Christie Brinkley has sent her ex-husband Billy Joel well-wishes amid his battle with a brain disorder.

The 71-year-old model - who has daughter Alexa Ray Joel, 39, with the 'Uptown Girl' hitmaker - hopes her former spouse has a "full and speedy recovery" and is able to return to the stage, after he was diagnosed with Normal Pressure Hydrocephalus, which has caused problems with his hearing, vision and balance.

In a touching post, Christie penned on Instagram alongside a video of the family at a recent concert: "Dear Billy ,The whole Brinkley gang is sending you lots of love and good wishes for a full and speedy recovery . I was looking for some cute photos of you and Alexa to send you, when I came across this clip from a recent concert. It made me laugh ..but it also reminded me of all the joy you create, and all the sensational sing a longs you've lead… 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 And we all hope you're feeling alright!

We Love You, the kids, me and an arena or two!"

The message of support came just hours after Alexa Ray said her father "continues to regain his strength".

The 76-year-old musician revealed this week that he was diagnosed with Normal Pressure Hydrocephalus.

A statement posted on his Instagram read: "Billy Joel has announced that he will be cancelling all scheduled concerts following a recent diagnosis of Normal Pressure Hydrocephalus (NPH). This condition has been exacerbated by recent concert performances, leading to problems with hearing, vision and balance."

Billy is currently undergoing treatment and doctors have advised that performing would have an adverse affect on his health at this time.

The statement continued: "Under his doctor's instructions, Billy is undergoing physical therapy and has been advised to refrain from performing during this recovery period. Billy is thankful for the excellent care he is receiving and is fully committed to prioritising his health. He is grateful for the support from fans during this time and looks forward to the day when he can once again take the stage."

Billy added his own message to fans, saying: "I'm sincerely sorry to disappoint our audience, and thank you for understanding."

According to clevelandclinic.org: "Normal pressure hydrocephalus (NPH) is a condition that happens when cerebrospinal fluid builds up inside your skull and presses on your brain. This condition is most likely in people over 65. It's often treatable and sometimes even reversible."

Billy subsequently cancelled his tour, which included 17 dates in North America and England.

Alexa Ray provided an update on her Instagram: "SOUND UP. We love you and we got you, Pop!

"I just wanted to thank you all for the beautiful outpouring of love and support amid the recent news of My Father's health diagnosis." Alexa Ray continued. "My Dad is the strongest and most resilient man I've ever known … and he's entirely committed to making a full recovery with ongoing physical-therapy treatments as he continues to regain his strength.

"The genuine care, empathy, and concern from everyone means so much to him … it means a lot to me, too."

She concluded her post by sharing the lyrics to Billy's morbid 1993 track, 'Lullabye (Goodnight, My Angel)', which he penned for Alexa Ray.

She added: "Someday We'll All Be Gone / But Lullabies Go On And On / They Never Die / That's How You And I Will Be.

"The music continues… All My Love, Alexa Ray."

Billy also has Della, nine, and Remy, seven, with fourth wife Alexis Roderick.