Not sure how to quote a quote so this will have to do.
Standard treatment for SSNHL is a tapering course of oral corticosteroids (prednisone or methylprednisolone). Since research performed at the Massachusetts Eye and Ear Infirmary in 1980 for demonstrated the effectiveness of this treatment, it has been widely used.
Even if it is MEEI, there is no link to the study. (I'm guessing it is
https://jamanetwork.com/journals/jamaotolaryngology/article-abstract/608834 which is widely cited.)
It's weird if this is settled, that it's still an area of significant study. There are indeed studies that show there is an effect (including apparently from 1980), and there are other studies that show there isn't. See here:
https://www.dizziness-and-balance.com/disorders/hearing/shl.htm for much more information and an extensive bibliography.
Their bottom line conclusions seem right to me: (direct quotes of 4 paragraphs from above link)
Bottom line: At this writing (2017) almost everything looks either ineffective or slightly effective. Because hearing tends to recover spontaneously at such a high rate, treatment is not always felt necessary, especially when impairment is minor. There is also an substantial possibility of bias, as it is difficult to "control" procedures that involve injections through the ear drum.
...
When a treatment of SHL is used, it often consists of
burst of steroids such as prednisone. There is an immense variability in otology/neurotology practice in regards to use of management and steroids for SHL (Coelho et al, 2011). 26% preferred oral steroids alone and 22% a combination of oral and intratympanic steroids. Some also used intravenous steroids.
...
Our impression from the literature is that systemic (i.e. oral or IV) as well as intratympanic steroids have a small positive effect on SHL. As of 2017, the best approach for hearing appears to be more steroids - -both systemic and intratympanic. Our guess is that larger and more direct doses of steroids (i.e. intravenous or high-dose prednisone) are slightly better than safer and lower doses of steroids (i.e. medrol dose pack). Lets be clear however -- these are not big effects, and
one should be careful to judge whether the risk of steroids is warranted by the small effect. For example, one would generally not want to use high dose systemic steroids in a diabetic, as the risk from steroid effects on diabetes might easily outweigh the small average effect on hearing. This involves an apples/oranges comparison however. The equation might be different in a professional musician with diabetes.
...
Bottom line: We recommend IT steroids in persons who cannot or prefer not to be given oral steroids, and in whom the time frame is short (i.e. 4 days from onset), and in whom the hearing loss is very significant. We do not recommend IT steroids otherwise -- for example, in persons with minor hearing loss. We are not sure ourselves whether oral or IT steroids are superior in terms of hearing results to doing nothing, but we are certain that large amounts of oral steroids can cause significant side effects. Concerning intravenous steroids, they are likely superior to oral steroids, but they are far more difficult to administer. Again, their use would seem most reasonable in persons with very severe hearing loss.