Christie Brinkley Sends Heartfelt Message to Ex Billy Joel Amid Brain Disorder Diagnosis

Christie Brinkley is showing her support for ex-husband Billy Joel following the news of his recent brain disorder diagnosis.

Brinkley took to Instagram on Saturday to share a touching message alongside a video clip of her and daughter Sailor Brinkley-Cook from one of Billy's past NYC concerts.

She started the post by sharing that the entire Brinkley family is sending him lots of love and good wishes for a full and speedy recovery. She noted she's been reminded of all the joy Billy creates.

She praised the singer's ability to bring people together through his music writing ... "You turn an arena of strangers into a living room full of friends as we all sway in unison. I’m sure I’m speaking for everyone in that room when I say please take good care of yourself -- we all want you back in that white hot spotlight. You’re OUR Piano Man and we’re always in the mood for your melodies."

She closed the post with a warm message of love and encouragement saying ... "And we all hope you’re feeling alright! We love you—the kids, me, and an arena or two!"

The former couple was married from 1985 to 1994 and share daughter Alexa Ray Joel.

The singer announced on Friday he is suffering from Normal Pressure Hydrocephalus ... which is a brain disorder where excess fluid accumulates in the brain's fluid-filled cavities. Billy says his condition has been exacerbated by his recent concert performances ... and he's having trouble hearing, seeing and balancing.