John Driskell Hopkins has been diagnosed with ALS. The 51-year-old musician - who is best known being part of the the Grammy Award winning group Zac Brown Band - is suffering from muscle disease Amyotrophic Lateral Sclerosis, which causes a progressive degeneration of motor nerve cells in the brain He said: "Over the past several years, I've noticed some balance issues and some stiffness in my hands. After careful analysis by some of the country's top neurologists, I have been diagnosed with ALS.