(NEXSTAR) – Billy Joel has canceled his upcoming shows after being diagnosed with a brain disorder known as normal pressure hydrocephalus, according to an online message posted to his social media channels.

“Under his doctor’s instructions, Billy is undergoing specific physical therapy and has been advised to refrain from performing during this recovery period,” the message reads, in part.

Normal pressure hydrocephalus is a condition caused by a buildup of cerebrospinal fluid in the ventricles of the brain, Johns Hopkins School of Medicine explains. Such a buildup could be the result of a number of factors, including a brain tumor, a brain infection or a head injury, but it’s more often diagnosed among........

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