92 year old dad showing signs of dementia inconsistently. Why is it sporadic?

You should send a note to the doctors office and explain all the inconsistencies that you have noticed.
There is a condition where Spinal Fluid backs up in the brain (hydrocephalus) and in an older person some symptoms are very much like some forms of dementia
Even if this is a long shot. (the old saying when looking for a diagnosis..if you hear hoof beats think horses not zebras...well sometimes it is a zebra)
Most doctor's offices have a Patient Portal where you can send notes and ask questions. This could be done without your dad realizing. But...my opinion here..if you are with your dad during these visits you are acting as his advocate all you are trying to do is make sure he gets the best care possible there is no intention of embarrassing or insulting him.
Also not that you asked but even I have heard (no pun intended) of Musical Ear Syndrome (and I just tried this..Google "Musical Ear Syndrome" and you get in 0.74 seconds 6,480,000 results. you might want another audiologist...one that knows how to Google)

In the”Good Old Days” electric cords were made in layers and pieces. If you pulled a plug out of the socket. the wire could be moved in the plug, and the off and on disruption in electricity could cause an interruption of power to a lamp or radio which could then cause a slight blinking of the light, or intermittent interruption in the sound.

Some dementia patients seem to have short circuits in their thinking. Sometime everything works OK, but if the “wiring” is just a little off, full blown dementia is apparent.

If you haven’t considered an exam by a specialist with training in identifying dementia, it may be a good time to start searching for someone.

His medical doctors can help direct you to local specialists in psychiatry, psychology, and other specialist who can give you a sense of where he’s functioning now, and how to deal with any issues that may come up as his condition progresses.

You need to get a referral to a neurologist. He/she will be able to determine if it a dementia or TIAs causing the problem. The uneven gate thing bothers me.

With my Mom I kept notes on my computer about new things going on and her progression. Then I organized these notes in a short note to the doctor. A paragraph for each different thing. I typed in in large font, 14 or 16, so it was easy to read. Kept each paragraph short and simple. One page only. This way when we when in for the appt. the Doctor could ask questions based on what I wrote. And he did refer to my notes.

People with Dementia in the early stages can "showtime". This means they are aware they are having problems, and for a short period they can act normal. So giving your notes to the receptionist and asking that the doctor read them before your appt will help with a doctor's diagnosis.

My dad had vascular dementia. It definitely came and went.

I like Grandma1954's advice. Inform his doctor of what you've observed and see if he can be helped.

My moms cognitive “sharpness” as we call it Can vary a great deal based on how rested her brain is so how she slept and time of day, how much water she has had (it is so easy for us to be dehydrated without realizing it as we age and our activities lessen) and other medical factors, she is diabetic and somewhat prone to UTI’s which is immediately noticeable in her cognitive function. It’s been this way for several years now since her stroke and probably before we just didn’t notice. So I think it can be a combination of things including of course dementia simply getting worse. I also echo others thoughts of possible TIA’s and it should all be checked out. As things open up a bit more this should become a bit easier but getting a full neuropsych evaluation would be a great thing to do, dementia or not, simply as a baseline to be able to use as a marker for possible future changes. It can easily be explained to him as an important way to keep future events from simply being attributed to dementia, something easy to do with elders and identifying medical things that can be remedied or helped rather than written off. The goal here is quality of life. The exam will also give you a better idea of where his dementia is and what areas or things can be done to slow it down or work with it and it’s a fact that having a baseline to start from is a tremendous help in the future. I wish we had had one for Mom before her stroke (she has been left with aphasia) to better identify what is dementia and what is aphasia.

Also make sure he doesn’t have UTI or some other underlying infection, get a blood work up to make sure there isn’t a deficiency or surplus throwing things off, it can also tell them something about heart issue and pay some attention to how much water he is getting and the affects, if there are any, the exercise he gets or doesn’t and if there is a particular time of day things decline or if his sleep affects it. These are all things you can control to some degree and he might even grasp in his sharper times and hear our brains become more sensitive to these changes as we age.

