How fast can the progression of dementia be?

She should be tested immediately for a UTI. Don't wait until Monday.

Sudden declines can be caused by
1) An acute illness, such as a uti or other infection. When the illness is cleared up, the person will often return to baseline.
2) A reaction to a medication. Again, when the medication is discontinued, with a few exceptions, the person can return to baseline. (One of the exceptions is Haldol, if given to persons with LBD. It can cause permanent damage.)
3) Progression of the dementia itself. This is permanent. There may continue to be good periods and not-so-good periods. Some forms of dementia decline in a steady, gradual manner, but others "step down" in plateaus, with stable periods between changes that seem very sudden.

So, yes, dementia decline can be sudden. Or it can be caused by illness or medications. You have received some good advice on what kinds of things to check.

I'd like to share one other thought about declines. You may hear, even from medical professionals, that there is no recovery from declines. The decline is the new normal. In my experience that simply isn't true, as katiekay describes. If the decline is the result of illness or medication side effects the person is very likely to return to their previous level of functioning.

After each of his hospitalizations my husband (LBD) had home visits from therapists for a few weeks. Each therapist told me to except the decline to be permanent. They were wrong, but they weren't around long enough to see the recovery, so I'm sure they went about continuing to spread this false message. Hospitalization is NOT GOOD for anyone with dementia, although sometimes it is necessary under the circumstances. In our experience it took maybe a week or two to complete the healing process from whatever sent him to the hospital in the first place, and another few weeks to recover from the hospital experience. Home therapists were long gone at that point.

KathyMarie, please let us know how this works out for your MIL. We learn from each other.

My Nurses used to call these sudden changes "episodes". Something just happens. Mom could have had a stroke. Low potassium does a number on people too. Dehydration too.

That's too quick of a decline. She has to have more fluids. Get a urine test for a possible UTI. Get her to her dr asap. Not sure I'd go to ER. could pick up germs there.

Spitting a lot occurs often in some kinds of dementia. One cause can be excessive saliva because they forget to swallow. It will be interesting to hear what her doctor says!

My mother,97, recently gave us a scare. She could not walk, seemed way off. I made same day appointment with her doctor. After most of the day getting tests, we found the beta blocker had dropped her too low, her hemoglobin(needed iron supplements), and she was treated for pneumonia. This has taken over a month to get her navigating again. I am amazed that these took her down so quickly. Please, do not wait for Monday appointment, I am not sure our outcome would have been so good had we waited.
Bless you and your MIL

Kathymarie
I have read where Alzheimer's symptoms can come very fast but Jjariz makes a good point about UTIs. You can take her to ER or urgent care for a test and meds if positive or you can pick up a self test at the drug store. You would still need to see a dr for an antibiotic if the self test is positive.
If you haven't had experience with UTI in the elderly just know that it can be life threatening and the normal symptoms of burning etcetera will probably not be experienced. Use the search portion on this site and look for threads on UTI. Your MIL should be checked for one anytime you notice drastic change.
Talkey, my DIL father died of PD. He had those moments as well of clarity. Fleeting but treasured.

Thank you all so much for this great advise. We have already had her tested for a UTI and she doesn't have one. The results of her CT scan came back today and the result was Chronic Ischemic changes of the white matter. I am glad the neuro appointment is Monday so we know what the next step is. Does anyone know why she would constantly need to spit? I will let you all know what the doctor says.

KathyMarie, on a December evening of last year, my MIL went to bed able to walk with a cane and get up & down with some assistance. When she woke up the next morning she was unable to get out of bed without full assistance and was unable to walk without a walker. She had also lost her appetite, wouldn't eat much and had gone from moderate bladder leakage to complete incontinence. That is how fast it can happen. No UTI, no other illnesses. I would heed the advice of others, though, and have her checked out. We took my MIL to the ER just to be on the safe side.

My mother-in-law passed away from septice when the hospital was unable to detect the infection. I repeatedly told them something was not right and they repeatedly told me there was no sign of infection. She returned home and within 2 days a ambulance was called and she was brought to the hospital again and put in ICU and died 5 days later. She was completely septic. It seems when I researched it that the elderly often do not have elevated white blood count cells present during an infection because their immune system is compromised from years of antibiotics . Just wanted to put that out there that the hospitals and doctors don't know our loved ones Behavior as well as we do a sudden decline is very often infection that goes undetected .