This is a public service announcement
So, it turns out that my MIL did not have a stroke last November after all. Based on what my FIL told DH, doctors found no evidence of a stroke in brain scans. Instead, she apparently developed Hyperosmolar Hyperglycemic Nonketotic Syndrome, or extremely high blood sugar from uncontrolled diabetes.
Her blood sugar was over 700 when she was admitted to the hospital. At that level, the blood becomes thick and syrupy. This makes the heart work very hard to move the blood and the kidneys work very hard to eliminate the sugar from the body. This also requires lots of fluid (for peeing out the sugar), which can lead to dehydration if it's not replaced.
Since she's stubborn and refused to go to the hospital when my FIL became worried, the condition eventually caused severe dehydration which, because the body was pulling fluid from wherever it could get it, including the brain, finally caused a stroke-like episode and brain damage. She is still in a nursing home and will probably never live at home again. My FIL did have a stroke last year; although he has recovered well, he can't take care of her by himself.
So please - if you think you have your diabetes under control, please make sure and check your blood sugar every day. My aunt had Type I diabetes and checked her sugar at least four times a day for 50 years. She still suffered neuropathy, kidney damage which required a transplant, eye damage requiring surgery, and wounds that would not heal.
Diabetes is a really nasty disease. Too many people underestimate it. Please take care of yourself.