The literature testifies to considerable confusion about the difference between the VOGM and the finding of a dilated (aneurysmal) VOG secondary to an AVM or arteriovenous fistula because of their similar clinical findings. The solution and the angiographic definition of the VOGM was provided by Raybaud, Strother and Hald in 1989 [1] (see below), who were the first to recognise that the dilated midline vessel seen in the VOGM was in fact a persistent median vein of the prosencephalon or vein of Markowski. Before going on, it is worth revisiting the embryology of the cerebral vasculature.

As was described in Tutorial 1, prior to the choroidal vascular stage, the neural tube is nourished by amniotic fluid. After closure, the neural tube is initially supplied by surface vessels of the meninx primitiva, but as the cerebral vesicles develop at the rostral end of the neural tube, an increasing demand for blood supply is met by choroidal vessels (choroidal stage).

The choroidal and quadrigeminal arteries are present by the 5th week and supply the developing choroid plexus. The plexus of the primary prosencephalic vesicle develops along the junction of its division into diencephalon and telencephalon secondary vesicles. The expansion of the telencephalic choroid plexus is accompanied by differentiation of a dorsal vein on the ventral surface of the diencephalon to drain the choroid plexus. This was called the ‘vena medianna prosencephali’ by Hochstetter [2]. He identified that it was transient and only evident between the 8th and 11th week (8–50-mm stage), i.e. at the time the pallium was growing. I will refer to it as the median prosencephalic vein (MPV) (see Fig. 12.1).

Because the choroid plexus develops before vessels have penetrated the neural parenchyma, the MPV is the first vein to drain an intracerebral structure. At this stage, the choroid plexus is supplied largely by choroidal branches of the anterior cerebral artery. By the 12th week, the MPV regresses and its distal remnant joins with the paired internal cerebral veins to form the vein of Galen. It is assumed that the efferent veins of the MPV (and rostral VOG) persist with it, as one possible configuration (choroidal type) of VOGM.

The formation of the dural sinuses is complex and results from the fusion of multiple separate venous plexi. A transient falcine sinus connecting the VOG to the superior sagittal sinus has frequently been observed in the foetus and is often present with the VOGM. It is occasionally present in neonates and infants as a normal variant, but the embryology is unclear.

Early descriptions of the VOGM failed to appreciate that the cause lay in a regression failure of this embryology. Enlargement of the ‘VOG’ was first described by Steinheil in 1895 [3] as a varix aneurysm, and the condition became known as the aneurysm of the vein of Galen.

Litvak et al. in 1960 [4] were the first to recognise the difference between the lesion associated with the MPV and other causes. They described primary and secondary aneurysms of the VOG, distinguishing midline arteriovenous fistulas from AVMs as causes for the dilated VOG. Gold et al. in 1964 [5] provided a clear description of the modes of presentation of what they called the vein of Galen malformation. They recognised three clinical types: (a) neonates presenting with congestive heart failure, (b) infants presenting with hydrocephalus and seizures and (c) older children and adults presenting with headaches and spontaneous intracranial haemorrhage. Amacher and Shilitto [6] added a fourth group: infants and young children presenting with increasing head size and mild congestive heart failure.

In 1988, Yasargil [7] described a classification of the angiographic findings in patients with arteriovenous shunts to the VOG. This distinguished four types:

In 1989, Raybaud et al. [1] published their paper advancing a coherent argument that aneurysmal dilation of the VOG was due to persistence of the rostral component of the MPV based on a detailed analysis of 23 cases with only 12 complete sets of angiograms. They argued that an embryonic insult between 6 and 11 weeks caused the condition in neonates and infants. They showed that the fistula arose from subarachnoid choroidal and quadrigeminal (collicular) arteries and that normal deep venous drainage of the brain was diverted away from the dilated VOG (because no normal connection was ever established between the developing internal cerebral veins and the persistent MPV). They identified several abnormalities of the venous drainage from the MPV: principally absence of the straight sinus in 50% of their cases, stenosis and absence of the sigmoid sinus, persistence of the falcine sinus and an anomaly they described as a falcine loop. However, they proposed that the term aneurysmal VOG be retained (Fig. 12.2).

The classification of aneurysmal VOGs was simplified by Berenstein and Lasjaunias [8] who proposed separating malformations draining to the persistent MPV into mural and choroidal types and that the term vein of Galen malformation (VOGM) be used only for arteriovenous shunts to the MPV.

The two VOGM types were defined as:

The features common to both types are drainage to the MPV, no connection with the normal deep venous drainage of the brain and an arterial supply from the posterior choroidal arteries (Raybaud et al. found it difficult to distinguish posterior medial from posterior lateral choroidal arteries, Fig. 12.2).

Relative distinguishing features are the earlier presentation in the neonatal period (i.e. within 28 days of birth) of the choroidal VOGM. It is always associated with heart failure, a falcine sinus (together with absence of the straight sinus) and usually with patent sigmoid sinuses. Babies presenting with congestive heart failure have abnormalities of CSF absorption and failure to thrive.

The mural VOGM tends to present later in infancy (i.e. 6 months to 3 years) with symptoms and signs of increasing head size, cardiac failure (of lesser severity than neonates with choroidal VOGM), failure to thrive and hydrocephalus. Falcine sinuses may or may not be present and obstructions of the sigmoid sinuses are more commonly seen, in which case drainage of the VOGM is redirected anteriorly via the basal veins, to the cavernous sinuses, orbital veins or transosseous scalp veins. The cavernous sinuses are normally rudimentary at birth and develop over the first 18 months of life. Without them, drainage from the VOGM is redirected to these alternative routes.

The VOGM arterial feeders were summarised by Brunelle [10] as 100% posterior choroidal arteries (medial and lateral), 69% anterior cerebral artery (trigonal branch of the pericallosal artery) and 30% ‘transmesencephalic’ (midline arteries arising directly from the basilar artery (BA). The relative contributions of common arterial feeders to the two types distinguished by Berenstein and Lasjaunias [8] are summarised in Table 12.1. Less commonly, either type receives contributions from anterior choroidal or lenticulostriate arteries and rarely from the middle cerebral artery.

All other fistulas associated with aneurysmal dilatation of the VOG do not involve a persistent MPV and therefore develop subsequent to the embryonic period and after the development of a normal pattern of deep venous drainage to (and from) the VOG. In this tutorial, they will be considered together with cerebral arteriovenous (non-Galenic) fistulas that arise elsewhere in the brain and also usually present in children and young adults.

The presenting symptoms in a series of 232 patients (predominantly children) were reviewed by Johnston et al. [11] and are summarised in Table 12.2. Only 9% were adults and approximately 50% presented with congestive heart failure. There is a modest male predominance in the incidence of the VOGM (1.7:1).

Symptoms due to the high-flow arteriovenous shunts are: