Its not uncommon for people to say what youre saying, which is they are shocked at how rapidly a person can deteriorate. I hear it all. The. Time. And its totally understandable.The reality is he was slowly deteriorating before that episode, and you didnt notice it. People with early dementia are good st hiding it. We as doctors get used to picking up on the small signs but family doesnt always realize it. Ask them to recall something very specific, and they cant. But they keep light happy conversation very well. And they always seem happy and they say things are going well. In reality they dont remember much.Then something happens. They get sick with whatever and family is shocked at how it becomes full blown dementia. This is classic presentation for a UTI in the elderly. Something that little can make them completely confused.I suspect that was going on for him. You said he had a heart attack, his brain may have not gotten enough oxygen for a short but also, and that can cause permanent damage. You touched on sodium, Im sure you know correcting that has potential downsides as well.Regardless of what caused it, it is what it is now. Outside of it being one of his medications causing it, I suspect theres nothing you can do. Theres some medications they use to treat it, Im not familiar with them.Sorry youre dealing with this. Its hard to watch someone slowly slip away. Make sure youre taking care of yourself, a therapist can help often. And reading up on how to deal with dementia patients is helpful also, theres lots of small things to do that make both of your time together better
Based on the history you give I would be very surprised if he had not had imaging of his head either CT or MRI and this would certainly have identified if normal pressure hydrocephalus was the cause of his symptoms and this is important to rule out as if identified early it is treatable.It does actually sound pretty good for a history of dementia and I was unclear from your history whether he had in fact had a stroke as this can sometimes lead to a form of dementia known as vascular dementia which is common but presents slightly differently to the more common Alzheimers dementia. In vascular dementia the progression of symptoms tends to be step wise with sudden deteriorations followed by a plateauing of symptoms and then further sudden decline. In Alzheimers the decline tends to be more of a slow and subtle deterioration. You can actually develop seizures with Alzheimers disease which can develop relatively early in the disease but they can be treated with anti epileptics.Dementia cannot explain the hyponatraemia though; however from the history there are 2 common causes for hyponatraemia. Firstly your father was being treated for hypertension and quite a few of the medications used to treat high blood pressure can cause hyponatraemia. This increases if people are on multiple agents to reduce blood pressure and diuretics tend to be the worst but ACEi and ARBs also cause it. Secondly there seems to be some suggestion of alcohol use and at times you say your father was a heavy drinker. Alcohol particularly if drinking over recommended safe limits can also cause hyponatraemia as well as seizures. It is also a risk factor for developing Alzheimers disease and can actually cause a rarer form of dementia known as wernicke-korsakoff syndrome; although from the description you give I suspect this is unlikely to be the cause.