How do doctors diagnose Dementia?

His family should know if he has dementia. If they don't think he has? Then he doesn't. Dementia, except in its mildest forms, is hard to miss. At first, we chalk up aberrant behavior as forgetfulness. Then, "Look at dad; he's a little confused." But soon, there's no missing it, in my opinion.

I'm sure some families can be in denial, but really . . . it's pretty hard to miss.

And, yes, a doctor can misread a patient and/or just be totally wrong. He saw, what? A ten-minute snapshot? Whoever's living with him knows much better than he.

The parts of the brain most often affected in NPH are those that control the legs, the bladder, and the "cognitive" mental processes such as memory, reasoning, problem solving, and speaking. This decline in mental processes, if it is severe enough to interfere with everyday activities, is known as dementia. Other symptoms include abnormal gait (difficulty walking), inability to hold urine (urinary incontinence), and, occasionally, inability to control the bowels.
Does he have any of these?

You're SUPPOSED to do an actual objective evaluation - at least a mini mental status - rather than just go by global impression. And you take a history from the patient and from the family. If it does not gibe you need objective information before you either blow it off as greedy kid trying to get money or decide that at this age, senility must be setting in. AND part of the evaluation is a decent search for treatable causes. Docs who don't do this properly are vulnerable to being fooled by a great case of "Show-Timer's" OR a truly greedy or overprotective kid, and could miss hypothyroidism, depression, alcoholism and several other things that need attention. And docs who either aren't comfortable doing the serial sevens, checking orientation, draw a clock and spell world backwards tests should refer, and should refer in any event for something more formal if the diagnosis is in doubt.