Terry Crews‘ wife — Rebecca King-Crews — is going public with a shocking medical diagnosis … revealing she’s been living with Parkinson’s disease for years.

Terry and Rebecca made the surprising announcement on the “Today” show Monday … saying she was first diagnosed with the disease in 2015.

Rebecca says she recently underwent a breakthrough procedure to help with symptoms on the right side of her body … and it’s already making an incredible difference. She can now write with her right hand for the first time in nearly three years … even writing her name and dates again.

As for why she’s speaking out now … she says she’s incredibly encouraged by the results of the procedure, calling it a “new frontier in medicine” — especially since doctors were able to operate on her brain without cutting her open. She hopes it becomes more widely available … noting it’s still expensive and not yet covered.

Terry says Rebecca kept her diagnosis under wraps because she didn’t want pity … but they felt it was time to share and raise awareness.