Billy Joel has been forgetting lyrics for at least a decade, it was revealed today, after he announced he was having to cancel all planned concerts due to a brain disorder.

The Piano Man singer, 76, took to Instagram on Friday to share that he has been diagnosed with normal pressure hydrocephalus (NPH).

The condition has impacted Joel's 'hearing, vision, and balance,' according to the social media post.

A spokesperson for the singer said that his condition had been 'exacerbated' by recent performances. He is now taking a break and undergoing 'physical therapy' to treat the condition.

Normal pressure hydrocephalus is caused by too much fluid collecting in the ventricles, or spaces in the brain and spinal cord, putting pressure on these areas and triggering its symptoms, including struggling to walk, an inability to control the bladder and memory problems.