It was after I had read a few things that linked Alzheimer's and vascular dementia that I began to have suspicions about dad's condition.

Before going into his particulars, the background seems to be that many dementia sufferers have at least some signs of both kinds of dementia. Those diagnosed with one kind are often found to have both, and the outward symptoms can be impossible to tell apart. Those with 'pure' Alzheimer's dementia can find their condition substantially worsened after heart attacks and vascular surgery. I may have the details wrong, but that is my understanding.

In dad's case, his cognitive condition worsened noticeably this year, but the evidence of his files showed that things really started to go wrong about two and a half years ago. Coincidentally, this is just when he went into hospital to have a pacemaker fitted.

Dad's blood pressure had been high for some time. I don't know when he started taking tablets for it, because back in those days he looked after his own medicine. He had begun to take the tablets only sporadically, and then almost not at all, when he started to suffer blackouts.

I never actually saw one of these blackouts happening, though Greg did. Dad had been standing watching Cassy's class perform at a school open day. He began to waver and buckle at the knees. Greg managed to grab him and steer him to a chair. On the other occasions he was always at church. I suspected it was dizziness brought on by standing too fast. One of my old lecturers said this was called Orthostatic Hypotension, I thought he was joking since this just means 'standing upright low blood pressure'. When dad's GP, Dr Femur, referred him to Dr Iliac, the local cardiologist, it was found that dad's response to the drop in blood presssure on standing was exactly the opposite of what it should be. Instead of his heart rate accelerating, it fell to about 15 bpm. Hence the pacemaker.

More recently, due to complaints about constipation, dad was examined by Dr Mandible, a gondolier of the alimentary canal, who detected, as other doctors had before him, an aortic aneurysm. Dad was then referred to Dr Anvil, a vascular surgeon and one of the least communicative characters in the planet. When mum, dad and I entered his surgery for the first consultation I noticed that there were only two chairs for the three of us. Dr Anvil didn't seem to sense the inadequacy of his office's seating. When I saw that he wasn't going to do anything about it, I looked around and spied another chair upside down on a treadmill. I asked him if my mother could use it.
'No,' he said.
I gave him another second to do something. When he didn't move, I walked back into the waiting room and picked up one of the chairs out there. We were by then playing a game, I thought. In silence, he looked at the scans I'd brought, examined dad, and then started writing. Mum caught my eye and almost giggled. It was like being before the headmaster. Eventually Dr Anvil passed me a sheaf of papers and explained the various tests we were going to have done. Then he did his party trick, which was to draw us a picture of the heart and main blood vessels, upside down. I refrained from remarking on this. Over the next couple of weeks I drove dad to and from his appointments. He had one overnight stay at a hospital, which evidently caused him some distress. When I went to pick him up he told me the story, as he saw it:

'I was just walking past this hospital, and I went inside to have a look around. Someone mistook me for a patient and took me upstairs,' he said.
'Really?'
'Oh, yes. It's quite incredible, really. They gave me a bed and food and everything. I kept telling them I didn't belong there, but nobody would listen.'
'That's amazing.'
'Well, I'm really glad you found me, Mike, because I could have been given an operation or something. They could have taken off a leg or a...'
'Bloody lucky escape you've had there, dad.'
He looked at me and smiled in a way that made me wonder whether he had been joking too.

The conclusion, after several weeks, was that despite the fact that dad had two large spherical aneurysms about the size of snooker balls, his aorta was a large one anyway, so the degree of enlargement was less than dangerous. Dr Anvil's advice was not to have surgery, but to follow up with annual checks. There is apparently a 10% per annum probability of one of these aneurysms bursting. Unless dad happened to be within metres of an emergency surgery at the time, this would probably be fatal.

Now, however, I think we have to be very cautious about committing dad to surgery. We need to consider the value of improving his survival prospects at the expense of worsening his mental condition. Both the surgery and the anaesthetic pose risks. I'm inclined to think that it would be better to keep dad as alert as possible and run the higher risk of a sudden death than to risk turning him into a mumbling basket case with a longer life expectancy.