She first thought the problem arose as a result of a tick bite, but was later diagnosed with the degenerative disorder � and she suspects she's had it for several years.

"I can't sing a note," Ronstadt tells AARP. "I couldn't sing and I couldn't figure out why. I knew it had to do with the muscles but I thought it might have also had something to do with the tick disease I had. Then I had a shoulder operation so I thought that's why my hands were trembling.