I don't know where you live but people with Dementia and Alzheimer's often get a little cold and don't always respond to the heat and don't always want to take a shower i.e. People can get like this in the evening. A Yogi tea brand I used to buy my dad of a Calming tea that had Gotu Kola in it and it helped, but I don't see it around our grocery stores anymore. It helps the circulation to keep them warm and less Dementia shows up usually then. Greens like lettuce, Spirulina and such often help them, too. Sometimes they need a sip of a Detox shot i.e or sometimes they may need a mug of organic Black Tea; you can even add a bit of organic milk to help their brain, to the organic Black Tea and a little honey or organic sugar if they want, just 'to taste' or get the bitter out of it, and that would help them. There are movies that show that if someone can draw a picture of a clock correctly, they don't have Alzheimer's - a round clock with digits, like we hang. Hope that helps.

Is it definitely dementia - we have this with my 92 year old mother, but they think its TIAs as she can be fine for a while then totally incapable mentally and poor physically, lack of balance, lack of strength, can't walk can't remember our names. It goes in cycles, but each "down" cycle leaves her slightly less able in all ways.

If you have an audiologist who's never heard of Musical Ear Syndrome, I'd say it's time to find a new audiologist!! Or just say To Heck With It entirely, and let him alone with the singing voices! MES has to do with hearing loss, and nothing more insidious than that, fortunately.

If someone cannot draw a picture of a clock showing a certain time of day, say 8 o'clock, it means they are having an issue with their Executive Brain Function. The Executive Brain function is like the conductor of the orchestra....if it is compromised, the players have no idea WHAT to do or WHAT is going on. A compromised Executive Brain function indicates dementia and/or Alzheimer's is going on. My mother was diagnosed in 2016 and her version of a clock was a blob......and didn't resemble a clock in any way, shape or form. She was also having a lot of trouble with everyday tasks and remembering things in general. But it showed primarily that she was unfit to live alone and needed help with ADLs.

While she's declined cognitively since 2016, she still has times where she is perfectly lucid, tricking many people into thinking she's fine & dandy. Like WHY are YOU here in a Memory Care facility??? There is obviously nothing wrong with you! Ha. That is known as Showtiming, and my mother wins the Oscar Award for that talent year in and year out. She can make great small talk, relying on embedded memory of old chit chat learned years ago, and sound like she's 100% normal. In fact, she's been very lucid in general the past 3 weeks, coming off of a few month period of word salad and general confusion and misery 24/7.

My point? The confusion comes and goes. Each day is different, keeping everyone (including the patient) completely off kilter and not sure WHAT'S going on. Which is one of the reasons dementia sucks SO bad and robs everyone in its path of a good life.

Keep your dad comfortable and as happy as possible, that's my suggestion. Don't drag him back & forth to tons of doctors for lots of different medications and diagnoses. For what? To extend his life by a short while? Instead, allow him the privilege of enjoying to the fullest what's LEFT of his life. Dementia and CHF and lower bundle blocks (my DH just had a pacemaker put in last July for that, by the way, after fainting and falling off the back of a truck, but he's 62) and kidney disease will rob him of his life anyway. Why wreck what's left of it with doctors and needles and tests and all that crapola?

When my dad was 90, he fell and broke his hip. At that time, we found he had a brain tumor via an MRI. He hated that test SO much, he was SO stressed out and traumatized by it, that I promised him Never Again Dad. And I stuck to my word, right to the very end of his life when it became necessary for another MRI to keep him at his ALF with hospice. I was told to get him an MRI every 3 MONTHS. And I said WHAT FOR? He was living his last days as it was. Why stress him out further?

So he lived the last 11 months of his life in peace and happiness with my mother, never realizing his brain tumor was killing him. And after his last MRI at the ER, the tumor took his life in 19 days. He was kept totally comfortable with hospice care, and I will be forever grateful for the route we took with him.

Allow your dad's last days to be as peaceful as possible, my friend. Bless you for all you're doing, and for giving him a dignified life, right to the very end