Kathy Griffin has detailed her mother's ''heartbreaking'' battle with dementia.

The 58-year-old comedian revealed 98-year-old Maggie has the disease - which causes a a decline in memory and makes it difficult to complete everyday activities - on Twitter on Thursday night (03.01.19), and admitted her health has ''rapidly'' declined in recent months.

The former 'Fashion Police' star says it has been ''particularly hard'' because her mom had a ''sharp mind'', and now she only knows her name and ''I love you''.

Alongside a picture of the pair and Maggie's dog Twinkle, she tweeted: ''As heartbreaking as this is, I feel the need to share some important info about my mom Maggie.

''I've always been honest with you all, but this one is really hard. The pic below, taken in September, was the last time I was able to have a proper/coherent conversation with her. Since that photo was taken, she has rapidly fallen into the throes of dementia. This is never easy for any child, I know this is a reality that millions of people deal with every year. But when it comes to my mom this is particularly hard because her sharp mind was everything.''

It has been ''devastating'' for Kathy to see her mother's memory fade so fast and she admits she is still coming to terms with her parent having the disease.

She said: ''My mom is 98 and up until this past couple years she was so sharp she always kept me on my toes.

''Her mind was so naturally quick, funny, and smart. No one could get anything past her.

''Watching that slip away so fast has been devastating. I want to assure you all that she is not in pain and she is getting the best 24-hour care.

''In terms of how she is now, at this point she only knows my name and I love you. I know many of you know what that reality is like...I'm still grappling with it.''

The 'Lovewrecked' actress used to regularly post photos of her mother and her beloved dog on social media, but she stopped sharing pictures after Maggie's health deteriorated.

She wrote: ''A big reason I'm sharing this news with you is that so many of you have asked why I haven't posted a video of Maggie & her beloved dog Twinkle in the past few months. Now you understand why we haven't been able to share anything, here is a moment between them from this summer.''