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

• Choroid Plexus vasculature:
• 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
    

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

• 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