musician plays his banjo while having brain surgery. (Two minutes of video of the performance.)

A musician who underwent brain surgery to treat a hand tremor played his banjo throughout to test the success of the procedure.
Eddie Adcock is one of the pillars of Bluegrass Music and realised his tremor could threaten his ability to perform professionally.
Surgeons placed electrodes in Mr Adcock's brain and fitted a pace maker in his chest which delivers a small current which shuts down the region of his brain causing the tremors.

(link thanks to Bob Morales)