Posterior cerebral artery aneurysms have been managed many a times conservatively.
However, in reality little really solid literature exists as to the subject
Here is a good review of the topic, and according to it endovascular management is the best option among all the three

Download powerpoint from this link
http://www.mediafire.com/?ek2nm5wwx4b

A 23 years-old man developed severe right sided proptosis a month after sustaining head injury in a road traffic accident.
His right orbit showed severe chemosis, injection with decreased ocular movement; vision had decreased to 6/18 ft.
Left eye was normal.
A DSA showed a direct type CCF with rent  near the posterior genu of internal carotid artery and vigorous antegrade flow into the cavernous sinus and ophthalmic veins.
GOLD BAL 4 balloon was used to occlude the fistula using a MAGIC coaxial system.
Post procedure angiogram showed complete occlusion of the fistula with immediate reduction in proptosis nad chemosis.
At 3 months patient 's appearance was totally normal with normal ocular movements but with vision still at 6/18 ft.