The autograft you speak of is the act of diverting a scalp artery into the brain and hooking it up to an intracranial artery. This was typically done to hook the superficial temporal artery (the big thumping artery in front of your ear) to the middle cerebral artery (the main branch of the carotid in the head). This STA-MCA bypass was intended to prevent strokes in patients with hardened carotids in the neck, but has been largely abandoned due to a 1985 report that found it was, essentially, usless or even worse than useless. (I wrote an article about this sad chapter in brain surgery for Discover magazine about ten years ago...it was sad because the operation was done for 20 years on hundreds of thousands of patients worldwide before someone actually did a large study of the results. The operation was fun and very lucrative and surgeons were not anxious to find out it didn't actually do anything. It is still used on very rare occasions, but the indications for such bypasses are very few.)
In this case, the artery bypass would be from the occipital to the posterior cerebral, about which even less is known. The bypass only has a chance of working if the flow rate in the brain artery is far below normal, otherwise no blood will be shunted and the bypass will clot off. In this case, without a functional blood flow test (like a xenon study), we don't even know if the vascular anomaly here is actually compromising blood flow at all.
In people with STA-MCA bypasses, I should note, scuba would be impossible. These patients were not allowed to wear hats postoperatively, for fear of compressing the scalp artery bypass, let alone a scuba mask strap.
