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.

"I feel like maybe a couple, few more months, and I won't have my left hand either," the 'Grey's Anatomy' alum said, adding that he worried about losing the use of his legs, in a sobering interview that aired on Monday's 'Good Morning America.