I went back to the doctors today to discuss the saga of the miniturised submarines poking about in my brain; the discussion boiled down to the simple facts:

If I have the scan and they find something worth operating on they will want to operate (why else do the scan?). There will then be a 20% risk of something happening. 'Something happening' being anything from me having a mild, recoverable stroke, to being 100% irrecoverably dead.

If I have the scan and they find something and I don't have anything done about it there is a 10% risk of the same 'something happening' in my lifetime. ie anytime between now and when I die, from whatever cause, which could be anything up to 40+ years from now. (Optomist)

If I have nothing done there is nothing I can change about my lifestyle that will make a blind bit of difference. If it is going to happen it will happen. All that will change if I know about it is I will be concious of the fact that I have an aneurism and all the attendant worries that will bring.

I think I am going pass on having the scan. Sometimes, ignorance is bliss. The maths has convinced me that this is one of those sometimes.