Blood is diverted away from other organs into the VGM; this results in failure of these organs, such as the heart. It is also difficult for the veins to do their job of soaking up and circulating water from the brain and so fluid may collect within the brain (see entry hydrocephalus). There is also a risk of bleeding from the abnormal vessels, although this is relatively low.
The symptoms of VGM will vary between individuals, although some patterns are recognised:
- neonatal (after birth) presentation: some babies present with heart failure in the early days of life (see above)
- infants may have difficulties in reaching developmental milestones, or may have a large head size (due to increased water in the brain)
- older children may have seizures, developmental difficulties or a large head size.