What would need to be done to fully characterised its arterial supply?
The vertebrobasilar system would have to be injected as there is likely to be supplied also from the posterior cerebral arteries (this is especially likely as the vertebral arteries seem large on the CT scan).
How does the AVM drain?
Via very enlarged cortical veins to the superior and sigmoid dural sinuses.
Right common carotid artery angiogram demonstrates a ~1.5cm nidus supplied predominantly by the right middle cerebral artery. The AVM has superficial drainage via markedly enlarged cortical veins, which drain in the dural sinuses. No deep drainage was identified.