Vein Of Galen Aneurysmal Malformations Health And Social Care Essay

Vein of Galen aneurysmal malformations (VGAMs) are rare congenital vascular malformations composed of a dilated vein of Galen with abnormal communications from adjacent arteries. It was suggested that the abnormality was due to the persistence of an embryonic channel, the median prosencephalic vein of Markowski, which participates in the formation of the vein of Galen (1). VGAMs classically present in the neonatal period as high out put heart failure. The dilated vein can compress the cerebral aqueduct leading to hydrocephalus (2, 3). Focal neurologic deficits and seizures are other findings. Older patients can present with headache, visual defects, syncope, subarachnoid hemorrhage and mental retardation. Improvement in fetal and postnatal imaging techniques allows an earlier diagnosis of VGAMs and appropriate management of these patients. Several studies have emphasized the role of fetal MRI and echocardiography in early detection and characterization of the VGAMs, document presence of other brain abnormalities, detect cardiac insufficiency and pulmonary hypertension (4). In this report, we present autopsy findings of three neonates with VGAMs, correlation with clinical imaging studies (fetal ultrasound, MRI and echocardiography), clinical features and prognosis.

Case Reports

Case 1

The patient was born to a 39-year-old primigravida at 38-5/7 weeks of gestational age. A prenatal ultrasound at 29 weeks of gestational age revealed a singleton fetus with an expected estimated body weight of 1649 gm, polyhydraminos and a large vein of Galen aneurysmal malformation (figure 1A). Fetal echocardiogram showed sinus tachycardia of 190 beats/minute, moderate cardiomegaly (cardiothoracic index, 72%), right atrial and ventricular dilation and dilation of the superior vena cava (figure 1B). In addition, there was moderate tricuspid insufficiency, and right-to left shunt across a patent foramen ovale (PFO) and patent ductus arteriosus (PDA). Fetal MRI confirmed a large VGAM with associated cerebral hypoplasia, brain atrophy, thinning of the corpus callosum and dilatation of the lateral ventricles (figure 2A and 2B). The birth weight was 3590 grams and the APGAR scores were 1 and 4 at 1 and 5 minutes. The patient required intubation due to a poor respiratory effort and subsequently developed metabolic acidosis and expired on the second day of life.

Autopsy examination revealed that there is no aneurysm in the circle of Willis at the base of brain. However, there is prominent dilatation of surface small vessels in the regions around middle and anterior cerebral arteries (figure 3A). There is a significantly dilated vein of Galen and straight sinus with bilateral anastomosis to the posterior cerebral arteries (figure 3B). The other significant findings were microcephaly (158 grams), hydrocephalus, partial agenesis of anterior corpus callosum and polymicrogyri of the frontal and temporal lobes. There was marked cardiomegaly (57 grams) with dilated superior and inferior vena cava (figure 4). There was a large PDA. The histological examination revealed subendocardial fibrosis in the right ventricle. The lungs revealed congestion, focal intraparenchymal hemorrhage with intraalveolar acellular squames suggesting fetal stress.

Case 2

The case 2 was a female infant, born at 34 4/7 weeks of gestational age to a G2P1 22 year-old mother. A prenatal ultrasound revealed VGAM. There was also intrauterine growth retardation, oligohydramnios, and reversed end diastolic flow. The mother was admitted with complaint of premature labor. The birth weight was 1685 gram and the APGAR scores were 7 and 7 at 1 and 5 minutes. Echocardiogram revealed dilated right atrium, right ventricle with markedly diminished cardiac systolic contractility consistent with high-output cardiac failure. The patient required mechanical ventilation and eventually developed metabolic acidosis, shock and expired within few hours of birth.

Dissection of the vascular structures of the brain showed multiple vascular channels connecting the right posterior cerebral artery to the dilated vein of Galen. In addition, there was diffuse dilatation of venous sinuses in the posterior fossa, hydrocephalus, and germinal matrix hemorrhage. The heart weighed 32 grams (expected 12.4gm +/- ) with severe dilatation of the right ventricle.

Case 3

Patient 3 was a 5-day-old African-American male born to a 21 year-old mother, G3P2 at 36 1/7 weeks of gestation via C-section. Prenatal ultrasound at 35 weeks showed a large intracranial "cyst". The birth weight was 3000 grams and the APGAR scores were 4 and 7 at 1 and 5 minutes. Echocardiogram revealed a PFO and PDA with bidirectional shunting. The right atrium and ventricle were dilated consistent with high-output cardiac failure. MRI and magnetic resonance venography (MRV) demonstrated a 2.4 cm "arteriovenous malformation" impinging on the right cerebellar hemisphere and narrowing of the 4th ventricle with secondary hydrocephalus. The fistula was supplied by numerous branches of both vertebral arteries and many choroidal branches of both posterior cerebral arteries. The right transverse sinus was also enlarged. An embolization was performed to obliterate the main fistula. However, many residual fistulae were not treated due to severe hemodynamic instability. After surgery, the heart failure and circulatory insufficiency worsened and patient developed multi-organ system failure. The patient expired shortly afterwards.

