There was a woman in the 90s who was brain dead and kept alive by life support for many years. It was controversial because her husband wanted to remove her feeding tube but her parents objected. Legally. Long drawn out legal battle from 1990 to 2005.

Anywho.

Here is an image of her brain scan. A CT. Not a MRI. But you can get similar info.

The dark areas are empty fluid filled.

White band around the head is the skull. Didn't know the skull could thicken with brain loss but I suspect that's a rare thing since people aren't typically kept alive that long with a shrinking brain.

Anyway.

You can see comparison of image taken in 2002 after being in her state (1990) for 12 years compared to an average brain of her peer (female of same age).

Her brain weighed about half as much as it should have.

She was finally allowed to die in 2005.

https://pmc.ncbi.nlm.nih.gov/articles/PMC558485/

https://en.wikipedia.org/wiki/Terri_Schiavo_case

Depending on your age and if you are in the U.S or not. You might remember hearing about her.