Severe chronic neck pain and headaches

Some years ago, I had major surgery on my brain that involved my head being held stationary at a difficult angle for 12 hours.  The surgery was very successful but I developed severe headaches.  Over the years I have tried many different pain killers, some of which changed my personality and affected my balance and ability to concentrate, three different physio’s, chiropractors, exercise with a trainer, acupuncture – British and Chinese – and hypnotherapy. All helped to a degree but nothing significantly.