Piano man Billy Joel said the brain disorder he's battling "sounds a lot worse than what I'm feeling."

RadarOnline.com can reveal, in May, Joel was diagnosed with normal pressure hydrocephalus – NPH – a buildup of spinal fluid inside the brain, a condition that can affect hearing, vision and balance, according to MedlinePlus. Article continues below advertisement

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"I feel fine," the 76-year-old hitmaker said on Bill Maher 's Club Random podcast, though he added balance has been his biggest challenge so far. "My balance sucks. It's like being on a boat," he explained. Article continues below advertisement

Although he said doctors don't know what caused his condition, the

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