Autopsy of Patient 3 demonstrated a partially embolized VGAM involving the right cerebellar hemisphere and ventral brainstem. The posterior circulation, including the posterior cerebral, superior cerebellar, anterior-inferior cerebellar, and posterior-inferior cerebellar arteries were markedly dilated. There was a direct communication of right posterior cerebral artery to the malformation. The anterior circulation at the base of the brain was unremarkable. In addition, the internal cerebral vein was dilated and connected to the right transverse sinus. There was extensive subarachnoid hemorrhage involving the left temporal, occipital and parietal lobes. There were many dilated abnormal small vessels in right cerebellum and ventral midbrain. Organized thrombi were seen in right cerebellum. In addition, there were hydrocephalus, global hypoxic ischemic brain injury, pontosubicular necrosis, and periventricular leukomalacia. The heart weight (45.8 grams) was significantly increased and showed dilatation of PDA, right ventricle and atrium. There were also medial hypertrophy of muscular pulmonary arteries and muscularization of lobular arterioles consistent with pulmonary hypertension.

Discussion

VGAMs are intracranial vascular malformations representing less than 1% of all cerebral vascular malformations but represent up to 30% of all pediatric cerebral vascular malformations (1). Although it has been found that this malformation develops between 6th and 11th weeks of gestation after development of the circle of Willis (5), in our reported cases, the VGAMs were detected by the ultrasound and confirmed by MRI between 29 to 35 weeks of gestational age. In all three VGAMs, communicating vessels were found either from unilateral or bilateral posterior cerebral arteries. It is thought that VGAMs result from development of an arteriovenous connection between the primitive choroidal vessels and the median prosencephalic vein of Markowski. This vein should disappear at 11th weeks of gestation. Its persistence constitutes the Vein of Galen malformation.

The autopsy examination of all three cases revealed cardiomegaly with dilation of right atrium and ventricle consistent with the echocardiographic findings of high output cardiac failure. Newborns with VGAMs typically present with severe cardio-respiratory symptoms at, or shortly after birth. These infants may show symptoms of cardiac failure including hydrops in utero. The volume overload due to high-flow shunts can rapidly induce cardiovascular and respiratory distress in these infants (1). The majority of cases (94%) diagnosed in the neonatal period present with high-output cardiac failure (6, 7). The other complicating factor is the development of severe pulmonary hypertension, which carries a poor prognosis (1, 3, 4, and 7). Infants and children tend to present with hydrocephalus, developmental delay, megaencephaly, seizures, headache or focal neurological deficits (8). Cardiac failure, when present in infants and children, is milder and more amenable to treatment and pulmonary hypertension is not a prominent symptom (9). Older children and adults may present with headache that may or may not be associated with subarachnoid hemorrhage. In a study by Gold at al subarachnoid hemorrhage occurred in 10 out of 13 patients in this age group (10).

The data from our cases suggest that when a VGAM is large enough to be detected prenatally, the likelihood of perinatal cardiac failure increases dramatically. This finding corresponds with the previous studies (1, 6, 8, 9). The first two patients had signs of volume overload and cardiac decompensation at 28 to 29 weeks of gestation, evidenced by cardiomegaly, substantial tricuspid regurgitation, and sinus tachycardia.

A prenatal ultrasound of the third patient reported the malformation as large intracranial "cyst". Although a cardiac failure was not detected initially, the patient was born with a severe high-output cardiac failure. Currently, once VGAM's were detected in utero by widely used ultrasound study, they are often confirmed by fetal MRI (11, 12 & 13). Our third case suggests that the cardiac failure may not present at the time of VGAM was detected but may occur later. The neonatal prognosis is poor if fetal cardiac insufficiency occurs in utero. A subsequent periodic ecocardiography should be performed to monitor the status of the cardiac function. Echocardiography has a primary role in assessing ventricular function, pulmonary artery pressures, and degree of shunt across PDA, and associated anomalies. In addition, echocardiography may reveal reversal of aortic flow during diastole, indicating a steal phenomenon that decreases peripheral perfusion (7, 14, 15).

It has been noted that children with VGAMs presenting during neonatal period have a generally much worse prognosis than those presenting later in the childhood (16). The optimal care for this group of patients has not been defined. However, this study confirms, as previously reported (10&17), that the infants with prenatal brain abnormalities, such as hydrocephaly, polymicrogyri, periventricular leuckomalacia, acompanied vascular malformation with hemorrhage remain associated with unfavorable outcome. In addition, the hemodynamic parameters mimicking persistent fetal circulation are poor prognostic markers of the disease as seen in two of our patients (18).

Our autopsy finding demonstrated communicating vessels from posterior cerebral artery to the VGAM. This finding supports that the malformation is due to the shunting from an artery to the vein of Galen during early embryonic development. The outcome of the neonates having VGAM with high output cardiac failure and other intracranial abnormalities is poor. Fetal MRI will confirm the diagnosis of VGAM and also give additional information about other associated brain abnormalities. Echocardiography and close follow-up during prenatal and postnatal period will document cardiac failure and assist in appropriate management of these patients.