It’s a condition that affects more than 700,000 people in the United States, but most of us had never heard of normal pressure hydrocephalus, or NPH, until last week. Singer Billy Joel announced he has the disease and is cancelling a planned tour.

"Thank you for the outpouring of love and support," she wrote. "We are so grateful for the wonderful care and swift diagnosis we received."

Billy Joel has cancelled a string of tour dates after being diagnosed with a rare brain condition that affects his hearing, balance and vision.