically seen in the lesion represented the median prosencephalic vein and not the vein of Galen itself
• Arise as a result of direct arteriovenous communications
• between
• Arterial network
• Principal feeders of malformation are those that normally supply the tela choroidea and the quadrigeminal plate including:
• The anterior or prosencephalic group
• Anterior cerebral (ACA)
• Anterior choroidal (Chor A)
• Middle cerebral (MCA)
• Posterolateral choroidal arteries
• The posterior or mesencephalic group
• Posteromedial choroidal
• Posterior thalamoperforating
• Quadrigeminal
• Superior cerebellar arteries (Collic A)
• median prosencephalic vein
• lacks a fibrous wall therefore is unsupported --> can balloon out to a large size
• Ectatic venous structure characteristically seen in the lesion represented the median prosencephalic vein and not the vein of Galen itself
• lies free in the subarachnoid space within the cistern of velum interpositum
• Venous drainage
• into the
• Falcine sinus (Falc S)
• high flow across the arteriovenous fistula may result in retention of foetal patterns of venous drainage
• Persistence of falcine sinus, which is supposed to be a transient embryonic structure that connects the straight sinus to the superior sagittal sinus
• hypoplasia of the straight sinus (Str S)
• Retention of foetal patterns of venous drainage (falcine sinus) could prevent development of other sinuses such as the straight sinus.

 
• Retention of the embryonic pattern of vasculature can explain the presence of the several vascular anomalies associated with the VOG malformation.
• Aneurysmally dilated midline deep venous structure, fed by abnormal arteriovenous communications

flowchart LR
    linkStyle default stroke:White,stroke-width:4px
    Neonate --> Infant --> Child1 --> Child2

    subgraph Neonate [Neonate]
    direction TB
    style Neonate fill:#a96648
    A[Congestive Heart Failure] --> A1[Multiorgan Failure, encephalomalacia]
    end 
        
    subgraph Infant [Infant]
    direction TB
    style Infant fill:#854e33
    B[Macrocrania, Hydrocephalus]
    B --> B1[Dural Sinus Thrombosis]
    B1 --> B2[Dural venous congestion and supratentorial pial reflux, Bone hyperthrophy] --> B7[Facial venous collarteral, Epistaxis]
    B2 --> B8[Convulsion, Neurological deficits, ICH]
    B1 --> B3[Infratentorial pial reflux and congestion]
    B3 --> B4[Tonsilar Herniation]--> B5[Cerebellar and Brainstem Compression]
    B4 --> B6[Syringohydromyelia]
    end
    
    subgraph Child1 [Child <5 years]
    direction TB
    style Child1 fill:#6d3918
	  C[Neurocognitive Delay]
    end 
    
    subgraph Child2 [Child >5 years]
    direction TB
    style Child2 fill:#58300a
    D[ependymal atrophy] --> D1[Pseudo-ventriculomegally, calcification] --> D2[Epilepsy, neurological deficits]
    end
    

• Cardiac manifestation: Neonates with VOG malformations the cardiac failure is multifactorial in origin and usually refractory to medical management
• High flow of blood through the fistula can lead to cardiac output
• Cardiac high output failure
• 80% of the left ventricular output may be supplied to the brain in severe cases.
• High flow across the pulmonary vasculature --> pulmonary hypertension
• High venous return to the right atrium promotes right-to-left shunting through
• Patent foramen ovale
• Ductus arteriosus
• Remains patent due to the rise of pulmonary arterial pressure above the systemic pressure.
• These right-to-left shunts are responsible for the cyanosis that may occur in these patients
• Cardiac ischaemia due to reduction in endocardial blood flow because:
• Arteriovenous shunts --> reduce the diastolic pressure within the aorta --> reduced coronary artery flow.
• Increased cardiac output results in high ventricular intracavity pressure

• Neurological
• Cerebral venous hypertension
• is the factor that is responsible for most neurological manifestations of VOG malformations.
• Due to
• high flow fistula
• Venous anomalies in the form of
• poorly developed venous drainage
• secondary venous stenosis and occlusion
• The high venous pressure transmitted to the medullary veins prevents resorption of fluid and thus results in
• Hydrocephalus
• Due to
• Impaired resorption of CSF
• In infants, the arachnoid granulations have not fully matured, so most of the ventricular CSF is reabsorbed across the ventricular ependyma, into the brain parenchyma, for subsequent drainage by the medullary veins
• Can also less commonly be obstructive from aqueduct compression
• Cerebral oedema
• Hypoxia
• from venous hypertension results in progressive cerebral parenchymal damage resulting in cognitive impairment, which can range from delayed milestones to mental retardation

• Others
• Prominent facial veins (commonly seen in these infants) + epistaxis
• fistula may be drained by rerouting its flow into the cavernous sinus and further into the facial veins or basilar or pterygoid plexus.

