Christie Brinkley shared that her ex-husband Billy Joel is on the mend almost a year after being diagnosed with the rare brain disorder normal pressure hydrocephalus (NPH).

The model told Hello! Magazine on Tuesday, “He’s doing very well.”

The disorder occurs when cerebrospinal fluid (CSF) builds up inside the skull and presses on the brain, disrupting cognitive functioning.

Christie Brinkley (pictured here on Tuesday) shared that her ex-husband Billy Joel is on the mend almost a year after being diagnosed with the rare brain disorder normal pressure hydrocephalus (NPH). Getty Images for City Harvest

The model (pictured here with the singer in 2011) told Hello!…