Dane -- who shot to fame amid six seasons on the hit ABC drama "Grey's Anatomy," where he played Dr. Mark Sloan, affectionately known as "McSteamy" -- said his symptoms began over one year ago, when he began to experience weakness in his right hand.

Eric Dane told Good Morning America’s host, Diane Sawyer, about the experience he had before his diagnosis. He said he was experiencing weakness in his right hand, but credited it to being tired. Also,