LiveLeak: A musician who underwent brain surgery to treat a hand tremor played his banjo throughout surgery to test the success of the operation.

WikiPedia: In October 2008, concerns about hand-tremors, which could have compromised his performing career, led to Eddie having brain-surgery. A local anaesthetic was used during the surgery, and he was encouraged to play banjo during the procedure in order to check the effectiveness of the treatment. During the brain implantation surgery, the patient is kept conscious so they may assist the doctors in properly placing the leads. They do this by experiencing its immediate effects on their fine motor skills. In Eddie’s case, this would be his right hand picking the banjo. Eddie has related that this was not an easy process to experience.

"I came up in music the hard way and learned to be a trouper fast. Some of those early days were pretty rough, and I’ve been stomped, cut and kicked; but I never went through hell like this — it was the most painful thing I’ve ever endured. And it was risky. But I did it for a reason: I’m looking forward to being able to play music the way I did years ago prior to getting this tremor. It means that much to me. I’m far from being done!"