Normal pressure hydrocephalus (NPH) is a rare, but reversible type of dementia. Early diagnosis can led to quicker treatment.

Billy Joel revealed he was recently diagnosed with normal pressure hydrocephalus (NPH), a rare, but reversible type of dementia. The statement notes that performing worsened some of the 76-year-old "Piano Man's" symptoms.

"The condition has been exacerbated by recent concert performances, leading to problems with his hearing, vision, and balance," the announcement said. "Under his doctor's instructions, Billy is undergoing specific physical therapy and has been advised to refrain from performing during this recovery."

NPH is a type of dementia that is not well known and often misdiagnosed, TODAY.com previously reported. In people with NPH, too much cerebrospinal fluid builds up in the brain and spinal cord. This accumulation of fluid leads to increased pressure in the brain and can cause problems with short-term memory, executive functioning and communication.

"Those symptoms are a little different than Alzheimer's," Dr. Mark Luciano, director of the Hydrocephalus and Cerebral Fluid Center and professor of neurosurgery at Johns Hopkins University, told TODAY in 2019. "In elderly patients that have a chronic form, it likely evolves over time."

Often doctors misdiagnose people with NPH because their symptoms mimic Alzheimer's or other types of dementia, Parkinson's disease or normal changes associated with aging. According to Johns Hopkins Medicine, signs of NPH include:

Johns Hopkins Medicine notes that people more likely to have NPH include:

Doctors diagnose patients by conducting an MRI of the brain to see if the fluid caused the brain's ventricles to become engorged. Doctors can perform a lumbar punction to remove some of the excessive fluid. Often, that eases some of their symptoms, according to past TODAY.com reporting.

People with NPH often undergo surgery where they have a shunt placed in their brain that allows the fluid to drain into their stomach where the body absorbs it. For many patients, this eliminates their symptoms.