Present with hydrocephalus or else cardiac failure in neonatal period. Clue is that heart is structurally normal!

Life time risk of haemorrhage is high, presenting with headache or seizure.  Annual rate about 6%.  Focal neuro signs rare prior to haemorrhage!  Risk slightly higher in deep locations eg basal ganglia.

Once haemorrhage has occurred, risk of further haemorrhage increases significantly.  Microsurgery, radiosurgery or embolization techniques used alone or in combination.