It is considered idiopathic, @jakedduck1. That means they are not sure why. I had surgery 5 years ago at Cleveland Clinic and a Silastic implant was put in the paralyzed cord which helps it close up with the other cord. I have a stronger voice now, I don't choke as easily when eating, however, I still do need to eat slowly and chew food more than typical. I still can choke on occasion but basically much better than before the surgery.

Prior to the surgery, I sounded like I had laryngitis by about 1 p.m. Now I only sound that way if I get very tired.

Yes, speech therapy does help as well as singing. I also use a device that helps strengthen the cords.