This is how it happened: In 1983, I had nearly 9 hours of surgery to remove my cancerous thyroid, lymph nodes, and lots of surrounding tissue. Cancer had grown around my left side jugular vein. When the surgeon removed it, the vein burst. Somehow he fixed it, but I lost a lot of blood. I spent a long time in intensive care. Eventually, I recovered enough to confer with my surgeon. He said I'd probably suffer from nerve damage and maybe cognitive changes from such an extensive surgery. Right away, I discovered I couldn't talk. My left vocal fold (cord) was paralyzed. Months later, my friends noticed I was using my left hand while eating. I'm normally right-handed. Sure enough, as time went by, I used my left hand more than my right. I can now write left-handed as well as my right hand. And that is how I became ambidextrous.
I underwent 2 years of vocal therapy and regained my voice, though it is very low and hoarse.