Dr. Jon LaPook joins "CBS Mornings Plus" to explain normal pressure hydrocephalus, the rare brain condition impacting Billy Joel's vision, balance and memory, and why it's often mistaken for Alzheimer's or Parkinson's disease.

The singer canceled his upcoming concerts because of the brain disorder. Here’s what to know about the symptoms, prognosis and treatment.

When fluid builds up around or inside your brain and inhibits typical functioning, it results in normal pressure hydrocephalus, or NPH, according to the Cleveland Clinic. This may lead to difficulties thinking and concentrating, as well as impair movement and memory. The condition may be reversible, and its symptoms could look a lot like dementia.