• Untreated VOG malformations have a poor prognosis
• Neonates
• 100% mortality
• 1-12 months old:
• 60% mortality
• 7% major morbidity
• 21% normal

• Gold et al (1964): clinical classification system correlating age at presentation with the clinical presentation and pathophysiology and described three groups
• Neonates
• Multiple fistulas​
• 25% of cardiac output passing through fistula causing high output cardiac failure
• Depending on various factors, the cardiac manifestations can range from asymptomatic cardiomegaly to severe cardiac failure that is refractory to medical management
• Cyanosis can be seen in these patients and mistaken for congenital cyanotic heart disease​
• Cranial bruit and marked carotid pulses​
• Bicetre neonatal evaluation score Lasjaunias 1997

Points	Cardiac Function	Cerebral Function	Respiratory Function	Hepatic Function	Renal Function
5	normal	normal	normal	ㅤ	ㅤ
4	overload, no medical treatment	subclinical, isolated EEG abnormalities	tachypnea, finishes bottle	ㅤ	ㅤ
3	failure; stable with medical treatment	nonconvulsive intermittent neurologic signs	tachypnea, does not finish bottle	no hepatomegaly, normal hepatic function	normal
2	failure; not stable with medical treatment	isolated convulsion	assisted ventilation, normal saturation Fi02 < 25%	hepatomegaly, normal hepatic function	transient anuria
1	ventilation necessary	seizures	assisted ventilation, normal saturation Fi02 > 25%	moderate or transient hepatic insufficiency	unstable diuresis with treatment
0	resistant to medical therapy	permanent neurological signs	assisted ventilation, desaturations	abnormal coagulation, elevated enzymes	anuria

Maximal score = 5 (cardiac) + 5 (cerebral) + 5 (respiratory) + 3 (hepatic) + 3 (renal) = 21
• Children and infants
• Single fistula with smaller shunt
• Cardiac manifestations are absent or very mild​
• Macrocephaly or with hydrocephalus​
• Longstanding cerebral venous hypertension – delayed milestones​
• High proportion – failure to thrive​
• Due to Cardiac decompensation, hypothalamic and hypophyseal dysfunction secondary to venous congestion
• Older children
• Low flow fistulae
• Usually present with headache and seizures
• Small number also present with developmental delay, focal neurological deficits, proptosis and epistaxis
• SAH and ICH can also occur

• US
• Antenatal US
• venous sac appears as a mass located posterior to third ventricle.
• Pulsatile flow within helps to differentiate.
• Visualize hydrocephalus, cardiac dysfunction
• Postnatal US
• Assess haemodynamic changes.
• Useful serial follow up in pts treated with endovascular therapy.

• CT
• Well defined multilobulated intensely enhancing lesion.
• Dilated vents.
• Periventricular lucency, diffuse atrophy.
• Diffuse ischaemic change

• MRI
• Useful to demonstrate location of fistula, presence of nidus, arterial components, venous sac and status of venous drainage
• Assess for thrombus within VOG malformation

• Angiography
• Gold standard
• Better at demonstrating small feeders as well as dynamic aspects
• Venous drainage of normal brain



~Large arrow: persistent falcine vein
~Small arrow: hypoplastic straight sinus

• Hydrocephalus - VPS
• Indication
• If obstructive HCP - Requiring shunt. Risks with precipitating haemorrhage

• VOG malformations
• Limited efficacy of operative treatments for those in poor medical condition
• Untreated
• Very poor prognosis
• High proportion who present in neonatal period rapidly deteriorate and succumb to congestive cardiac failure
• Rapid/aggressive tx of cardiac failure is essential.
• Aggressive medical mx can usually postpone an intervention until child aged 5-6months – intervention easier and safer
• Emergency embolization of the malformation may be necessary to reduce the shunt in neonates with CCF that is refractory to medical therapy
• Surgery Vs Endovascular
• Surgical
• Issues with surgery
• Despite technological advances – complete elimination of lesion rarely achieved
• Major surgery
• Deep-seated
• High-flow shunt in infant with multiorgan failure compounded by poor myelination of brain parenchyma
• Parenchyma tears easily on retraction
• Shunting can worsen cerebral venous hypertension
• Aim to avoid before elimination of AV shunt
• Endovascular
• Aim
• to reduce the volume load initially
• to arrest the cardiac failure
• attempt to finally obliterate the shunt completely
• Indication
• Refractory cardiac failure
• Acute or symptomatic hydrocephalus
• Rapid neurological deterioration
• When parenchymal calcifications appear on follow-up scanning of brain.
• Not indicated in because
• poor clinical outcome in spite of successful closure of the shunt by embolization.
• Encephalomalacia
• Severe brain damage
• Severe parenchymal loss
• Technique
• If able to access femoral vein or artery
• Transarterial embolization
• Used when the feeding arterial branches from the choroidal and perforator arteries are big enough to permit microcatheters passage.
• Transvenous embolization
• Used when
• the perforating arteries are too small to permit microcatheters passage
• the shunt is very large with extremely high flow
• Venous approach is preferred to avoid migration of the embolic material when delivered by the transarterial route.
• Occasionally it is necessary to use a combination of both techniques.
• If unable to access femoral vein or artery
• Neonates: Occipital bone over the torcular is penetrated with a large bore needle for catheterization of the varix
• Children: Occipital burr-hole is used
• Staging of the embolization
• Required in most infants and children
• Ranging from a few weeks to a few months based on the angioarchitecture and clinical status.
• The follow-up endovascular approach is based on the residual shunt and the architecture of the malformation.
• If the intervals between embolization is too long can lead to Occlusive venopathy
• a well-known delayed event causing progressive neurological deterioration.
• The acquired venopathy may be fatal.
• Mech:
• too long intervals between the embolization procedures --> high venous pressures in the dural sinuses and cortical veins --> back pressure in the medullary veins and cortical veins --> progressive parenchymal calcifications +refractory seizures.

• Potentially fatal

• Normal perfusion pressure breakthrough

• Intracerebral haemorrhage due to venous hypertension

• Can be reduced/avoided by staging the embolization procedures

• Perforation of venous sac

• Ischaemic deficits

• Pulmonary embolisation with embolic agents is common considering the high flow across the intracranial shunt