Never having heard of such a thing, I immediately consulted Dr. Google. I searched on sudden hearing loss and was gratified to discover that the syndrome is called Sudden Hearing Loss, thus proving once again that great minds think alike. Dr. Google said to treat it as an emergency so I saw an ear specialist that afternoon.
Short synopsis: the docs think this is usually caused by a virus, though there is apparently some debate about this. It is often confined to one ear, though there are exceptions. Hearing usually returns, though this can take weeks or months. There is no medical cure for a viral infection (cf. the flu or the common cold), so the docs tend to prescribe steroids to boost the body's natural resiliency. Beyond that, as with any viral infection, your body will eventually fight it off, or not. With sudden hearing loss, the vast majority of patients recover their hearing. There may be some permanent degradation, usually slight but sometimes significant. No point worrying about it as there is nothing you can do about it, and the odds are greatly in your favor. In my case, I took the steroids in pill form; no needles, which is vastly more civilized. My hearing returned over the period of a few weeks.
Thanks for your experience.
That should give my wife some hope for getting at least some of her hearing back.