I don't have much too add beyond what has been said. I can find little in Medscape online literature on the association of cerebral AVM and diving. There is a lot on pulmonary AVM and diving, which can be genetically (rarely) associated with the brain variety --- pulmonary AVM are like PFOs, allowing venous air to enter the cerebral circulation.
In the brain, however, the blood is shunted from arterial to venous, although there still is a direct shunt between the arterial circulation and the venous, so the risk of AGE may be higher theoretically.
Like aneurysms, AVMs have a yearly bleed rate of 1-3%, but AVM hemorrhages are much less dangerous, in general (although they can still do damage). Unllike aneurysms, AVMs tend to be epileptogenic. The risk of diving should be no more and no less than the risk of any other seizure disorder in this regard.
HOWEVER, AVMs are very sensitive to carbon dioxide vasoregulation. The chief theoretical risk of diving is likely the effect of CO2 retention and/or jugular compression from wetsuits/equipment etc, leading to higher risk of AVM rupture. They can be fragile things, as I have experienced first hand. The contraindication of nitrox is mystifying, but seems moot if they don't let you dive.
The good news is that these lesions can often be obliterated with non-invasive radiosurgery or, if necessary, open surgery or embolization (or a combination of the three). The right occipital lobe is not the best place for an AVM (right frontal is better), but certainly isn't the worst. Thus, the situation may not be permanent at all.
The indication for treatment is the production of symptoms (seizure, headache. visual loss, hemorrhage), which seems to be the case here.
Obviously, only your own physicans can advise you of how to treat this and whether you should dive or not.
