The Wife With Alzheimers

From the Parsha Sheet - Rosh Yehudi:

My friend told me a story about an 80 year old man who came to a doctor's office for a treatment. He requested that they perform the treatment as quickly as possible because he is in a hurry.

During the treatment the nurse asked: "Where are you hurrying off to? Do you have an important doctor's appointment?"
"No, I am eating with my wife in the hospital?"
"What is wrong with her?"
"She has had Alzheimer's for a few years already."
"And if you are a little late, will she worry?"
"No, she does not understand what is happening to her. For the last five years she does not recognize anyone, not even me."
"And you visit her every morning even though she does not know who you are?" – the nurse said surprisingly.
"She does not know who I am," the man said smiling, "But I know who she is and who she was."