Keywords
twin anomaly - twin pregnancy - vein of Galen aneurysmal malformation
Case Report
A 32-year-old woman with a monochorionic-diamniotic twin gestation was referred at
23 weeks for suspected fetal cardiac anomalies for twin A. Upon transfer, the fetal
echocardiogram in twin A showed a reversal of flow in the ductus arteriosus and a
dilated superior vena cava and innominate vein. On follow-up fetal echocardiogram
at 28 weeks, twin A was found to have borderline cardiomegaly, reversal of flow at
the aortic isthmus, and findings concerning increased vascularity in the fetal brain.
She was urgently referred to the Maternal-Fetal Medicine ultrasound unit where a cystic
midline structure with turbulent blood flow was identified measuring 2.4 × 2.0 cm,
as well as dilation of the straight sinus (8.7 mm at thinnest point and 12 mm thickest
point), consistent with vein of Galen aneurysmal malformation (VGAM) ([Fig. 1]). A 29 weeks ultrasound showed new mild polyhydramnios for both twins (deepest vertical
pocket 9.1 cm/9.3 cm) and antenatal corticosteroids were administered. She underwent
twice weekly biophysical profiles with reassuring results and the polyhydramnios remained
mild for both twins. However, subsequent fetal echocardiograms at 30 and 32 weeks
showed worsening cardiomegaly with dilation of the right atrium and ventricle in twin
A. Fetal magnetic resonance imaging (MRI) at 30 weeks confirmed VGAM and showed otherwise
normal cerebral parenchyma ([Fig. 2]). While limited due to the large VGAM, ultrasound at 32 weeks suggested possible
interval disruption in the brain parenchyma. A multidisciplinary meeting was held
and given possible signs of progression of the lesion by ultrasound, to optimize outcomes
for the unaffected twin, a plan was made for a 34-week delivery to balance the risk
of worsening status and intrauterine demise of the affected twin with the risks of
prematurity for the unaffected twin.
Fig. 1 Color Doppler transabdominal ultrasonography at 28 weeks showing an axial view of
twin A's head with (a) vein of Galen aneurysmal malformation with comet tail sign and (b) dilated straight sinus.
Fig. 2 Magnetic resonance imaging at 30 weeks showing vein of Galen aneurysmal malformation
with normal surrounding brain parenchyma.
At 326/7 weeks, a nonstress test for twin A was nonreactive with recurrent variable decelerations,
and emergent repeat cesarean delivery was performed. Twin A was intubated shortly
after birth for respiratory failure, started on dopamine for hypotension, and found
to be in high output cardiac failure. Postnatal brain MRI showed cerebral atrophy
and chronic global ischemia suggesting poor neurological prognosis; therefore, postnatal
embolization was not offered. On day of life 5, the parents decided on a do-not-resuscitate
order, and twin A died on day of life 9. Twin B had a routine neonatal intensive care
unit stay for prematurity and was discharged in stable condition. Placental dye studies
were performed showing dilated and poorly arborized vessels on twin A's portion of
the placenta ([Fig. 3]).
Fig. 3 Placental dye studies with twin A right (vein green, artery orange) and twin B left
(vein blue, artery red).
Discussion
VGAM is a rare congenital cerebral arteriovenous malformation (AVM) between the choroidal
vessels and the median prosencephalic vein of Markowski, which prevents its involution
into the vein of Galen.[1] If diagnosed prenatally, the diagnosis is typically made in the third trimester
with color Doppler ultrasonography and is commonly associated with hydrocephalus,
ischemic brain injury, and cardiomegaly with high output cardiac failure as a result
of shunting of blood to the AVM.[2]
[3] While endovascular embolization is a potential cure for VGAM, it is ideally performed
at 4 to 6 months of age if the patient remains stable, but many neonates are not candidates
for this intervention due to the complexity of the lesion, the extent of brain injury
at birth, or the severity of heart failure. Therefore, the mortality rate is up to
32% in singletons.[4]
There are few data on the morbidity and mortality of VGAM in twin pregnancies. Of
the four published cases of VGAM in twin pregnancies to date, only one affected twin
survived.[5]
[6]
[7]
[8] This twin was part of a monochorionic-diamniotic pair delivered at 25 weeks for
nonreassuring fetal status with postnatal diagnosis of VGAM.[7] The two cases with prenatal diagnosis of VGAM were dichorionic twin pregnancies (one with preterm birth at 35
weeks due to preterm labor and the other with planned 37 weeks delivery); both of
the affected fetuses died in the neonatal period in the setting of heart failure and
inability to successfully embolize the AVM.[5]
[8]
Determining the optimal timing of delivery for pregnancies diagnosed with VGAM is
challenging and no current guidelines exist; therefore, management must include a
multidisciplinary approach. The risk of in utero progression of the AVM (and its associated
impact on the developing brain and heart) must be weighed against risks of prematurity
to increase survival and optimize the neonate for endovascular intervention. Ultrasound
features associated with poor prognosis include tricuspid regurgitation and AVM volume > 20,000 mm3, which can help guide prenatal counseling and management.[4]
The challenge of delivery timing is further complicated in twin pregnancies, especially
monochorionic twins, given the demise of the affected twin imparts a risk of neurological
injury and the demise of the healthy cotwin.[9] In our case, to optimize outcomes for the healthy twin per the patient's wishes,
prevention of an intrauterine fetal demise of the affected twin was critical due to
the shared placental circulation. This ultimately led to a preterm delivery at 32
weeks. However, the heart failure had already progressed and neurological injury was
already severe (despite normal brain parenchyma on prenatal MRI).
The timing of delivery of fetuses with VGAM is often dictated by other complications,
especially among twin gestations. In the other mentioned published cases of VGAM in
twin pregnancies, preterm birth occurred in three out of four cases; two for fetal
distress (one in the setting of twin-to-twin transfusion syndrome) and one as a result
of preterm labor.[5]
[6]
[7] The one affected twin in the literature who survived was born at 25 weeks (for fetal
distress) but only had mild heart failure therefore remained stable through two embolization
procedures at 6 and 8 months of life.[7]
Given the rare clinical scenario of VGAM in twins, it remains unclear how to counsel
and manage patients after prenatal diagnosis is made, and guidelines around delivery
timing are limited. It remains to be determined if early delivery is associated with
less severe heart failure or less extensive neurological injury, and if so, if these
benefits outweigh the impact of prematurity on prognosis. This case contributes to
our greater understanding of this rare diagnosis for the management of both singletons
and twins.
