Brief Answer:
A common variation of the brain blood vessels.

Detailed Answer:
I read your question and I understand your concern as those terms might look scary. The image you have uploaded is not that helpful I am afraid as it has captured only the center of the page and you can't make out any complete line of text.

The brain is supplied by 4 main vessels, the carotid artery in the anterior part and the vertebral arteries in the back. So the brain area supplied by the carotid arteries and their branches is supplied by the anterior circulation (naturally the area supplied by the vertebral arteries is called posterior circulation).

The carotid arteries in the skull are branched into the anterior cerebral artery (ACA) and the middle cerebral artery (MCA) on each side. The anterior arteries do also communicate with each other through anterior communicating arteries.

The A1 is the first part of the ACA from it's origin to the point where it connects with the anterior communicating artery. In your case it is hypoplastic, meaning not well developed with insufficient blood flow through it.

However because the right ACA is connected to the left through the communicant artery it causes no problem as it takes its blood supply from the other side. That is why your doctor correctly said it was fine, there was no lack of blood supply. These variations are common and as long as the communicating artery does it job they don't cause any issues, it has been that way since you were born.

The early bifurcation of the right A2 (A2 is the part continuing after the A1), meaning it divides into its branches earlier than usual in its path, is a harmless born variation as well,, nothing to worry about as long as there is adequate blood supply.

As for the Flair hyperintense signals, it's difficult to speak without knowing how they look on sequences other than Flair and after contrast administration, however since they haven't changed from previous exam it is likely not a progressing process like a tumor or infection. Most probably ischemic changes for which attention to cardiovascular risk factors must be payed.

I remain at your disposal for further questions.

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Brief Answer:
Read below

Detailed Answer:
As I said before hyperintense signal of your white matter is generally related to ischemic changes to your small blood vessels. The changes seem to be diffusely spread (since they involve both the periventricular and subcortical white brain matter) but more pronounced in your frontal lobes. Most often these small vessel changes are related to factors like high blood pressure, diabetes, smoking, high cholesterol.

Hypoplastic right A1 segment means that the first part of your anterior cerebral artery is underdeveloped but since it receives blood by the left anterior cerebral artery it is not a dangerous change, it is a common born variation, found in as many as 10% of the people.
Proximal/early bifurcation means simply that the artery divides into its branches earlier in its course than usual. It is also a born variation which doesn't carry any damage.

I already tried to explain this in my first answer, I suppose it can be difficult to understand without any pictures, perhaps this scheme might help http://YYYY.com/YYYY

Bottom line is that you shouldn't worry about the A1 and A2 variations. Meanwhile for the white matter intensities, if you have the risk factors I mentioned you should treat them to prevent progression of those changes.

I hope to have been of help.

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