Antenatal vein of Galen malformation with high output cardiac failure

A 19-year-old primigravida with a natural pregnancy was referred for an antenatal growth scan at 34 weeks of gestation. Her previous scans at 6 and 13 weeks were normal, but she missed her 18–22-week scan. The patient has no significant surgical or medical history.

On the ultrasonography scan (USG), a centrally located, oval-shaped anechoic structure (Figure 1) with prominent flow on Doppler study (Figure 2) was identified, measuring  5,000 mm³ (5 mL). High velocity and low resistance with increased flow volume were noted. This structure was draining into the dilated sagittal sinus. A prominent, dilated linear structure with an arterial Doppler pattern was observed entering laterally (Figure 3). The third ventricle was mildly dilated anteriorly, but there was no thinning of the cerebral cortex. The jugular veins and superior vena cava were also dilated (Figure 4). The umbilical and bilateral uterine Doppler studies were normal.

The cardiac size was enlarged, with the right-sided chambers being more affected, and the cardiothoracic ratio measured 0.6 (Figure 5). There was no tricuspid regurgitation (TR), and no cardiac anomalies were seen. Mild pericardial and pleural effusion were noted (Figure 6). Minimal ascites was present (Figure 7).

The amniotic fluid index was 14 cm, and no other foetal anomalies were observed.

Foetal central nervous system (CNS) malformations are structural abnormalities in the brain that develop during pregnancy, affecting approximately 0.3–1% of all live births [1]. These malformations can be detected through prenatal imaging, and early detection and diagnosis are crucial for managing and planning appropriate care. Treatment options and outcomes vary widely depending on the type and severity of the malformation. One such rare abnormality is the foetal vein of Galen malformation (VGM), which accounts for about 1% of foetal CNS malformations [2].

Embryologically, the development of the deep cerebral veins, including the middle cerebral veins and the vein of Galen, originates from a precursor known as the median prosencephalic vein (MPV). By the 11^th week of gestation, the MPV typically regresses to form the deep cerebral veins [3]. However, a vein of Galen malformation occurs due to a fistulous connection between the cerebral arteries and the MPV. As a result, the MPV fails to regress and becomes aneurysmally dilated [4–6].

Our case illustrates the typical presentation of a vein of Galen malformation (VGM), diagnosed later in pregnancy. Although this rare malformation often presents with a straightforward diagnosis, the associated features are of critical importance, particularly the presence of an extracardiac left-to-right shunt leading to high-output cardiac failure. One of the largest observational studies on VGM, conducted by Paladini et al., identified predictors of poor outcomes to be dilation of the straight sinus, VGM volume ≥ 20,000 mm³ (20 mL), and tricuspid regurgitation [7].

In our case, there was no tricuspid regurgitation, and the volume of the VGM was only 5,000 mm³. Despite the absence of these poor prognostic indicators, our case exhibited initial signs of heart failure. We could assume that the presence of signs of heart failure points towards a poor prognosis. The prognosis is also believed to depend on the severity of heart failure, which is directly linked to the size of the shunt. Additionally, the presence of cerebral ischemia, caused by increasing venous pressure—a phenomenon known as cerebral steal—also plays a significant role [8]. Therefore, the precise size or limit of the shunt that leads to a poor prognosis has yet to be determined.

The predictors for the outcome are important in this malformation to guide the clinician towards appropriate immediate postnatal treatment and proper patient counselling. Prenatal MRI is essential for assessing foetal parenchymal lesions due to its detailed imaging capabilities. It helps differentiate the extent, and identify associated abnormalities. This detailed information aids in prognosis, guides the delivery planning, and allows for effective monitoring and early interventions. Untreated VGM is universally fatal [9]. Before the advent of endovascular interventions, the outcomes of open surgical procedures were poor [10]. Currently, the preferred treatment involves transarterial embolisation after birth. The effectiveness of this procedure largely depends on the size of the malformations [11–13].