<human>: Can you succinctly summarize the text in 1-3 sentences?

I'm xposting this because this was a really sad and serious event for my family. If there has already been a post about this, please send me the link! If there is no theoretical conclusions, please tell me that, too..

Hey all, I hope someone can answer this question, because the event scares the shit out of me. My grandmother, who is 89 years old, was diagnosed with Alzheimer's ~6 years ago. According to what laymen's research I've done (I am certainly no neuroscientist), I can conclude that she is within the moderate-to-late stages of the disease; she can recognize us as family members, she has the ability to share stories from her past (though that ability is faltering), but she is absolutely dependent on caretakers for all activities and cannot put any memories into current context. Her phrases have become simple and she is certainly not the same soul who made me breakfast and sang me to sleep. She is the only case of degenerative mental illness in the family.

Recently, while being sat down for dinner, she suddenly started weeping. Despite depending on a walker, she got up without any assistance at all (including the walker), walked over to the sink to wash out her dish, and, still weeping, sat down in her recliner. She then began to lament about her confusion and started asking where her husband was. He passed in 2005. She also began to converse normally. My mother, terrified, helped her to the bathroom and put her to bed, and the next morning my grandmother awoke in her usual degenerative state.
This was also terrifying to me- I cannot imagine coming back to current reality after being in a state of somnombulance for years. How does this occur if current theories of Alzheimer's hypothesize that the brain has atrophied to a non-reversible state? Is there any narrative from the perspective of someone who's experienced this first hand? Any thoughts, info, etc is most-welcome...
<bot>: Though in her later stage of Alzheimer's, my grandmother has a sudden, though abbreviated return to "normal" capacity. Explain?