Billy Joel's daughter, Alexa Ray Joel, has revealed that the legendary singer has been diagnosed with a brain disorder and is doing well in physical therapy and losing weight. The news comes after he cancelled all upcoming tour dates due to the diagnosis of normal pressure hydrocephalus, which occurs when cerebrospinal fluid builds up inside the skull and presses on the brain, leading to issues with his balance, vision, and hearing. While he continues to focus on his health, musicians including Alexa Ray will perform at a tribute event at Carnegie Hall in New York City.