Tumors near the brain stem can also block the cerebrospinal fluid pathways and cause hydrocephalus. These pilocytic astrocytoma can be cured by surgery. These tumors are resectable and can also occur in children without NF1. The blood vessels in Moya Moya disease are small and not really adequate to feed their vascular territories. Much of the brain is being fed by collaterals from other vessels.
Some patients develop some strokes because of inadequate blood flow.
There are operations for this. I was not able to find any statistics about whether surgery is more difficult or has a lesser success rate in patients with NF1. There is another procedure where a vascularized substance like the fascia under the scalp or some muscle is laid over the brain to try to encourage new vessels to grow into the brain from the supply in the muscle or fascia. Another finding that occurs with greater frequency in NF1 patients is arachnoid cysts. These are developmental anomalies of the arachnoid, one of the layers covering the brain.